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Last Updated :2024/11/12

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Master

Affiliation (Master)

  • Faculty of Engineering　Civil Engineering　Natural Disasters and Adaptation

Affiliation (Master)

  • Faculty of Engineering　Civil Engineering　Natural Disasters and Adaptation

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Profile and Settings

Profile and Settings

  • Name (Japanese)

    Watanabe

  • Name (Kana)

    Yasunori

  • Name

    201301082888180203

Alternate Names

Achievement

Research Interests

  • 混相流   乱流   砕波   水工水理学   気泡   減災   浮遊砂   画像計測   水中音   海岸工学   ジェットの分裂   砕波乱流モデル   固気液混相流   海洋科学   wavelet packet   衝撃砕波力   気泡音   Large Eddy Simulation   砕波乱流   計測工学   bubble clouds   3次元的水粒子軌道   斜行渦   混入空気   高波数遷移   3次元的大規模渦   Stereo PTV   3次元大規   波浪   防災   

Research Areas

  • Social infrastructure (civil Engineering, architecture, disaster prevention) / Hydroengineering

Research Experience

  • 2019/12 - Today Hokkaido University Faculty of Engineering
  • 2008 - 2012 北海道大学 工学(系)研究科(研究院) 准教授

Published Papers

  • Yasunori WATANABE, Yuichiro SUZUKI, Shota SAITO, Ayumi SARUWATARI
    Japanese Journal of JSCE 80 (17) n/a - n/a 2024
  • Shota SAITO, Akihiro NOMURA, Ayumi SARUWATARI, Yasunori WATANABE
    Japanese Journal of JSCE 80 (17) n/a - n/a 2024
  • NOMURA Akihiro, ISHIKAWA Hiroki, SATO Noriyuki, HAYAKAWA Tetsuya, IWASAKI Shinsuke, OTSUKA Junichi, MORI Nobuhito, WATANABE Yasunori
    Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering) 公益社団法人 土木学会 78 (2) I_487 - I_492 2022 
    Sea level rise expected during climate changes is one of the important issues in future coastal protection. To estimate the sea level at coast with tectonic activity, the observed sea level records need to be collected with the ground displacement. This paper presents a regression analysis of the sea level rise estimated by tidal records collected with ground level observations along coasts of Hokkaido. The error analysis provides conditions to extract available datasets observed at local sites with tectonic displacements. Future projections of the current estimations are consistent with predictions by the previous climate-ocean models, which ensures appropriate analysis for future sea level rise.
  • Yasunori Watanabe, Haruhi Oyaizu, Hisashi Satoh, Yasuo Niida
    INTERNATIONAL JOURNAL OF MULTIPHASE FLOW 136 0301-9322 2021/03 
    Air bubbles entrained in ocean breaking waves play various roles in air-sea gas transfer, wave energy dissipation, and surface layer mixing. While sub-mm bubbles dominate the distribution of sizes observed in bubble plumes created by breaking waves, the dynamics of such microbubbles in a swarm are poorly understood, and most previous experimental and computational studies have focused on the behavior of homogeneous swarms of larger mm-scale bubbles for industrial applications. Here, we propose novel probabilistic empirical models of rise velocity and bubble drag for a microbubble swarm incorporating bubble- vortex interactions. These are based on image measurements of the motion of electrolytically generated microbubbles. We found that convective interactions between bubbles and vortex-induced flows, that is, Rayleigh-Taylor instability caused by density difference near the electrodes, induce counter-rotating vortices that accelerate bubbles and align them along paths in the flow induced between them, resulting in an increase in rise velocity and its variance in the statistical equilibrium state. We describe the statistical features of bubble rise in such swarms in our proposed empirical model and deduce its optimal parameters. We anticipate our findings being a starting point for understanding behaviors of oceanic bubbles possessing an analogous size distribution to the present electrolytically generated microbubbles.(c) 2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )
  • 小林 正法, 猿渡 亜由未, 渡部 靖憲
    土木学会論文集. B2, 海岸工学 Journal of Japan Society of Civil Engineers. Series B2, Coastal engineering / 土木学会海岸工学委員会 編 土木学会 77 (2) 3p  2021 [Not refereed]
  • WATANABE Yasunori, OGUMA Takashi
    Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 公益社団法人 土木学会 77 (2) I_31 - I_36 1884-2399 2021 [Not refereed]
     
    In this study, a theoretical frequency condition to create the focusing wave packet in uniform current is proposed and validated through wave-current experiments. We observed the maximum surface elevation monotonically increase with the current velocity and the highest elevation of six times higher than the initial wave amplitude is recorded at the highest current velocity in the present experimental conditions. We also found the temporal variations of the spectrum width during the focusing process and the nonlinear steep wave form with double harmonic component at the focusing location.
  • WATANABE Yasunori, WATANABE Kenta
    Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 公益社団法人 土木学会 77 (2) I_43 - I_48 1884-2399 2021 [Not refereed]
     
    In this study, the novel LES-Stochastic model describing bubble rise, bubble-interface interactions, bubble cluster formations, coupled with turbulent fluid motion, has been proposed. The foam model, developed on the basis of the analytical solution of bubble-bubble mechanical interactions by Nicolson (1948), reasonably simulated oscillatory bubble behaviors beneath the interface and formations of the bubble clusters. These processes create additional turbulence near the interface and thus enhance surface renewal, which may contribute material transport between air and water.
  • KANETO Toshimichi, KIMURA Tatsuto, WATANABE Yasunori
    Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 公益社団法人 土木学会 77 (2) I_229 - I_233 1884-2399 2021 [Not refereed]
     
    Kaneto et al. proposed a method to evaluate possible future tsunami caused by submarine landslide. However, superposition with tsunami caused by active faults, which is likely to cause submarine landslides, has not been investigated. This study focuses on the distribution of tsunami arrival times within a radius of 100 km from the Kashiwazaki-Kariwa Nuclear Power Station, proposes a method for determining the combination of tsunamis caused by submarine landslides and active fault. In addition, we evaluated the maximum water level due to the superimposed tsunami by the linear addition method of the tsunami numerical simulation and the method by coupled analysis, and it was confirmed that there was no significant difference in the tendency of the analysis results by either method.
  • Ayumi Saruwatari, Yasunori Watanabe
    Proceedings of the Coastal Engineering Conference 36 (2020) 0161-3782 2020/12/31
  • Takuya Inoue, Yasunori Watanabe, Toshiki Iwasaki, Junichi Otsuka
    EARTH SURFACE PROCESSES AND LANDFORMS 45 (12) 2897 - 2911 0197-9337 2020/09 
    Antidunes are fluvial bedforms that form in rivers with supercritical flows. The water surface over antidunes is strongly in phase with the bed surface, and the water surface is amplified to produce large surface waves. Many experimental studies have addressed antidunes; however, the shapes of three-dimensional antidunes in a wide channel with alternate bars have not yet been appropriately understood. In this study, we experimentally investigated the streamwise and transverse length scales of antidunes under conditions with a large width-depth ratio. Our experimental results provide evidence for the coevolution of antidunes and free alternate bars, and show for the first time that the development of free bars greatly alters the three-dimensional shape of water surface waves over antidunes. In the absence of free bars in a wide channel, multiple longitudinal wave trains form, and the number of wave trains counted in the transverse direction increases with increases in the width-depth ratio. However, the presence of free bars affects the local flow characteristics, resulting in a decrease of the number of wave trains in the transverse direction. Therefore, we propose a simple model for predicting the reduction in the number of wave trains by combining two previous theories for antidunes and free bars. Results obtained by the model were found to largely agree with experimental observations. (c) 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd
  • Yasunori Watanabe, Yosuke Tsuda, Ayumi Saruwatari
    Coastal Engineering Journal 62 (2) 336 - 349 2166-4250 2020/04/02 [Refereed][Not invited]
     
    In coastal engineering, as shoaling waves break in shallow water, most wave-breaking research has been focused on depth-induced wave breaking. However, violent wave breaking under storm conditions may be caused by superposition of many shoaling wave components. In order for simulating extreme waves in open ocean, theories to focus wave-packets, assuming that wave speed of each wave component is unchanged during propagation (i.e. deep water or shallower water without bathymetry changes), have been derived, while shoaling effects of the focusing process in shallower waters have not been considered in the previous studies. The extension to shoaling coastal wave-packets may aid in simulating extreme coastal wave breaking under violent storm conditions via laboratory experiments. Here, we derive the general wave-packet focusing conditions for arbitrary water depth. The proposed conditions were used to simulate shoaling wave-packet focusing on flat and sloped bottoms in shallow water experiments for validation purposes. The effects of depth-induced wave breaking in the focusing wave groups are discussed in this paper. The current focusing technique can fully control the focus location and time in wave experiments with an arbitrary bottom structure, which may be useful for further extreme wave research in coastal engineering.
  • 金戸俊道, 山本和哉, 木場正信, 木村達人, 西愛歩, 渡部靖憲
    土木学会論文集 B2(海岸工学)(Web) 76 (2) 1883-8944 2020
  • 渡部靖憲, 野中拓実
    土木学会論文集 B2(海岸工学)(Web) 76 (2) 1883-8944 2020
  • 渡部靖憲, 小嶋亮太
    土木学会論文集 B2(海岸工学)(Web) 76 (2) 1883-8944 2020
  • 渡部靖憲, 土屋裕嵩
    土木学会論文集 B2(海岸工学)(Web) 76 (2) 1883-8944 2020
  • 猿渡亜由未, 小林正法, 高須賀啓孝, 小山裕文, 高橋幹夫, 山下孝行, 樋口益盛, 渡部靖憲
    土木学会論文集 A2(応用力学)(Web) 76 (2) 2185-4661 2020
  • Yasuyuki Baba, Teruhiro Kubo, Nobuhito Mori, Yasunori Watanabe, Tomohito Yamada, Ayumi Saruwatari, Junichi Otsuka, Yusuke Uchiyama, Junichi Ninomiya, Tomoya Shimura
    22nd Congress of the International Association for Hydro-Environment Engineering and Research-Asia Pacific Division, IAHR-APD 2020: "Creating Resilience to Water-Related Challenges" 2020 
    This paper shows some observation results on high wave condition due to typhoons measured at an offshore observation tower. Japan is affected by typhoons every year, and some typhoons cause serious damages in Kii peninsula and its surrounding areas sometimes. In 2018, three typhoons (No.20, 21, 24) approached around the Kii peninsula, and the severe wave conditions caused by the typhoon Jebi (No.21) and the typhoon Trami (No.24) are observed at the observation tower of SOO. During the typhoon Jebi and the typhoon Trami approaching, the maximum significant wave heights reach 9.60m by the typhoon Jebi and 11.09m by the typhoon Trami, respectively. On the other hand, wave condition caused by the typhoon Cimaron (No.20) is relatively milder than the ones by the typhoon Jebi and the typhoon Trami, even though a central atmospheric pressure and the distance between the center of the typhoon and the observation tower are similar to those of the typhoon Jebi and the typhoon Trami. In case of 2018, it is pointed out that the magnitude of high wave condition is associated with the offshore wave direction around Kii peninsula because the observation site opens to the south-west (between about 190deg and 240deg). In this paper, the factors and backgrounds related to high wave conditions by typhoons are discussed based on the observation results including other typhoon cases.
  • Ayumi Saruwatari, Masanori Kobayashi, Nobutaka Takasuka, Hirofumi Koyama, Mikio Takahashi, Yasunori Watanabe
    22nd Congress of the International Association for Hydro-Environment Engineering and Research-Asia Pacific Division, IAHR-APD 2020: "Creating Resilience to Water-Related Challenges" 2020 
    Gabion revetments are often installed in front of beach scarps for short-term protection of the eroded beaches. Although the effect of a gabion revetment on direct sand protection is weaker than other impermeable costal structures, gabions induce natural recovery of a stable beach profile because of their permeability. This allows cross-shore sand transport while protecting the eroded beach if the gabions are installed at proper locations. The final goal of this research is to find out the optimum arrangement of beach-erosion countermeasures towards sustainable management of a beach profile. In this study, we will discuss the performance of round-shaped gabions as a material to form beach stabilization structures through laboratory experiments.
  • Takumi Nonaka, Yasunori Watanabe
    22nd Congress of the International Association for Hydro-Environment Engineering and Research-Asia Pacific Division, IAHR-APD 2020: "Creating Resilience to Water-Related Challenges" 2020 
    Surfactant concentration in seawater affects heat and gas exchanges between atmosphere and ocean via formations of air-bubbles during wave-breaking process as surfactant modifies surface tension to define bubble size. However, this effect to dynamics of bubble flows has poorly understood. This paper presents the surfactant effects on geometric and kinematic features of bubble plumes and residual surface foams observed in laboratory experiments using backlit image measurements. We found the both bubble size distributions in surfactant water and seawater are well approximated by a lognormal distribution, while the bubbles in pure water deviate from the distribution. We also found analogous features in mean diameter, population and terminal velocity of bubbles in the surfactant and sea waters. The behaviors of coalescence and collapse of buoyant residual foams on a still water surface highly depend on the surfactant concentration. Our findings may contribute to understand mechanical processes of aeration and degassing in regional and seasonal variations of surfactant concentration depending on oceanic biological activity.
  • A. Saruwatari, K. Fukuhara, Y. Watanabe
    Coastal Engineering Journal 61 (4) 520 - 534 2166-4250 2019/10/02 [Refereed][Not invited]
     
    © 2019, © 2019 Japan Society of Civil Engineers. Explosive cyclones formed in the northwest Pacific region can be categorized into three major types based on their evolution: Type-I cyclones develop over the Sea of Japan, Type-II are generated on the continent and move toward the Pacific Ocean, and Type-III travel northward in the Pacific Ocean along the Japanese archipelago. We performed computational experiments of past storm surges to find statistical features of local sea levels, depending on the types of the cyclone evolution under a realistic meteorological scenario of winter cyclones, with an aim to provide possible sea-level rise expected in the northeast Asia. Here, we show that amplification of local sea level, governed by the orientation of coastal lines with cyclone tracks, is defined by the evolution type that is classified by their trajectories, rather than the intensity, of the cyclone. Nemuro Bay is the most vulnerable site in the northwest Pacific region regardless of the evolution type. Severe storm surges are also expected along certain other semi-enclosed coasts facing the northern Sea of Japan and Sea of Okhotsk due to Type-I cyclones. The probabilistic evaluation of sea levels depending on the cyclone evolution type as introduced in this study may be useful for evaluating potential disasters.
  • SARUWATARI Ayumi, ISHIMI Shota, WATANABE Yasunori
    Journal of Japan Society of Civil Engineers, Ser. A2 (Applied Mechanics (AM)) 公益社団法人 土木学会 75 (2) I_531 - I_537 2185-4661 2019 [Refereed][Not invited]
     

    This study is to examine applicability of air-ion concentration to improve estimation accyracy of production rate of sea spray from the ocean. Concentration of air negative ions that is know to be influenced by generation of tiny sea spray was found to response to variation in production of film droplets induced by bubble bursting on water surface from our laboratory experiment. Also, concentration of air negative ions was observed in three ocean areas along Hokkaido, Japan; Sea of Japan, Sea of Okhotsk and the Pacific Ocean. The ion concentration was found to be correlated with the wind speed, wave height and whitecap ratio, all of which have been used as a model parameter of Sea Spray Generation Functions, indicating possibility of using air-ion concentration to accurate estimation of sea spray production.

  • 渡部靖憲, 杉村一直, 山下賢人, 猿渡亜由未
    土木学会論文集 B2(海岸工学)(Web) 土木学会 75 (2) I_49 - 54 1883-8944 2019 [Refereed][Not invited]
  • 高木雅史, 森信人, 二宮順一, 志村智也, 内山雄介, 馬場康之, 水谷英朗, 久保輝広, 渡部靖憲, 大塚淳一, 山田朋人, 猿渡亜由未
    土木学会論文集 B2(海岸工学)(Web) 土木学会 75 (2) I_61 - 66 1883-8944 2019 [Refereed][Not invited]
  • 猿渡亜由未, 大塚淳一, 馬場康之, 久保輝広, 水谷英朗, 志村智也, 二宮順一, 山田朋人, 内山雄介, 森信人, 渡部靖憲
    土木学会論文集 B2(海岸工学)(Web) 土木学会 75 (2) I_67 - 72 1883-8944 2019 [Refereed][Not invited]
  • 馬場 康之, 久保 輝広, 森 信人, 渡部 靖憲, 山田 朋人, 猿渡 亜由未, 大塚 淳一, 内山 雄介, 二宮 順一
    土木学会論文集. B2, 海岸工学 Journal of Japan Society of Civil Engineers. 土木学会海岸工学委員会 編 土木学会 75 (2) I_271 - 276 2019 [Refereed][Not invited]
  • 岡地寛季, 山田朋人, 渡部靖憲, 猿渡亜由未, 大塚淳一, 森信人, 馬場康之, 久保輝広, 二宮順一, 内山雄介, 水谷英郎
    土木学会論文集 G(環境)(Web) 土木学会 27 (5) 41 - 46 2185-6648 2019 [Refereed][Not invited]
  • Yuta Mitobe, Hitoshi Tanaka, Kazuya Watanabe, Neetu Tiwari, Yasunori Watanabe
    Coastal Engineering Journal 60 (4) 516 - 531 2166-4250 2018/10/02 [Refereed][Not invited]
     
    © 2018 of the Crown in Canada. National Research Council of Canada. In the 2011 Tohoku Earthquake Tsunami, run-up of the tsunami along rivers expanded the damaged area into more inland areas far from the coast. High water level in rivers was kept for more than several times of the wave period in the 2011 event, while more simple periodical oscillations of the water level superposed on the tidal motion was observed in the 2010 Chile Tsunami event. The difference of behaviors of tsunami in rivers was discussed with related to the magnitude of tsunami and river mouth morphology through two numerical experiments in this paper. In the first numerical experiments, the run-up of historical tsunamis was simulated along Kitakami River. It was found that the discharge of tsunami flow across the river mouth was proportional to third power of water depth if overflow of the sand spit occurred, and that caused unbalance of water volume coming into and going out from the river channel. Through the second numerical experiment with simple model bathymetry and sinusoidal waves, it was found that discharge during both tsunami run-up and run-down across river mouths is reduced by sand spits at the river mouths and the reduction effect is more significant during flow rushing into the rivers than that during return flow.
  • Yasuo Niida, Yasunori Watanabe
    Physics of Fluids 30 (10) 1070-6631 2018/10/01 [Refereed][Not invited]
     
    © 2018 Author(s). Air-bubble plumes produced beneath ocean breaking waves have important roles in gas transfer between atmosphere and ocean because the gas within the bubbles, convected by breaking-wave-induced turbulence, is dissolved at a deeper level. In particular, oxygen dissolution supports all biological activities in a marine ecosystem. Oxygen transfer from bubbles to bulk water depends on the dynamics of local bubble flows. As lateral bubble motion associated with vortex wakes generates turbulence in the ambient fluid, depending on the bubble size, the dissolved gas in the plume is transported via complex convection and diffusion processes. Although analytical and empirical models of gas transfer from a small, rigid bubble have been proposed previously, the effects of bubble size on gas concentrations in the turbulence field remain poorly understood. In this study, we examine the explicit effects of bubble size on bubble plume turbulence and the dissolved oxygen (DO) concentration field, and propose a new empirical gas transfer model that is applicable to large deformable bubbles on the basis of experimental imaging analysis. The gas transport process in the plume was identified using bubble turbulence coupled flow computations with the proposed gas source model, which well explained the variation in experimental DO concentration. The proposed transfer velocity model extended the applicable bubble size range and predicted the major features of the increasing oxygen concentration within the plume. We expect these findings to serve as a starting point to improve our understanding of the dynamics of practical bubble plume flows with wider bubble size ranges, as typically formed under breaking waves, and to predict oxygen concentrations in marine environments.
  • Hiroki Okachi, Tomohito J. Yamada, Yasunori Watanabe, Junichi Ohtsuka
    Proceedings - International Association for Hydro-Environment Engineering and Research (IAHR)-Asia Pacific Division (APD) Congress: Multi-Perspective Water for Sustainable Development, IAHR-APD 2018 1 493 - 502 2018/09/01 [Refereed][Not invited]
     
    © Proceeding of the 21st LAHR-APD Congress 2018. All rights reserved. Various fluxes are always exchanged at the air-sea surface. Considering flux exchanges in furious storm condition, there are much rain droplets and sea sprays generated from wave breaks. Sea sprays are instantly accelerated by local wind as they are generated. They have substantial mass. Therefore, momentum is conveyed by these droplets from the atmosphere to the ocean Focusing on the raindrops, they have horizontal speed more than wind speed when reaching the near-sea surface. That is, raindrops accelerate horizontal wind speed, however, there is no confirmation. Additionally, sea spray transfers latent heat extracted from the atmosphere in the process of its phase change. In this research, parameterization of momentum exchange at the air-sea surface is reconsidered concerning about drag coefficient. The drag coefficient increases as wind speed increases. We propose an equation which includes the effect of raindrops on the equation of drag coefficient that takes into account of sea spray and the characteristics of momentum exchange coefficient related to rainfall intensity and wind velocity. We also perform marine observation from 2013 to 2016 at an observational tower in Wakayama-prefecture, Japan, where typhoon often hits. Several typhoons passed near the tower for four years. We further conduct wind tunnel experiments to directly observe sea sprays (diameter > 72 μm) for six high wind speed conditions (U10=23∼28m/s).
  • 猿渡亜由未, 足立天翔, 宮武誠, 渡部靖憲
    土木学会論文集 B2(海岸工学)(Web) 74 (2) 1883-8944 2018
  • 門脇壮健, 渡部靖憲
    土木学会論文集 B2(海岸工学)(Web) 74 (2) 1883-8944 2018
  • 岡地寛季, 山田朋人, 渡部靖憲
    土木学会論文集 B1(水工学)(Web) 74 (4) 2185-467X 2018
  • 山下賢人, 渡部靖憲
    土木学会論文集 B2(海岸工学)(Web) 74 (2) 1883-8944 2018
  • Yasunori Watanabe, Yuta Mitobe, Hitoshi Tanaka, Kazuya Watanabe
    Proceedings of the Coastal Engineering Conference 36 (2018) 0161-3782 2018 [Refereed][Not invited]
  • Junichi Otsuka, Yasunori Watanabe
    Proceedings of the Coastal Engineering Conference 36 (2018) 0161-3782 2018 [Refereed][Not invited]
  • SARUWATARI Ayumi, ADACHI Amato, MIYATAKE Makoto, WATANABE Yasunori
    Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 公益社団法人 土木学会 74 (2) I_661 - I_666 1884-2399 2018 [Refereed][Not invited]
  • Turbulent Boundary Layer Flows over Progressive Water Waves
    K. Yamashita, Y. Watanabe, A. Saruwatari
    Proc. iCFM 2018 [Not refereed][Not invited]
  • Phase-Field computation of drop impacts
    S. Kadowaki, Y. Watanabe, A. Saruwatari
    Proc. iCFM 2018 [Not refereed][Not invited]
  • Ayumi Saruwatari, Junichi Otsuka, Yasunori Watanabe
    Proceedings of the Coastal Engineering Conference 36 (2018) 0161-3782 2018 [Refereed][Not invited]
  • 岡田 信瑛, 内山 雄介, 多田 拓晃, 遠藤 颯, 馬場 康之, 水谷 英朗, 久保 輝広, 森 信人, 渡部 靖憲, 大塚 淳一, 山田 朋人, 猿渡 亜由未, 二宮 順一
    土木学会論文集. B2, 海岸工学 Journal of Japan Society of Civil Engineers. 土木学会海岸工学委員会 編 土木学会 74 (2) I_667 - 672 1883-8944 2018 [Not refereed][Not invited]
  • 猿渡 亜由未, 坂川 諒太, 大塚 淳一, 馬場 康之, 久保 輝広, 水谷 英朗, 二宮 順一, 山田 朋人, 内山 雄介, 森 信人, 渡部 靖憲
    土木学会論文集. B2, 海岸工学 Journal of Japan Society of Civil Engineers. 土木学会海岸工学委員会 編 土木学会 74 (2) I_67 - 72 1883-8944 2018 [Not refereed][Not invited]
  • Mitobe Yuta, Tanaka Hitoshi, Watanabe Kazuya, Tiwari Neetu, Watanabe Yasunori
    COASTAL ENGINEERING JOURNAL 60 (4) 516 - 531 0578-5634 2018 [Refereed][Not invited]
  • Junichi Otsuka, Ayumi Saruwatari, Yasunori Watanabe
    Advances in Water Resources 110 59 - 76 0309-1708 2017/12 [Refereed][Not invited]
     
    © 2017 The Authors A major mechanism of sediment suspension by organized vortices produced under violent breaking waves in the surf zone was identified through physical and computational experiments. Counter-rotating flows within obliquely descending eddies produced between adjacent primary roller vortices induce transverse convergent near-bed flows, driving bed load transport to form regular patterns of transverse depositions. The deposited sediment is then rapidly ejected by upward carrier flows induced between the vortices. This mechanism of vortex-induced suspension is supported by experimental evidence that coherent sediment clouds are ejected where the obliquely descending eddies reach the sea bed after the breaking wave front has passed. In addition to the effects of settling and turbulent diffusion caused by breaking waves, the effect of the vortex-induced flows was incorporated into a suspension model on the basis of vorticity dynamics and parametric characteristics of transverse flows in breaking waves. The model proposed here reasonably predicts an exponential attenuation of the measured sediment concentration due to violent plunging waves and significantly improves the underprediction of the concentration produced by previous models.
  • Junichi Otsuka, Ayumi Saruwatari, Yasunori Watanabe
    ADVANCES IN WATER RESOURCES 110 59 - 76 0309-1708 2017/12 [Refereed][Not invited]
     
    A major mechanism of sediment suspension by organized vortices produced under violent breaking waves in the surf zone was identified through physical and computational experiments. Counter-rotating flows within obliquely descending eddies produced between adjacent primary roller vortices induce transverse convergent nearbed flows, driving bed load transport to form regular patterns of transverse depositions. The deposited sediment is then rapidly ejected by upward carrier flows induced between the vortices. This mechanism of vortex-induced suspension is supported by experimental evidence that coherent sediment clouds are ejected where the obliquely descending eddies reach the sea bed after the breaking wave front has passed. In addition to the effects of settling and turbulent diffusion caused by breaking waves, the effect of the vortex-induced flows was incorporated into a suspension model on the basis of vorticity dynamics and parametric characteristics of transverse flows in breaking waves. The model proposed here reasonably predicts an exponential attenuation of the measured sediment concentration due to violent plunging waves and significantly improves the underprediction of the concentration produced by previous models.
  • 南翔, 工藤圭太, 八木澤一城, 橋本孝治, 渡部靖憲
    土木学会論文集 B2(海岸工学)(Web) 73 (2) 1883-8944 2017
  • 木岡信治, 遠藤強, 竹内貴弘, 渡部靖憲
    土木学会論文集 B2(海岸工学)(Web) 73 (2) 1883-8944 2017
  • 渡部靖憲, 杉村一直
    土木学会論文集 B2(海岸工学)(Web) 73 (2) 1883-8944 2017
  • 渡部靖憲, 鈴木敦貴
    土木学会論文集 B2(海岸工学)(Web) 73 (2) 1883-8944 2017
  • 水戸佳祐, 八木澤一城, 佐野朝昭, 橋本孝治, 本田達也, 本山賢司, 渡部靖憲
    土木学会論文集 B2(海岸工学)(Web) 73 (2) 1883-8944 2017
  • 吉田 徹, 橋本 茂樹, 時沢 武史, 小田 玲司, 猿渡 亜由未, 渡部 靖憲
    寒地技術論文・報告集 寒地技術シンポジウム 北海道開発技術センター 33 229 - 234 1883-3489 2017 [Not refereed][Not invited]
  • KIOKA Shinji, ENDO Tsutomu, TAKEUCHI Takahiro, WATANABE Yasunori
    Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 公益社団法人 土木学会 73 (2) I_973 - I_978 1884-2399 2017 [Refereed][Not invited]
     
     Medium-scale experiments and numerical calculations by DEM were performed to examine the dynamic fracture of sea ice masses by their collisions with prismatic structures along with a flat plane and to propose a simple method to estimate the collision force. It was confirmed that the actual collision under ideal conditions such as complete surface to surface contact by ice with uniform material properties would be very rare, and that the experimental results were consequently scattered. The maximum collision forces by the numerical calculations agreed with a theoretical simple formula for a flat-plane structure whether ice fracture occurred or not. We proposed a simple method to estimate the forces with structures with arbitrary size base on the theoretical formula and the experimental results including DEM/FEM.
  • WATANABE Yasunori, SUGIMURA Kazunao
    Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 公益社団法人 土木学会 73 (2) I_73 - I_78 1884-2399 2017 [Refereed][Not invited]
     
     This paper presents mechanical features of transitional air-water momentum and energy transfers in initial growing wind waves on the basis of the fluid flow statistics observed in wind-wave tunnel experiments. In the initial waves with short fetch, superpositions of capillary waves on the crest of gravity waves generate significant vorticity and transport it downward, resulting in a thick momentum boundary layer containing organized vortices. As the capillaries attenuate in growing wind-driven current via wave-current interaction, with increase of fetch, vorticity generation also attenuate and thus the thickness of the boundary layer decrease.
  • MIZUTO Keisuke, YAGISAWA Kazuki, SANO Tomoaki, HASHIMOTO Koji, HONDA Tatsuya, MOTOYAMA Kenji, WATANABE Yasunori
    Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 公益社団法人 土木学会 73 (2) I_829 - I_834 1884-2399 2017 [Refereed][Not invited]
     
     Tomamae fishing port is hindered the use of port areas and boat moorings behind the western outskirts by the overtopping waves, especially in winter season. However, in this port, comprehensive viewpoints including the formation of overtopping waves and environmental conditions which generate wave overtopping have not been revealed yet. In this study, in order to understand the wave overtopping in the western outskirts, field observation using a web camera was conducted, and various analyzes were made on the relationship between the overtopping wave phenomenon captured by the web camera and environmental conditions, including wave, wind and tidal level. Furthermore, conducting numerical simulation with CADMAS-SURF, on-site characteristics on wave overtopping were revealed.
  • MINAMI Sho, KUDOU Keita, YAGISAWA Kazuki, HASHIMOTO Koji, WATANABE Yasunori
    Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 公益社団法人 土木学会 73 (2) I_205 - I_210 1884-2399 2017 [Refereed][Not invited]
     
     Typhoon Lionlock (2016) followed a complicated route that was different from the conventional typhoon. Lionlock moved northwest of the Tohoku region, and proceeded to the Sea of Japan . the typhoon caused large fishery damage due to windward flow and strong winds in Hokkaido's Uchura Bay.it is very important to calcurate tide deviation occured by typhoon that followed a characteristic course. Therefore, in this study, numerical experiments using a typhoon model and nonlinear longwave model were performed. Using the Lionlock typhoon as a model, we calculated the storm surge of eight possible tracks, clarified the occurrence characteristics of the tide deviation in Uchiura Bay and estimated the damages along each track. Further, we made calculations for creating a tidal flooded immersion area map (Ministry of Land, Infrastructure and Transport), and obtained knowledge on measures to use against storm surges along the coast of Uchiura Bay in the future.
  • WATANABE Yasunori, SUZUKI Atsuki
    Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 公益社団法人 土木学会 73 (2) I_91 - I_96 1884-2399 2017 [Refereed][Not invited]
     
     A novel experiment of free-surface deformation in a rotating circular cylinder is proposed in this study, which physically models an air-tube fragment observed in a plunging wave breaking. It is found during the experiment that the fragment is induced by unstable anti-symmetric rotating flows around air-tube affected by centrifugal force, surface tension, buoyancy and drag force. Overall features of the fragment wave-number and critical rotation frequency can be described in terms of Froude and Weber numbers.
  • A new approach to numerical modeling of tsunami considering unsteady boundary layer develpment
    Hitoshi Tanaka, Yuta Mitobe, Neetu Tiwari, Kazuya Watanabe, Yasunori Watanabe
    Proceedings of The 3rd International Conference on Coastal Zone Engineering and Management in the Middle East (Arabian Coast 2016) (Nov 20-23, Debai UAE) (Keynote lecture) 2016/11/22 [Refereed][Invited]
  • Yasunori Watanabe, Hitoshi Tanaka, Yuta Mitobe, Kazuya Watanabe
    Journal of JSCE B2 (Coastal Eng) B2-72 (2) I_283 - I_288 1883-8944 2016/11/17 [Refereed][Not invited]
  • Yuta Mitobe, Kazuya Watanabe, Hitoshi Tanaka, Neetu Tiwari, Yasunori Watanabe
    Journal of JSCE B2 (Coastal Eng) B2-72 (2) I_259 - I_264 1883-8944 2016/11/17 [Refereed][Not invited]
  • 内山 雄介, 吉木 智軌, 多田 拓晃, 馬場 康之, 水谷, 久保 輝広, 森 信人, 猿渡 亜由未, 大塚 淳一, 二宮 順一, 渡部 靖憲, 山田 朋人
    土木学会論文集B4(海岸工学) = Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 土木学会 = Japan Society of Civil Engineers 72 (2) I_493 - I_498 1884-2399 2016/11/15 [Refereed][Not invited]
     
    For rigorious description of upper ocean dynamics and resultant volume transport at the mouth of Tanabe Bay, Wakayama, Japan, a comprehensive field campaign was conducted from summer to fall of 2015. The vertical structure of transient dynamics in the surface boundary layer and consequent water exchange at the mouth are characterized by high-frequency variability peaked at around the semi-diurnal period as well as in the lower-frequency subtidal band centered at 3 day period, consistent with the previous modeling study. A spectral coherence analysis indicates that near-surface currents are mainly driven by wind stress peaked at the diurnal frequency, whereas subsurface currents fluctuate rather by semi-diurnal internal tides. The upper ocean cools down gradually, corresponding to seasonal transition from summer to fall condition. However, an abrupt cooling event is observed albeit in a calm local forcing condition where an offshore subtidal cold water intrusion induced remotely by the fluctuating Kuroshio path plays an essential role.
  • 久保 慎也, 二宮 順一, 森 信人, 馬場 康之, 水谷 英朗, 久保 輝広, 内山 雄介, 渡部 靖憲, 山田 朋人, 大塚 淳一, 猿渡 亜由未
    土木学会論文集B2(海岸工学) = Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 土木学会 = Japan Society of Civil Engineers 72 (2) I_487 - I_492 1884-2399 2016/11/15 [Refereed][Not invited]
     
    This study focuses on the process of thermocline's destruction and reformation during typhoons using field observation data. The thermocline has a large effect on the circulation and would be a factor to make water worse. Therefore, it is necessary to understand its process deeply. In this study, the stability of density stratification was evaluated based on the Brant-Vaisala frequency and the Richardson number. The results suggested that high wave destroyed the stratification and high wind mixed ocean water vertically more energetically during stratified season. On the other hand, is was found that stratification was unstable regardless of typhoon intensity during unstratified season. Moreover, the characteristics of water-mass were evaluated on the TS diagram during unstratified season.
  • Yuta Mitobe, Neetu Tiwari, Kazuya Watanabe, Hitoshi Tanaka, Yasunori Watanabe
    Journal of JSCE B2 (Coastal Eng) B2-72 (2) I_259 - I_264 1883-8944 2016/11 [Refereed][Not invited]
  • Y. Watanabe, D. M. Ingram
    Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 472 (2194) 20160423  1364-5021 2016/10/01 [Refereed][Not invited]
     
    © 2016 The Author(s) Published by the Royal Society. All rights reserved. When a steep, breaking wave hits a vertical sea wall in shallow water, a flip-through event may occur, leading to the formation of an up-rushing planar jet. During such an event, a jet of water is ejected at a speed many times larger than the approaching wave's celerity. As the jet rises, the bounded fluid sheet ruptures to form vertical ligaments which subsequently break up to form droplets, creating a polydisperse spray. Experiments in the University of Hokkaido's 24 m flume measured the resulting droplet sizes using image analysis of high-speed video. Consideration of the mechanisms forming spray droplets shows that the number density of droplet sizes is directly proportional to a power p of the droplet radius: where p =-5/2 during the early break-up stage and p =-2 for the fully fragmented state. This was confirmed by experimental observations. Here, we show that the recorded droplet number density follows the lognormal probability distribution with parameters related to the elapsed time since the initial wave impact. This statistical model of polydisperse spray may provide a basis for modelling droplet advection during wave overtopping events, allowing atmospheric processes leading to enhanced fluxes of mass, moisture, heat and momentum in the spraymediated marine boundary layer over coasts to be described.
  • Jonathan M. Nelson, Yasuyuki Shimizu, Takaaki Abe, Kazutake Asahi, Mineyuki Gamou, Takuya Inoue, Toshiki Iwasaki, Takaharu Kakinuma, Satomi Kawamura, Ichiro Kimura, Tomoko Kyuka, Richard R. McDonald, Mohamed Nabi, Makoto Nakatsugawa, Francisco R. Simões, Hiroshi Takebayashi, Yasunori Watanabe
    Advances in Water Resources 93 62 - 74 0309-1708 2016/07/01 [Refereed][Not invited]
     
    © 2015 This paper describes a new, public-domain interface for modeling flow, sediment transport and morphodynamics in rivers and other geophysical flows. The interface is named after the International River Interface Cooperative (iRIC), the group that constructed the interface and many of the current solvers included in iRIC. The interface is entirely free to any user and currently houses thirteen models ranging from simple one-dimensional models through three-dimensional large-eddy simulation models. Solvers are only loosely coupled to the interface so it is straightforward to modify existing solvers or to introduce other solvers into the system. Six of the most widely-used solvers are described in detail including example calculations to serve as an aid for users choosing what approach might be most appropriate for their own applications. The example calculations range from practical computations of bed evolution in natural rivers to highly detailed predictions of the development of small-scale bedforms on an initially flat bed. The remaining solvers are also briefly described. Although the focus of most solvers is coupled flow and morphodynamics, several of the solvers are also specifically aimed at providing flood inundation predictions over large spatial domains. Potential users can download the application, solvers, manuals, and educational materials including detailed tutorials at www.-i-ric.org. The iRIC development group encourages scientists and engineers to use the tool and to consider adding their own methods to the iRIC suite of tools.
  • KIOKA Shinji, TAKEUCHI Takahiro, WATANABE Yasunori
    Proceedings of the International Symposium on Okhotsk Sea & Sea Ice 31st 270‐273  2016/02/20 [Not refereed][Not invited]
  • 大塚淳一, 渡部靖憲
    土木学会論文集 B2(海岸工学)(Web) 72 (2) 1883-8944 2016
  • 小柳津遥陽, 渡部靖憲
    土木学会論文集 B2(海岸工学)(Web) 72 (2) 1883-8944 2016
  • 渡部靖憲, 佐々木理沙, 小柳津遥陽, 牧田拓也, 森岡晃一, 猿渡亜由未
    土木学会論文集 B2(海岸工学)(Web) 72 (2) 1883-8944 2016
  • 内山雄介, 吉木智軌, 多田拓晃, 馬場康之, 水谷英朗, 久保輝広, 森信人, 猿渡亜由未, 大塚淳一, 二宮順一, 渡部靖憲, 山田朋人
    土木学会論文集 B2(海岸工学)(Web) 72 (2) 1883-8944 2016
  • 久保慎也, 二宮順一, 森信人, 馬場康之, 水谷英朗, 久保輝広, 内山雄介, 渡部靖憲, 山田朋人, 大塚淳一, 猿渡亜由未
    土木学会論文集 B2(海岸工学)(Web) 72 (2) 1883-8944 2016
  • 木岡信治, 遠藤強, 竹内貴弘, 渡部靖憲
    土木学会論文集 B2(海岸工学)(Web) 72 (2) 1883-8944 2016
  • SARUWATARI Ayumi, TAKEE Toshihiro, WATANABE Yasunori
    Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 公益社団法人 土木学会 72 (2) I_247 - I_252 1883-8944 2016 [Refereed][Not invited]
     
     Explosively developing extratropical cyclones are becoming one of the important factors to cause a storm surge in winter. This study statistically evaluates risk of storm surge based on 3D flow fields under developing storm surge computed for various meteorological conditions. Vertical structure of the flow in the Nemuro Bay driven by the strong wind and wind-induced surface gradient showed characteristics different from that in the open ocean forming a typical Ekman spiral. Surge height and event duration are sensitive to the cyclone trajectory. The results of this study also shows the highest surge level in the Nemuro Bay had a risk to increase more than 1.5 times as high as the highest surge of the storm event in 2014.
  • SARUWATARI Ayumi, NINOMIYA Junichi, WATANABE Yasunori, YAMADA Tomohito, OTSUKA Junichi, BABA Yasuyuki, MIZUTANI Hideaki, KUBO Teruhiro, UCHIYAMA Yusuke, MORI Nobuhito
    Journal of Japan Society of Civil Engineers, Ser. A2 (Applied Mechanics (AM)) 公益社団法人 土木学会 72 (2) I_537 - I_547 2185-4661 2016 [Refereed][Not invited]
     
    Sea spray is one of the important factors to affect weather conditions over the ocean in terms of constituting an aerosol as well as determining air-sea transport of heat, moisture and momentum. The final goal of this study is to explain the relationship between sea-spray generation and conditions of the atmosphere and ocean for a more accurate prediction of the amount of sea spray. This study conducted three-year field observations of atmospheric aerosol at an offshore observatory in Tanabe Bay, Wakayama. Large-scale (> 100 km) distribution of atmospheric aerosol was found to dominate the concentration of the observed aerosol less than 1 μm in normal weather conditions. During storm events with strong winds from the Pacific Ocean, however, the observed concentration monotonically increased with the wind speed, which is considered to be a result of the increase in oceanic aerosol derived from sea spray.
  • WATANABE Yasunori, SASAKI Risa, OYAIZU Haruhi, MAKITA Takuya, MORIOKA Koichi, SARUWATARI Ayumi
    Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 公益社団法人 土木学会 72 (2) I_67 - I_72 1884-2399 2016 [Refereed][Not invited]
     
     This paper presents the boundary condition model, based on empirical contact angle model, for free-surfaces on moving contact lines of run-up waves. The inundation process on an urban topographic model composed of streets and impermeable blocks, which models urban floods observed in Kamaishi city affected by the 2011 Tohoku tsunami, was computed in this study. We find unsteady bores are consecutively formed under steady overflows from a tide wall and propagate along streets, which causes unsteady wave forces on urban buildings for long time.
  • 猿渡亜由未, 渡部靖憲
    土木学会論文集 B2(海岸工学)(Web) 71 (2) 1537 - 1542 1883-8944 2015/11 [Refereed][Not invited]
  • Y. Watanabe, D. M. Ingram
    Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 471 (2182) 1364-5021 2015/10/08 [Refereed][Not invited]
     
    © 2015 The Author(s) Published by the Royal Society. All rights reserved. When a steep breaking wave hits a vertical sea wall, in shallow water, a rapidly ascending planar jet forms. This jet is ejected with high acceleration due to pressure created by the violent wave impact on the wall, creating a so-called 'flip-through' event. Previous studies have focused on the impulsive pressures on, and within, the wall and on the velocity of the jet. Here, in contrast, we consider the formation and break-up of the jet itself. Experiments show that during flip-through a fluid sheet, bounded by a rim, forms. This sheet has unstable transitional behaviours and organizing jets; undulations in the thickness of the fluid sheet are rapidly amplified and ruptured into an array of vertical ligaments. Lateral undulations of the rim lead to the formation of fingerjets, which subsequently break up to form droplets and spray. We present a linear stability analysis of the rim-sheet systems that highlights the contributions of rim retraction and sheet stretching to the breakup process. The mechanisms for the sequential surface deformations in the rim-sheet system are also described. Multiple, distinct, instability modes are identified during the rim deceleration, sheet stretch attenuation and rim retraction processes. The wavenumbers (and deformation length scales) associated with these instability modes are shown to lead to the characteristic double peak spectrum of surface displacement observed in the experiments. These mechanisms help to explain the columnar structures often seen in photographs of violent wave impacts on harbour walls.
  • Ayumi Saruwatari, Adriano Coutinho De Lima, Masaya Kato, Osamu Nikawa, Yasunori Watanabe
    Coastal Engineering Journal 57 (3) 2166-4250 2015/09/19 [Refereed][Not invited]
     
    © 2015 World Scientific Publishing Company and Japan Society of Civil Engineers. From Tuesday, 16 December 2014, until Thursday, 18 December 2014, Hokkaido was battered by strong winds and high sea waves caused by a passing low pressure system intensified to typhoon levels. In the city of Nemuro, a rise in sea level influenced by the storm surge which exceeded quay height in port areas was observed from predawn Wednesday, 17 December 2014. Flooding was experienced in areas of central Nemuro, the Nemuro Port and estuaries of rivers. This technical note provides a comprehensive meteorological analysis and the results of a local flood survey carried out by the authors from 19 to 21 December 2014, and summarizes the characteristics of the 2014 Nemuro storm surge disaster.
  • Ayumi Saruwatari, Adriano Coutinho de Lima, Masaya Kato, Osamu Nikawa, Yasunori Watanabe
    COASTAL ENGINEERING JOURNAL 57 (3) 1550014.1-1550014.14  0578-5634 2015/09 [Refereed][Not invited]
     
    From Tuesday, 16 December 2014, until Thursday, 18 December 2014, Hokkaido was battered by strong winds and high sea waves caused by a passing low pressure system intensified to typhoon levels. In the city of Nemuro, a rise in sea level influenced by the storm surge which exceeded quay height in port areas was observed from predawn Wednesday, 17 December 2014. Flooding was experienced in areas of central Nemuro, the Nemuro Port and estuaries of rivers. This technical note provides a comprehensive meteorological analysis and the results of a local flood survey carried out by the authors from 19 to 21 December 2014, and summarizes the characteristics of the 2014 Nemuro storm surge disaster.
  • Junichi Otsuka, Yasunori Watanabe
    Coastal Engineering Journal 57 (2) 2166-4250 2015/06/20 [Refereed][Not invited]
     
    © 2015 World Scientific Publishing Company and Japan Society of Civil Engineers. An ultrasonic velocity profiler (UVP) acquires instantaneous distributions of axial velocity along the ultrasonic beam emitted from the transducer. In this paper, organizations of the transverse flows over a span of a laboratory wave flume in the surf zone were identified experimentally on the basis of UVP measurements. Ensemble mean divergent and convergent flows were observed over the span of the flume in the surf zone regardless of breaker conditions. By analogy with the flow evolution in a previous computation, by Watanabe and Saeki [1999], we identified that the organization of the wave-breaking-induced counter-rotating vortices determined the spatial and temporal variations in the transverse flows at the early stages of the breaking process regardless of the widths of wave flumes and friction on the sidewalls and bottom. The observed transverse flows were driven by pairs of counter-rotating vortices produced under the breaking waves and the change in the orientation during the passage of breaking waves. The fundamental features of the transverse flows evolving in the breaking process, depending on the breaker type, are discussed statistically to parameterize velocity, time, and length scales of the variations of the transverse velocity. The dimensionless length and time scales had negative linear correlations with the Froude number (defined by relative transverse convection with respect to gravity) as well as a surf similarity parameter, which indicates that the gravity effect associated with the projections of the breaking wave crests defines the primary roller vorticity and shear intensity at the plunging location, resulting in destabilization of the flows in the transverse direction to form organized transverse flow structures.
  • Junichi Otsuka, Yasunori Watanabe
    COASTAL ENGINEERING JOURNAL 57 (2) 1550006.1-1550006.22  0578-5634 2015/06 [Refereed][Not invited]
     
    An ultrasonic velocity profiler (UVP) acquires instantaneous distributions of axial velocity along the ultrasonic beam emitted from the transducer. In this paper, organizations of the transverse flows over a span of a laboratory wave flume in the surf zone were identified experimentally on the basis of UVP measurements. Ensemble mean divergent and convergent flows were observed over the span of the flume in the surf zone regardless of breaker conditions. By analogy with the flow evolution in a previous computation, by Watanabe and Saeki [1999], we identified that the organization of the wave-breaking-induced counterrotating vortices determined the spatial and temporal variations in the transverse flows at the early stages of the breaking process regardless of the widths of wave flumes and friction on the sidewalls and bottom. The observed transverse flows were driven by pairs of counter-rotating vortices produced under the breaking waves and the change in the orientation during the passage of breaking waves. The fundamental features of the transverse flows evolving in the breaking process, depending on the breaker type, are discussed statistically to parameterize velocity, time, and length scales of the variations of the transverse velocity. The dimensionless length and time scales had negative linear correlations with the Froude number (defined by relative transverse convection with respect to gravity) as well as a surf similarity parameter, which indicates that the gravity effect associated with the projections of the breaking wave crests defines the primary roller vorticity and shear intensity at the plunging location, resulting in destabilization of the flows in the transverse direction to form organized transverse flow structures.
  • WATANABE Yasunori, OSHIMA Yuki
    PROCEEDINGS OF THE JAPANESE CONFERENCE ON COASTAL ENGINEERING Japan Society of Civil Engineers 71 (2) I_43 - I_48 1884-2399 2015 
    In this study, imaging experiments for measuring free-surface shapes of run-up dambreak waves and fluid velocity distributions on the basis of Laser-Induced Fluorescence (LIF) and Super-Resolution Particle Imaging Velocimetry (SRPIV) were performed with aim to identify kinetic features of the run-up flows depending on slop angles. Organized patterns of the rotational shear flows are found to be formed in the bottom and surface boundary layers behind the wave front, which provides mechanical effects to provide typical blob-like surface shape in the wave front as well as wavy surface form behind it.
  • WATANABE Yasunori, MAKITA Takuya, OYAIZU Haruhi
    PROCEEDINGS OF THE JAPANESE CONFERENCE ON COASTAL ENGINEERING Japan Society of Civil Engineers 71 (2) I_37 - I_42 1884-2399 2015 
    In this study, local behaviors of cavities formed at impact of a steady planar jet onto still water were measured on the basis of a high-speed, high-resolution back-light imaging technique. The characteristic time and length scales to define deformation of the cavities, depending on the impact velocity, were analyzed to identify the mechanisms of the cavity growth. The both capillary and vortex-induced pressure are found to govern the local cavity behaviors.
  • KIOKA Shinji, ENDO Tsutomu, TAKEUCHI Takahiro, WATANABE Yasunori
    PROCEEDINGS OF THE JAPANESE CONFERENCE ON COASTAL ENGINEERING Japan Society of Civil Engineers 71 (2) I_919 - I_924 1884-2399 2015 
    We performed model experiments to clarify the increased risks caused by sea ice floes driven by runup tsunami against a structure with piloti column construction, which has been applied to a tsunami evacuation facility. After the collision force imparted by the ice floes acts on the columns, the run-up flow is dammed by the formation of ice jams and ice pile-ups between the columns, and a large static force in the main flow direction. The force is one order of magnitude greater than that in case without ice floes, also acts on the structure because of the water level rise and the ice pile-ups in front of the structure and because of hydrostatic pressure between the columns due to the ice-jam, and this steady state remains for some time. A large force in the vertical direction also acts on the structure, which is the same level as that in the main flow direction. We suggested that, in designing of structures with openings, such as windows and space between columns, the design force for tsunami flow acting on such parts should not be reduced because of the formation of the ice jams and pile-ups. We also suggested that we should evacuate to higher places than usual, because of the water level rise and the ice pile-ups.
  • 渡部靖憲, 牧田拓也, 小柳津遥陽
    土木学会論文集 B2(海岸工学)(Web) 71 (2) 1883-8944 2015
  • 渡部靖憲, 大島悠揮
    土木学会論文集 B2(海岸工学)(Web) 71 (2) 1883-8944 2015
  • 井上卓也, 長谷川和義, 渡部靖憲, 船木淳悟
    土木学会論文集 A2(応用力学)(Web) 71 (2) 2185-4661 2015
  • 一瀬輪子, 北野慈和, 山田朋人, 渡部靖憲, 泉典洋
    土木学会論文集 G(環境)(Web) 71 (5) 2185-6648 2015
  • 木岡信治, 遠藤強, 竹内貴弘, 渡部靖憲
    土木学会論文集 B2(海岸工学)(Web) 71 (2) 1883-8944 2015
  • Shinji Kioka, Takahiro Takeuchi, Yasunori Watanabe
    Proceedings of the International Offshore and Polar Engineering Conference 2015-January 778 - 782 1098-6189 2015 [Refereed][Not invited]
     
    Copyright © 2015 by the International Society of Offshore and Polar Engineers (ISOPE). We performed model experiments on the inundation flow of tsunamis with ice floes. After the collision force imparted by the ice floes acts on structures, the tsunami flow is dammed by the formation of ice jams between the structures, and a large static force also acts on the structures because of the water level rise in front of the structures and because of hydrostatic pressure between the structures due to the ice-jam, and this steady state remains for some time. We developed a simple theoretical model for estimating the water depth and the tsunami force, and we verified the validity of the model.
  • 内山 雄介, 松川 大佑, 神吉 亮佑, 馬場 康之, 森 信人, 水谷 英朗, 渡部 靖憲, 大塚 淳一, 山田 朋人, 猿渡 亜由未, 二宮 順一
    土木学会論文集B2(海岸工学) = Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 公益社団法人 土木学会 70 (2) I_446 - I_450 1884-2399 2014/11 [Not refereed][Not invited]
     
    Tanabe bay is a small embayment connected directly to the Pacific Ocean to the south, whereas frequently suffers from harmful algal blooms due to sewage effluent and the local aquaculture industry. For preserving the ecosystem in the bay, it is necessary to understand an oceanic structure in the bay along with water exchange at the bay entrance. We thus conduct a comprehensive investigation consisting of a shipboard measurement, a season-long platform observation, and a triply nested high-resolution ocean modeling. The water exchange at the bay mouth is largely affected by semi-diurnal tidal currents and episodic subtidal intrusion of the offshore water controlled by mesoscale circulations.
  • 和田 萌実, 泉 典洋, 渡部 靖憲
    水工学論文集 土木学会水工学委員会 編 土木学会 58 (70) 1177 - 1182 1880-8751 2014/02 [Not refereed][Not invited]
  • WATANABE Yasunori, OSHIMA Yuki
    PROCEEDINGS OF THE JAPANESE CONFERENCE ON COASTAL ENGINEERING Japan Society of Civil Engineers 70 (2) I_186 - I_190 1884-2399 2014 
    Imaging measurements of runup dam-break waves over sloping beds were performed for identifying kinematic features of wave propagation and free-surface transition. It has been found that typical blob like front shapes with transverse undulations were developed during propagation especially on highly sloping beds. The rolling motion of the wave front at the bed contact was observed to entrain air beneath the water layer behind the front, which becomes mechanically unstable to be fragmented into bubbles and to affect the wave forms.
  • KIOKA Shinji, MORI Masaya, ENDO Tsutomu, TAKEUCHI Takahiro, WATANABE Yasunori
    PROCEEDINGS OF THE JAPANESE CONFERENCE ON COASTAL ENGINEERING Japan Society of Civil Engineers 70 (2) I_821 - I_825 1884-2399 2014 
    We made model experiments on run-up tsunami inunduation flow with sea ice floes in an urban area. After the collision force of ice acts on structures, flow is dammed up due to the formation of Ice-jam between the structures, and large static force also acts on the structures because of water level rise and water pressure between the structures due to the jamming. The steady state is kept for a while. While we developed a simple mechanical model for estimation of the water depth and the tsunami force at the steady state, we compared calculated values by this model with experimental ones to verify the validity of the model. Further, in the design of facilities with openings such as windows and pilotis, we proposed that the design force by tsunami current acting on such parts should not be reduced because of the jamming.
  • NIIDA Yasuo, WATANABE Yasunori
    PROCEEDINGS OF THE JAPANESE CONFERENCE ON COASTAL ENGINEERING Japan Society of Civil Engineers 70 (2) I_51 - I_55 1884-2399 2014 
    This paper proposed an oxygen transfer model for bubble-laden turbulence generated by plunging jets. The proposing model has been validated through comparisons with experiments for bubble velocity, liquid velocity, liquid turbulence and oxygen flux. It was found dissolved oxygen concentrations in bubbly flows was determined by local bubble behaviors and turbulent flows modified around bubbles. This bubble-mediated gas transfer via mechanical interaction between bubbles and turbulence is important to understand air-sea gas exchange in the surf zone.
  • WATANABE Yasunori, OYAIZU Haruhi, NIIDA Yasuo
    PROCEEDINGS OF THE JAPANESE CONFERENCE ON COASTAL ENGINEERING Japan Society of Civil Engineers 70 (2) I_61 - I_65 1884-2399 2014 
    This paper presents a novel stochastic-LES hybrid model for favre averaged bubble-turbulence interactions in free-surface flows. The current model is found to be capable of computing local behaviors of dense bubble flows coupled with fluid turbulent motion, which is ensured by comparisons with experimental observations. The model is also applied to the flow at a planar jet impact onto a still water, as a model of overturning jets of breaking waves, which reasonably computed cavity deformation, air tube entrainment and bubble formations.
  • 内山雄介, 松川大佑, 神吉亮佑, 馬場康之, 森信人, 水谷英朗, 渡部靖憲, 大塚淳一, 山田朋人, 猿渡亜由未, 二宮順一
    土木学会論文集 B2(海岸工学)(Web) 70 (2) 1883-8944 2014
  • 渡部靖憲, 小柳津遥陽, 新井田靖郎
    土木学会論文集 B2(海岸工学)(Web) 70 (2) 1883-8944 2014
  • 新井田靖郎, 渡部靖憲
    土木学会論文集 B2(海岸工学)(Web) 70 (2) 1883-8944 2014
  • 渡部靖憲, 大島悠揮
    土木学会論文集 B2(海岸工学)(Web) 70 (2) 1883-8944 2014
  • 馬場康之, 水谷英朗, 久保輝広, 内山雄介, 森信人, 渡部靖憲, 大塚淳一, 山田朋人, 猿渡亜由未, 二宮順一
    土木学会論文集 B2(海岸工学)(Web) 70 (2) 1883-8944 2014
  • 和田萌実, 泉典洋, 渡部靖憲
    土木学会論文集 B1(水工学)(Web) 70 (4) 2185-467X 2014
  • 木岡信治, 森昌也, 遠藤強, 竹内貴弘, 渡部靖憲
    土木学会論文集 B2(海岸工学)(Web) 70 (2) 1883-8944 2014
  • 小窪一毅, 中山恵介, 新谷哲也, 大塚淳一, 渡部靖憲, 柿沼太郎, 駒井克昭, 清水健司
    土木学会論文集 B3(海洋開発)(Web) 70 (2) I.193-I.198 (J-STAGE)  2185-4688 2014 [Refereed][Not invited]
  • 小窪一毅, 中山恵介, 新谷哲也, 大塚淳一, 渡部靖憲, 柿沼太郎, 駒井克昭, 清水健司
    土木学会論文集 B1(水工学)(Web) Japan Society of Civil Engineers 70 (4) I.1195-I.1200 (J-STAGE) - I_1200 2185-467X 2014 [Refereed][Not invited]
     
    This study describes a horizontal circulation induced by the breaking of internal Kelvin waves over a uniform slope. In lakes or coastal regions, wind stress over a water surface or tide at the bay mouth may induce internal waves, which deform as internal Kelvin waves when the inertia radius is equal or less than the spatial scale of a lake or a bay. In general, internal Kelvin waves break due to the topographical features, such as a slope, which is revealed to cause horizontal circulation in the upper layer. The previous studies demonstrated that a horizontal circulation is induced due to the secondary lateral current due to the breaking of internal Kelvin waves over a slope. However, the development and damping of the horizontal circulation have not been clarified. Therefore, this study aims to investigate the occurrence of a horizontal circulation due to the internal Kelvin wave breaking over a slope by using laboratory experiments and numerical computations.
  • Nobuhito Mori, Tomoyuki Takahashi, Shun Etsu Hamaura, Kazuya Miyakawa, Katsuhiko Tanabe, Keisuke Tanaka, Mitsuyuki Tanaka, Tsukasa Watanabe, Hideo Matsutomi, Kazunori Naoe, Takuya Noumi, Erika Yamaguchi, Shoichi Ando, Yushiro Fujii, Toshihide Kashima, Yasuo Okuda, Bun'ichiro Shibazaki, Tsutomu Sakakiyama, Masafumi Matsuyama, Takumi Yoshii, Kazuhisa Goto, Takashi Aida, Yuuji Kurata, Mabumi Miyazaki, Katuya Shutou, Jun Suzuki, Hikari Takeuchi, Takayuki Nakamura, Osamu Fujiwara, Kyoko Kagohara, Haruo Kimura, Junko Komatsubara, Yukari Miyashita, Yuichi Namegaya, Yuki Sawai, Masanobu Shishikura, Koichiro Tanigawa, Hermann Fritz, Ken Ichi Uzaki, Mikio Sasaki, Masato Minami, Hitoshi Endou, Masaki Hashimoto, Yutaka Kobashigawa, Masamitsu Kumagai, Masahiro Ietsune, Kazuhiko Nakamura, Aditya Gusman, Kazuomi Hirakawa, Kei Loki, Yugo Nakamura, Takafumi Nakayama, Yuichi Nishimura, Puma Putra, Ayumi Saruwatari, Yasunori Watanabe, Tomohito Yamada, Yasunori Nabetani, Hisamichi Nobuoka, Takashi Tamada, Yuriko Matsubayashi, Toshinori Ogasawara, Shigeki Sakai, Masao Abe, Yutaka Hayashi, Hideki Iino, Kazuhiro Iwakiri, Kazuhiro Kimura, Kenji Maeda, Masami Okada, Hiroaki Tsushima, Taro Kakinuma, Kei Yamashita, Shinya Umeda, Takahiro Nakamura, Shuji Seto, Kurokawa Takahiro, Tetsuya Torayashiki, Gozo Tsujimoto, Kohji Uno, Shoichi Yoshioka, Norio Dewa, Tetsuya Hayashi, Mitsuyoshi Kitamura, Shusaku Kuroda, Akihiko Nakahira, Takeshi Nozawa, Kazuya Taniwaki, Kunio Ohtoshi, Takashi Aoyama, Tatsuo Chiba, Hiroshi Enomoto, Kazunori Hirahara, Shigeki Murai, Hiroshi Narayama, Satoshi Yamanaka, Hitoshi Yamazaki, Satoshi Yoshiiri, Ryoukei Azuma, Yasuyuki Baba
    Coastal Engineering Journal 54 (1) 2166-4250 2014/01/01 [Refereed][Not invited]
     
    At 14:46 local time on March 11, 2011, a magnitude 9.0 earthquake occurred off the coast of northeast Japan. This earthquake generated a tsunami that struck Japan as well as various locations around the Pacific Ocean. With the participation of about 300 researchers from throughout Japan, joint research groups conducted a tsunami survey along a 2,000 km stretch of the Japanese coast. More than 5,200 locations have been surveyed to date, generating the largest tsunami survey dataset in the world. The inundation height and run-up height were surveyed by laser, GPS, and other instruments, and the tidal correction has been accurately adjusted using a tidal database and a numerical simulation for Tohoku, an area where tide gauges were destroyed by the tsunami. Based on the survey dataset, the regional and local scale analyses were conducted to understand the basic characteristics of this event. Maximum run-up heights greater than 10 m are distributed along 500 km of coast in direct distance. The affected area of this event was several times larger than historically recorded in Tohoku. The mean inundation height in the southern Sanriku region is 1015 m and there are several peaks of inundation along the coast from the northern to middle part of Sanriku. © 2012 World Scientific Publishing Company and Japan Society of Civil Engineers.
  • WATANABE YASUNORI, TASHIRO KOKI, OTSUKA JUN'ICHI, OYAMA TAKAHIRO, YAMADA TOMOHITO
    土木学会論文集 B2(海岸工学)(Web) Japan Society of Civil Engineers 70 (2) I.56-I.60 (J-STAGE) - I_60 1883-8944 2014 [Not refereed][Not invited]
     
    High speed infrared imaging measurements were performed for identifying mechanical factors to govern surface skin temperatures on wind waves under moderate to strong winds. Surface renewals owing to turbulent disturbances are found to predominantly determine the skin temperature amplitude and phase lags to surface elevation, which is parameterized by a so-called wind-wave Reynolds number (RB). The modulations of the skin temperature variations are observed at RB ~ 4 × 104, indicating governing dynamics to produce surface turbulence is altered at the boundary.
  • Dynamic Interactions of Free-Surface and Vorticity at Water Impacts on Still Water
    Y. Watanabe, A. Saruwatari, D. M. Ingram
    Proc. ICNMMF 2014 [Not refereed][Not invited]
  • Measurement of Dissolved Carbon Dioxide Concentration in a Surf Zone
    J. Otsuka, Y. Watanabe, A. Saruwatari
    Proc. Int. Conf. Coastal Eng. 34 2014 [Not refereed][Not invited]
  • 大塚淳一, 渡部靖憲, 田代晃基, 大山高弘, 猿渡亜由未, 山田朋人
    土木学会論文集 B2(海岸工学)(Web) 70 (2) 41 - 45 1883-8944 2014 [Refereed][Not invited]
  • 馬場 康之, 水谷 英朗, 久保 輝広, 内山 雄介, 森 信人, 渡部 靖憲, 大塚 淳一, 山田 朋人, 猿渡 亜由未, 二宮 順一
    土木学会論文集B2(海岸工学) 公益社団法人 土木学会 70 (2) I_476 - I_480 1884-2399 2014 [Refereed][Not invited]
  • Yasunori Watanabe, Shunichi Sato, Yasuo Niida, Ichiro Kimura, Hiroshi Yokota, Haruhi Oyaizu, Yuki Oshima, Ayumi Saruwatari
    Proceedings of the Coastal Engineering Conference 2014-January 0161-3782 2014 [Refereed][Not invited]
     
    Three-dimensional evolution of local fluid flows and surface shapes under partial collapse of a water column is characterized during computational experiments using three-dimensional large eddy simulation in this paper. The free-surface behaviors highly depend on the collapse level and ambient water layer depth via mechanical interactions between the surface and vortices. It has been found major three modes of the splashing responses of the free-surfaces and vortex structures; (i) forward projection of secondary jets, which organizes a typical rib-like vortex structure stretched underneath the jets, (ii) backward jet projection with an inverse form of the rib structure, and (iii) blob-like waves induced by an array of the horizontal roller vortices. These findings provide new perspectives to understand wave breaking behaviors as well as practical assessments for the fluid responses in the splashing area for sea wall overflow and overtopping.
  • Junichi Otsuka, Yasunori Watanabe
    Proceedings of the Coastal Engineering Conference 2014-January 0161-3782 2014 [Refereed][Not invited]
     
    Instantaneous velocity fields and suspended sediment concentration in surf zones were measured in a wave flume with a sloped sand bed by use of a particle image velocimetry (PIV) and an optical concentration sensor. This was done in order to elucidate sediment transport processes and clarify the relationship between kinetic turbulent energy and sediment suspension under a breaking wave turbulent flow field. In surf zones, sediments become highly suspended when strong turbulent energy reaches the bottom. High concentration was seen in the transition region where turbulent energy is at its maximum. Suspended sediment concentration in a plunging breaker is much higher than that in a spilling breaker because large-scale vortices are typically developed and stir-up much sediment. Suspended sediment is transported to a deeper region due to the undertow becoming highly developed after a wave crest has passed. In shallower regions, suspended sediment concentration increases linearly with an increasing of the turbulent energy. The slope of the approximation line for plunging breakers is steeper than that for spilling breakers.
  • 渡部靖憲, 田代晃基
    土木学会北海道支部論文報告集(CD-ROM) (69) ROMBUNNO.B-42  2013/02 [Not refereed][Not invited]
  • Nobuhito Mori, Yasunori Watanabe, Takayuki Suzuki, Akio Okayasu
    Computational Wave Dynamics 15 - 44 2013/01/01 
    In flow fields, turbulence plays various roles. It produces shear stresses exerted as a Reynolds stress that change the profiles of mean flow, increases the diffusion of substances mixed in a fluid, and dissipates the predominant flow energy through an energy cascade-down process. Turbulence often dominates and characterizes nearshore wave fields involving nearshore currents, breaking waves, and flow fields near bottom surfaces and around structures. In this chapter, the major features of turbulent flows in wave fields and the computational methodologies to model them are first introduced (§2.1). Standard approaches of the Reynolds Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) models are interpreted in §2.2 and 2.3, respectively. Then, in §2.4, these models are applied to several examples of wave-breaking turbulence in the surf zone. Advantageous features and limitations of the current turbulence models are also discussed to provide insight into the directions of future wave-breaking research.
  • Yasunori Watanabe, Nobuhito Mori
    Computational Wave Dynamics 45 - 73 2013/01/01 
    The previous chapter outlined and explained the Navier-Stokes equation. The Navier-Stokes equation describes general fluid flows including the wave field. However, this nonlinear differential equation is very difficult to solve analytically for arbitrary flows. The fluid dynamics of complex flows can be approximated and computed via algebraic solutions of the discretized Navier-Stokes equations using appropriate boundary conditions. Furthermore, a Poisson equation, which is derived from the divergence of the incompressible Navier-Stokes equation, provides the pressure, ensuring a divergence-free velocity field. Due to the assumption of allowing for infinite speed of sound in fluid, this type of differential equation requires a simultaneous solution over the entire computational grid. Because of this, the computational costs become expensive as the total number of grid points in the fluid domain increases. Efficient procedures to solve the simultaneous equations are necessary for practical computations. In this chapter, fundamental procedures to discretize the differential equations on the basis of the finite difference method are discussed in §3.1. Major boundary conditions used in wave computations are introduced in §3.2. And, practical techniques to solve a Poisson-type differential equation are explained in §3.3.
  • Yasunori Watanabe, Nobuhito Mori, Hitoshi Gotoh, Akio Okayasu
    Computational Wave Dynamics 213 - 226 2013/01/01 
    Computational wave dynamics (CWD) is a specialized branch of fluid mechanics to analyze and numerically solve flows under water waves using computational techniques. What distinguishes CWD is the focus on the free-surface of water waves, computing the interfacial interactions, and describing the processes that occur. CWD is a specialized subset of computational fluid dynamics (CFD). A numerical wave flume (NWF) is defined to be a computational simulator of coastal and ocean waves using a CWD model. In this chapter, the current and future prospects of NWF research and applications will be discussed, as they pertain to coastal issues involving sediment transport (§9.1), wave-structure interaction (§9.2), and coastal disasters (§9.3). We also briefly discuss possible avenues of future research within the field of CWD.
  • Yasunori Watanabe
    Computational Wave Dynamics 101 - 136 2013/01/01 
    The Constrained Interpolation Profile (or Cubic Interpolated Pseudo Particle), a so-called CIP method, is a semi-Lagrangian numerical solver for a hyperbolic equation.24, 35 This method explicitly transports a physical quantity and its first derivatives, interpolated over a computing cell by third-order polynomials, along the characteristic curve of the hyperbolic equation. An advantage of this method allows for the computation of the fluid dynamics of moving interfaces, such as compressible fluids around a shock wave, or gas-liquid interfacial flows. Yabe and his colleagues have proposed many versions of CIP methods to extend this application, improving numerical conservation and accuracy. These versions have been applied to wide-ranging scientific and engineering research fields. In this chapter, the theoretical background and standard CIP approach are first interpreted in §5.1. A practical technique for CFD and other versions of CIP are explained in §5.2 and 5.3. Major computational techniques for free-surface flow and applications to water wave computations are introduced in §5.4 and 5.5.
  • 木岡信治, 森昌也, 遠藤強, 竹内貴弘, 渡部靖憲
    土木学会論文集 B3(海洋開発)(Web) 69 (2) 2185-4688 2013
  • 小窪一毅, 中山恵介, 新谷哲也, 柿沼太郎, 大塚淳一, 渡部靖憲, 駒井克昭, SHIMIZU Kenji
    土木学会論文集 B2(海岸工学)(Web) 69 (2) 1883-8944 2013
  • 新井田靖郎, 渡部靖憲
    土木学会論文集 B2(海岸工学)(Web) 69 (2) 1883-8944 2013
  • 渡部靖憲, 泉典洋, 猿渡亜由未
    土木学会論文集 B2(海岸工学)(Web) 69 (2) 1883-8944 2013
  • 渡部靖憲, 堀井正輝, 新井田靖郎
    土木学会論文集 B2(海岸工学)(Web) 69 (2) 1883-8944 2013
  • 渡部靖憲, 佐藤駿一, 三戸部佑太, 横田弘
    土木学会論文集 B2(海岸工学)(Web) 69 (2) 1883-8944 2013
  • KOKUBO Kazuki, NAKAYAMA Keisuke, SHINTANI Tetsuya, KAKINUMA Taro, OTSUKA Jyunichi, WATANABE Yasunori, KOMAI Katsuaki, SHIMIZU Kenji
    Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 公益社団法人 土木学会 69 (2) I_451 - I_455 1884-2399 2013 [Refereed][Not invited]
     
    In enclosed bays, a two-layer system is likely to be formed due to the fresh water from rivers and solar radiation in summer. External forces, such as wind and tide, cause internal waves in a two-layers system, in which the Coriolis effect induces internal Kelvin waves. When internal Kelvin waves propagate over a slope, they break and cause turbulence, which results in the occurrence of horizontal circulation. However, previous studies have not revealed how breaking induces horizontal circulation. Therefore, this study aims to clarify the mechanisms of horizontal circulation induced by the breaking of internal Kelvin waves by using numerical analysis and laboratory experiments.
  • 田中岳, 渡部靖憲, 中津川誠
    土木学会論文集 B2(海岸工学)(Web) 69 (1) 48-63 (J-STAGE)  1883-8944 2013 [Refereed][Not invited]
  • 新井田 靖郎, 渡部 靖憲
    土木学会論文集. B2, 海岸工学 土木学会 69 (2) 46 - 50 1884-2399 2013 [Not refereed][Not invited]
  • 渡部 靖憲, 佐藤 駿一, 三戸部 佑太
    土木学会論文集. B2, 海岸工学 土木学会 69 (2) 176 - 180 1884-2399 2013 [Refereed][Not invited]
  • 渡部 靖憲, 堀井 正輝, 新井田 靖郎
    土木学会論文集. B2, 海岸工学 土木学会 69 (2) 66 - 70 1884-2399 2013 [Refereed][Not invited]
  • 渡部 靖憲, 泉 典洋, 猿渡 亜由未
    土木学会論文集. B2, 海岸工学 土木学会 69 (2) 51 - 55 1884-2399 2013 [Refereed][Not invited]
  • Yuta Mitobe, Yasunori Watanabe
    COASTAL STRUCTURES 2011, VOL 1 & 2 767 - 774 2013 [Refereed][Not invited]
     
    This paper presents a way to quantitatively measure three-dimensional deformations and local failures of wave-dissipating block structures under a series of wave forces in laboratory experiments via a novel image surface shape measurement using single digital camera and PC projector. It was found through the mound stability experiments that the proposing technique is useful for finding local failures of the blocks as well as probability of the displacement of the whole structures, providing reasonable evaluations of stability and performance of coastal structures.
  • K. Nakayama, K. Kokubo, T. Shintani, J. Otsuka, Y. Maruya, Y. Watanabe, K. Komai, T. Okada
    Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 土木学会 68 (2) 926 - 930 1883-8944 2012/11 [Refereed][Not invited]
  • Yasunori Watanabe, Yuta Mitobe, Ayumi Saruwatari, Tomohito Yamada, Yasuo Niida
    Coastal Engineering Journal 54 (1) 2166-4250 2012/03 [Refereed][Not invited]
     
    A numerical computation of the 2011 Tohoku earthquake tsunami was performed to identify fundamental features of the tsunami evolution along the coast of Hokkaido, Japan. Edge waves formed at multiple locations where the refracted tsunami focused, governing local surface oscillations and regional variations in tsunami height along the Pacific coast of Hokkaido. The computation reasonably reproduced the distribution of surveyed tsunami height as well as the time records of surface elevation recorded at ports in Hokkaido. The major features of the frequency spectrum for the 2011 Tohoku tsunami were identical to those for the 2003 Tokachi-oki earthquake tsunami; inherent local properties of surface oscillation caused by the passage of edge waves existed, determined by the local bathymetry. © 2012 World Scientific Publishing Company and Japan Society of Civil Engineers.
  • Watanabe Yasunori, Mitobe Yuta, Saruwatari Ayumi, Yamada Tomohito, Niida Yasuo
    Coastal Engineering Journal World Scientific Publishing 54 (1) 1250002 - 1250002 0578-5634 2012/03 [Refereed][Not invited]
     
    A numerical computation of the 2011 Tohoku earthquake tsunami was performed to identify fundamental features of the tsunami evolution along the coast of Hokkaido, Japan. Edge waves formed at multiple locations where the refracted tsunami focused, governing local surface oscillations and regional variations in tsunami height along the Pacific coast of Hokkaido. The computation reasonably reproduced the distribution of surveyed tsunami height as well as the time records of surface elevation recorded at ports in Hokkaido. The major features of the frequency spectrum for the 2011 Tohoku tsunami were identical to those for the 2003 Tokachi-oki earthquake tsunami; inherent local properties of surface oscillation caused by the passage of edge waves existed, determined by the local bathymetry.
  • 大塚淳一, 渡部靖憲, 林倫史
    土木学会論文集 B2(海岸工学)(Web) 68 (2) 1883-8944 2012
  • 渡部靖憲, 佐藤駿一
    土木学会論文集 B2(海岸工学)(Web) 68 (2) 1883-8944 2012
  • 三戸部佑太, 渡部靖憲
    土木学会論文集 B2(海岸工学)(Web) 68 (2) 1883-8944 2012
  • 渡部靖憲, 堀井正輝
    土木学会論文集 B2(海岸工学)(Web) 68 (2) 1883-8944 2012
  • T. Yanagisawa, H. Saito, Y. Watanabe, Y. Shimizu, H. Hidaka, H. Amitsuka
    Journal of Physics: Conference Series 391 (1) 1742-6596 2012 [Refereed][Not invited]
     
    Ultrasonic investigations of the elastic constants of non-5f compound ThRu2Si2 were performed in order to highlight possible quadrupolar response in the elastic constants of heavy fermion compound URu2Si2, by using the ThRu2Si2 for backgrounds to subtract the phonon contributions in the elastic constants of URu2Si2. We confirmed that the all-elastic constants of ThRu2Si2 show no elastic anomaly, i.e., increasing monotonically and saturating toward low temperatures, which can be understood regular phonon contributions for the solid states. The background-subtracted (C11-C12)/2 of URu2Si2 keeps decreasing with decreasing temperatures from 300 K, while other share modes C44 and C66 show little change. These contrasts suggest that the Γ3-type quadrupole moment O22 will be still dominant and active in URu2Si2 at low temperatures. © Published under licence by IOP Publishing Ltd.
  • Shuzo Takagi, Yasuko Shimizu, Koji Kusaka, Tokishige Fujisawa, Munehiro Fujiwara, Yasunori Watanabe, Tateki Fujiwara
    Nippon Suisan Gakkaishi (Japanese Edition) 78 (2) 246 - 255 0021-5392 2012 [Refereed][Not invited]
     
    To elucidate the threshold amount of DIN value for keeping the nori color, nori color (a* value) and variability of fluval DIN concentration were investigated in the Bisan Strait. The results show that even if oceanic DIN is less than 1 μM, nori can keep its color (a* value> 6) by taking up the DIN supplied intermittently from rivers. In that time, the standard deviation of DIN was larger than 2 μM. At this farm, the total period when DIN> 7 μM was 1.6 hour day -1 this condition coincides with an incubation experiment conducted in a laboratory. The discolored nori transplanted to this place recovered its a* value within 14 days to the same level as that of the nori originally growing at this place.
  • 渡部 靖憲, 堀井 正輝
    土木学会論文集. B2, 海岸工学 土木学会 68 (2) 56 - 60 1884-2399 2012 [Not refereed][Not invited]
  • 大塚 淳一, 渡部 靖憲, 林 倫史
    土木学会論文集. B2, 海岸工学 土木学会 68 (2) 481 - 485 1884-2399 2012 [Refereed][Not invited]
  • 三戸部 佑太, 渡部 靖憲
    土木学会論文集. B2, 海岸工学 土木学会 68 (2) 31 - 35 1884-2399 2012 [Refereed][Not invited]
  • 渡部 靖憲, 佐藤 駿一
    土木学会論文集. B2, 海岸工学 土木学会 68 (2) 41 - 45 1884-2399 2012 [Refereed][Not invited]
  • Junichi Otsuka, Yasunori Watanabe
    Proceedings of the Coastal Engineering Conference 0161-3782 2012 [Refereed][Not invited]
     
    In this study, suspended sediment concentration and velocity in surf zones was measured in a small-scale wave flume with three breaker types (plunging, spilling and intermediate) using an optical concentration sensor and an ultrasonic velocity profiler (UVP). The sediment pickup rate was also calculated from the depth-averaged concentration and the wave energy flux dissipation rate. In plunging breakers, relatively large amounts of sediment are suspended in the transition region due to strong three-dimensional turbulent flows generated by large-scale vortices. In spilling breakers, sediment concentration is lower than that seen in plunging breakers because smaller-scale vortices typically develop below the water surface in the transition region. Concentrations in both breaker types remain at lower levels in bore regions because the vortices fully develop into weak turbulent bores. Comparison in the same range of wave energy flux dissipation rates showed that the sediment pickup rates in these small-scale experiments were approximately 103 times greater than those calculated by Goda (2010) using various data compiled from large-scale experiments and field observations.
  • Yasunori Watanabe, Jun Sakai, Yuta Mitobe, Yasuo Niida
    Proceedings of the Coastal Engineering Conference 0161-3782 2012 [Refereed][Not invited]
     
    The dinoflagellate Pyrocystis lunula emits light in response to water motion. The statistical features of the bioluminescence, emitted by P. lunula, owing to shear stress in oscillatory boundary layer flows over ripped bed were studied in this paper with the aim to develop a new imaging technique for measuring fluid strain rate and shear using plankton that emit light in response to mechanical stimulation. The flash intensity has been found to correlate with fluid strain rate estimated from fluid velocity over ripples. Thus the instantaneous planar distribution of the fluid shear can be estimated from video images of the bioluminescence in a fluid region by using the empirical relation determined in this study.
  • Yasunori Watanabe, Yuta Mitobe, Kaori Oshima
    COASTAL ENGINEERING JOURNAL 53 (4) 549 - 565 0578-5634 2011/12 [Refereed][Not invited]
     
    A novel imaging technique for identifying the locations of free-surface shapes was applied to three-dimensional hydraulic tests of coastal structures. Three-dimensional wave fields, consisting of superposed local reflected and diffracted waves, were measured around a breakwater and the mouth of a model harbor in a laboratory wave basin, and the results are consistent with the predictions of a Boussinesq-type equation model. The new technique was applied to surf zone waves to describe the organized deformation of breaking wave faces that evolve during wave propagation. Typical finger-shaped jets form in the wake of plunging jets, and a local depression trails behind a breaking wave front.
  • Yasunori Watanabe, Yuta Mitobe, Yasuo Niida, Tomohito Yamada
    Proceedings of the International Offshore and Polar Engineering Conference 218 - 223 1098-6189 2011/09/19 [Not refereed][Not invited]
     
    Adaptive mesh refinement (AMR) is one of the powerful computational tools to enhance local computing resolution at less cost. In this paper, computational performances of AMR for tsunami computer simulations were examined in terms of the accuracy and computational cost through computational tests for long wave propagation initiated by collapse of a water column on still water. AMR was also applied to a practical tsunami evolution - 2003 Tokachi-oki earthquake tsunami, which was compared with observed water elevation for examining the applicability of this method to practical tsunami events. It was found through the numerical tests that the present method is capable of efficiently performing reliable computations of tsunami propagation at high resolution. Copyright © 2011 by the International Society of Offshore and Polar Engineers (ISOPE).
  • Yasunori Watanabe, Yasufumi Tanaka
    EXPERIMENTS IN FLUIDS 51 (1) 225 - 236 0723-4864 2011/07 [Refereed][Not invited]
     
    The dinoflagellate Pyrocystis lunula emits light in response to water motion. We developed a new imaging technique for measuring pressure using plankton that emits light in response to mechanical stimulation. The bioluminescence emitted by P. lunula was used to measure impact water pressure produced using weight-drop tests. The maximum mean luminescence intensity correlated with the maximum impact pressure that the cells receive when the circadian and diurnal biological rhythms are appropriately controlled. Thus, with appropriate calibration of experimentally determined parameters, the dynamic impact pressure can be estimated by measuring the cell-flash distribution. Statistical features of the evolution of flash intensity and the probability distribution during the impacting event, which are described by both biological and mechanical response parameters, are also discussed in this paper. The practical applicability of this bioluminescence imaging technique is examined through a water drop test. The maximum dynamic pressure, occurring at the impact of a water jet against a wall, was estimated from the flash intensity of the dinoflagellate.
  • 新井田 靖郎, 渡部 靖憲
    土木学会論文集. B2, 海岸工学 土木学会 67 (2) 66 - 70 1884-2399 2011 [Refereed][Not invited]
  • 森 信人, 加島 寛章, 渡部 靖憲
    可視化情報学会誌 可視化情報学会 31 (1) 63 - 68 0916-4731 2011 [Refereed][Not invited]
  • 三戸部 佑太, 渡部 靖憲
    土木学会論文集. B2, 海岸工学 土木学会 67 (2) 86 - 90 1884-2399 2011 [Refereed][Not invited]
  • 大塚 淳一, 渡部 靖憲
    土木学会論文集. B2, 海岸工学 土木学会 67 (2) 91 - 95 1884-2399 2011 [Refereed][Not invited]
  • 渡部 靖憲, 岩下 厚志
    土木学会論文集. B2, 海岸工学 土木学会 67 (2) 16 - 20 1884-2399 2011 [Refereed][Not invited]
  • 渡部 靖憲, 但木 慎治, 山田 朋人
    土木学会論文集. B2, 海岸工学 土木学会 67 (2) 61 - 65 1884-2399 2011 [Refereed][Not invited]
  • 岩崎 理樹, 渡部 靖憲, 奥寺 亮太
    土木学会論文集. B2, 海岸工学 土木学会 67 (2) 951 - 955 1884-2399 2011 [Refereed][Not invited]
  • Ayumi Saruwatari, Wataru Matsuzaki, Yasunori Watanabe
    Proceedings of the Coastal Engineering Conference 0161-3782 2010/12/01 [Not refereed][Not invited]
     
    A particle imaging measurement of granular particles was applied to fluidized and suspended solid particles involved in steady and unsteady shear flows. In this measurement, 42% sodium iodide solution was used as a fluid medium to coincide the refraction index with the transparent bed material (silica gel). Therefore, the vertical distributions of the granular velocity and turbulent behavior within the bed can be measured by tracking the dyed particles mixed with the bed material. The turbulent kinetic energy in the fluidized layer and particle concentration can also be measured using this technique. The turbulence developed over the bed disturbed the bed material, and as a result the surface particles were lifted and suspended. The underlying mechanism of fluidization and suspension of the sediment seabed in complex turbulent shear flow is believed to be understood through further parametric studies based on the present imaging technique.
  • Junichi Otsuka, Yasunori Watanabe, Ayumi Saruwatari
    Proceedings of the Coastal Engineering Conference 0161-3782 2010/12/01 [Not refereed][Not invited]
     
    In this study, we measured dissolved carbon dioxide (D-CO 2 ) concentration in a surf zone in a laboratory wave flume filled with freshwater and seawater using a glass electrode CO 2 meter, and also observed the air-water turbulent flow field using Particle Image Velocimetry (PIV). D-CO 2 concentration increased with time and the bore region reached a saturated state earlier than the transition region. The gas transfer velocity in the transition region was much higher than that in the bore region since the numerous entrained bubbles trapped within three-dimensional vortices significantly contribute to the gas dissolution into water in the transition region. The gas transfer velocity in a surf zone in freshwater were found to be higher than those in seawater. We estimated the gas transfer velocity in a surf zone from the turbulent energy in breaking waves and the Schmidt number. It was found that the gas transfer velocity could be roughly estimated from the turbulent energy in breaking waves.
  • Yasunori Watanabe, Yuta Mitobe, Yasuo Niida, Ayumi Saruwatari
    Proceedings of the Coastal Engineering Conference 0161-3782 2010/12/01 [Not refereed][Not invited]
     
    A particle / turbulence two-way coupling model, integrated with conventional stochastic and sub-grid stress models of three-dimensional Large Eddy Simulation (LES), has been applied to the particle-laden turbulent flow in a wave boundary layer developed over seabed with the aim to understand dynamic effects of the particle size and number density to the suspension process in shearing flow over the seabed. While the particle size affects local velocity fluctuations, the particle population significantly induces secondary large-scale flows varying over a scale of the wavelength, and intensifies the turbulent energy near the bed. The particle-induced turbulence may result in additional suspension from the bed, causing a recursive suspension process via the particle turbulence interaction in the boundary layer.
  • Y. Niida, Y. Mitobe, Y. Watanabe
    Proceedings of the International Offshore and Polar Engineering Conference 3 750 - 754 1098-6189 2010/09/10 [Not refereed][Not invited]
     
    A two-way stochastic sub-grid bubble model is applied to Large Eddy Simulation (LES) for computing advection and diffusion processes of buoyant air bubbles via turbulence-bubble interactions. The model has been validated through comparisons with previous experiments for bubble rise velocity and fluid turbulence in bubble plumes. It is found that a major feature of the bubble-laden turbulent flow is featured by recursive momentum exchanges between the bubbles and fluid around them - the bubble motion intensifies the fluid turbulence, which also enhances dispersions of the bubbles owing to the intensified turbulence diffusion. © 2010 by The International Society of Offshore and Polar Engineers (ISOPE).
  • Y. Mitobe, Y. Niida, Y. Watanabe
    Proceedings of the International Offshore and Polar Engineering Conference 3 745 - 749 1098-6189 2010/09/10 [Not refereed][Not invited]
     
    This paper presents a novel image measurement technique to measure three-dimensional shapes of solid objects and liquid free-surfaces. In this technique, three-dimensional locations of the surface, where color grids are illuminated by a PC projector, can be estimated from recorded digital images of the grids reflected on the surface. This imaging technique was found to be capable of measuring the three-dimensional coordinates of solid surfaces at high accuracy with mean error less than 0.1 mm through experimental tests. Complex shapes of a breakwater composed of armor block models and of water wave surfaces have been reasonably measured in this technique. © 2010 by The International Society of Offshore and Polar Engineers (ISOPE).
  • 橋本尚棋, 渡部靖憲, 清水康行, 木村一郎, 山口里実, 山口里実
    水工学論文集(CD-ROM) 54 1880-8751 2010
  • Watanabe Yasunori
    Proceedings, ... meeting of Japan Society of Fluid Mechanics 日本流体力学会 2010 (0) 293 - 293 1342-8004 2010 [Refereed][Not invited]
     
    Adaptive mesh refinement (AMR) is one of the powerful computational tools to enhance local computing resolution at less costs. In this paper, computational performances of AMR for tsunami simulations were examined through computational tests for long wave propagation initiated by collapse of the water column on still water in terms of the accuracy and computational cost. AMR was also applied to a practical tsunami evolution-2003 Tokachioki earthquake tsunami, which was compared with measured water elevation for examining the certainties of this method. It was found through the numerical tests that the present method is capable of efficiently performing reliable computations of tsunami propagation at high resolution.
  • 三戸部 佑太, 大島 香織, 渡部 靖憲
    J. JSCE. Ser. B2, Coastal engineering 土木学会 66 (1) 86 - 90 1884-2399 2010 [Not refereed][Not invited]
  • 渡部 靖憲, 石崎 真一郎, 新井田 靖郎
    J. JSCE. Ser. B2, Coastal engineering 土木学会 66 (1) 76 - 80 1884-2399 2010 [Not refereed][Not invited]
  • 渡部 靖憲, 坂井 純
    J. JSCE. Ser. B2, Coastal engineering 土木学会 66 (1) 71 - 75 1884-2399 2010 [Not refereed][Not invited]
  • Ayumi Saruwatari, Yasunori Watanabe, David M. Ingram
    COASTAL ENGINEERING 56 (11-12) 1109 - 1122 0378-3839 2009/11 [Refereed][Not invited]
     
    The local surface deformation resulting from the oblique impact of a columnar water jet has been computed, using a three-dimensional large eddy simulation, as a model of the overturning jet of a breaking wave. The emergence of the secondary jet from the front face of the initial jet has been examined and the organisation of the vortices within the jet characterised. As the secondary jet emerges, the vorticity field becomes unstable under the action of the strong shear beneath the jet surface and pairs of longitudinal counter-rotating vortices stretched along the direction of the jet projection are formed. The presence of these longitudinal vortex pairs creates convergent surface flows, resulting in the formation of longitudinal scars on the rear face of the projecting jet. Following significant growth of the scars on both its upper and lower surfaces, the jet decouples into fingers. The lateral widths of the longitudinal vortices provide a minimum measure of the finger size. A horizontal Froude number Fr(h), representing a measure of strength of horizontal shear in a gravity-dominated impacting flow is defined, which characterises the organisation of the longitudinal vortices occurring in the shear flow, and the resultant formation of scars and fingers. For higher Frh, stronger longitudinal vortices and deeper scars are formed at longer lateral intervals, enhancing the fingering process during the splashing event. Fundamental features of material transport in the vicinity of the surface of jets (e.g. gas transfer across a sea surface) are related to the entrainment of surface fluid by the longitudinal vortices, and is thus also characterised by Frh. (C) 2009 Elsevier B.V. All rights reserved.
  • 渡部 靖憲, 田中 康文, 坂井 純
    Journal of coastal engineering, JSCE 土木学会 56 (0) 831 - 835 0916-7897 2009/10 [Not refereed][Not invited]
  • 渡部 靖憲, 三戸部 佑太
    Journal of coastal engineering, JSCE 土木学会 56 (0) 1466 - 1470 0916-7897 2009/10 [Refereed][Not invited]
  • 猿渡 亜由未, 渡部 靖憲
    Journal of coastal engineering, JSCE 土木学会 56 (0) 16 - 20 0916-7897 2009/10 [Refereed][Not invited]
  • 大塚 淳一, 渡部 靖憲
    Journal of coastal engineering, JSCE 土木学会 56 (0) 91 - 95 0916-7897 2009/10 [Refereed][Not invited]
  • 渡部 靖憲, 石崎 真一郎
    Journal of coastal engineering, JSCE 土木学会 56 (0) 11 - 15 0916-7897 2009/10 [Refereed][Not invited]
  • 渡部 靖憲, 新井田 靖郎, 猿渡 亜由未
    Journal of coastal engineering, JSCE 土木学会 56 (0) 6 - 10 0916-7897 2009/10 [Refereed][Not invited]
  • CHICHIBU Kohtaro, WATANABE Yasunori, SHIMIZU Yasuyuki
    Journal of hydroscience and hydraulic engineering 27 (1) 1 - 10 0912-2508 2009/05/01 [Refereed][Not invited]
  • WATANABE Yasunori, NIIDA Yasuo, SARUWATARI Ayumi, SAEKI Hiroshi
    PROCEEDINGS OF THE JAPANESE CONFERENCE ON COASTAL ENGINEERING Japan Society of Civil Engineers 65 (1) 6 - 10 1884-2399 2009 
    Two-way stochastic subgrid bubble models to determine the number density and sizes of small air-bubbles entrained under circular jets and the advetion and diffusion process for Large Eddy Simulation (LES) are proposed in this paper. The proposing model has been applied to two simple air-water two phase flows - the bubble flow in still water as well as the aerated flow under circular jet flowing into still water. It was found that the bubble motion intensifies the turbulence, which enhances fluctuating bubble motion. This air-water energy tranfer via turbulent interaction is important factor to determine the near-surface fluid dynamics.
  • WATANABE Yasunori, ISHIZAKI Shin-ichiro
    PROCEEDINGS OF THE JAPANESE CONFERENCE ON COASTAL ENGINEERING Japan Society of Civil Engineers 65 (1) 11 - 15 1884-2399 2009 
    A flip-through overtopping jet evolves into laterally deintegrated jets, so-called finger jets, at an early stage of the wave uprush on a vertical wall. The finger jets are vertically stretched to fragment into small multiple droplets or sprays. In this study, these fingering and fragmenting processes were visualized, and the shapes of the jets and sprays were quantitatively measured on the basis of novel level-set image detecting algorithm. The evolution of the size distributions and water volume fractions for the both jets and sprays were characterized via spectrum image analysis.
  • 渡部靖憲, 小玉努
    海洋開発論文集 25 0912-7348 2009
  • 砕波フィンガージェットと飛沫の生成機構
    猿渡亜由未, 渡部靖憲
    混相流学会年会講演会論文集 96 - 97 2009 [Refereed][Not invited]
  • Ayumi Saruwatari, Kota Watanabe, Yasunori Watanabe
    海洋開発論文集 25 837 - 841 0912-7348 2009 [Refereed][Not invited]
  • Yasunori Watanabe, Junichi Otsuka, Ayumi Saruwatari
    COASTAL ENGINEERING 2008, VOLS 1-5 51 - + 0161-3782 2009 [Refereed][Not invited]
     
    Spatial distributions of dissolved carbon dioxide in aerated, strong turbulent flows due to wave breaking are experimentally studied by using image measurements on the basis of Laser Induced Fluorescence (LIF) in this paper. Physical mechanism Of CO2 transport from air to surf zone water is explained in this study - high concentration Of CO2 is dissolved into water via strong mixing of wave surfaces and entrainment of air bubbles after wave breaking, and dissolved CO2 rapidly spreads to wide area due to strong turbulent diffusion. While there is a high correlation Of CO2 concentration and image intensity of the entrained bubbles in a transition region where active jet splashing is undertaken, the mean CO2 concentration is much less than that in a bore region where fully developed turbulence significantly diffuses CO2 within a shallower water region.
  • Ayumi Samwatari, Yasunori Watanabe
    PROCEEDINGS OF COASTAL DYNAMICS 2009 2009 [Refereed][Not invited]
  • Ayumi Saruwatari, Yasunori Watanabe
    COASTAL ENGINEERING 2008, VOLS 1-5 73 - + 0161-3782 2009 [Refereed][Not invited]
     
    Mechanisms for fragmenting a splashing water jet into finger-like smaller jets and sprays are studied by using a three-dimensional large eddy simulation. At an initial stage of splashing, disturbances on free-surfaces of the jet are amplified by shear-induced longitudinal vortices, and typical finger jets are formed at a tip of the projecting jet. The finger jets, which are subjected to surface tension, are consecutively fragmented into smaller sprays. It has been found that the finger width distributions during the fragmenting process can be approximated by a log-normal distribution, and their time variations can be characterized by Froude and Weber numbers. A fragmentation model of the splashing jets, describing evolution of the volume fraction of the fragmented jets, is also developed through computational tests in this paper.
  • Yasunori Watanabe, Shin-ichiro Ishizaki
    PROCEEDINGS OF COASTAL DYNAMICS 2009 2009 [Refereed][Not invited]
  • 渡部 靖憲, 田中 康文
    Journal of coastal engineering, JSCE 土木学会 55 (0) 846 - 850 0916-7897 2008/10 [Refereed][Not invited]
  • 猿渡 亜由未, 渡部 靖憲
    Journal of coastal engineering, JSCE 土木学会 55 (0) 61 - 65 0916-7897 2008/10 [Refereed][Not invited]
  • 渡部 靖憲, 石崎 真一郎
    Journal of coastal engineering, JSCE 土木学会 55 (0) 76 - 80 0916-7897 2008/10 [Refereed][Not invited]
  • MORI Nobuhito, WATANABE Yasunori
    Journal of Japan Society of Fluid Mechanics 日本流体力学会 27 (4) 311 - 320 0286-3154 2008/08/25 [Refereed][Not invited]
     
    A wave breaking in the surf zone generates sea bubbles into the sea and releases air spray into the atmosphere. The sizes of air bubbles and spray are widely distributed from micrometer to centimeter. Moreover, these bubbles and spray are generated inhomogeneously both temporally and spatially. The two-phase flow measurements using imaging technique for two-dimensional bubble measurements are summarized for the surf zone breaking waves. The characteristics of air bubbles and sprays in the surf zone such as number distributions, bubble size spectra, and turbulent characteristics of fluid velocity are reviewed based on the visualization technique developed recently.
  • WATANABE Yasunori, MORI Nobuhito
    J Geophys Res 113 (C7) C07015-C07015-21  0148-0227 2008/07/22 [Refereed][Not invited]
     
    When ocean waves reach a surf zone, jets projecting from the breakers splash sequentially, producing horizontal roller vortices beneath the jets and longitudinal counterrotating vortices behind the rollers; these vortices organize into three-dimensional structures that evolve into a turbulent bore with wave propagation. This disrupts any uniform temperature distributions on the surface, creating heterogeneous patterns of surface temperatures. In this study, we extracted surface temperature distributions from infrared measurements in small- and large-scale wave flumes, then used those data to study the renewed surfaces created by subsurface vortices beneath spilling and plunging breakers. In our large-scale experiments, temporal and spatial scales of surface renewal and surface recovery were consistent with earlier work; however, in our small-scale experiments, the spatial scales showed significant deviations from earlier in situ observations. These inconsistencies may be attributed to scale effects for subsurface vortices, and we show that the Froude number (Fr) can be used to characterize the initial formation of longitudinal counterrotating vortices. Further, for turbulent flows fully developed by wave breaking in a bore region, the frequency of surface renewal correlates exponentially with Reynolds number (Re). The computed vorticity on the breaking wave surface exhibits local patterns which correlate strongly with the gravity induced counterrotating vortices, which in turn renew the rear-facing surface of the breaking waves. In contrast the turbulent bore which precedes the wave crest rapidly disturbs and renews the surface in front of the crest. These two different mechanisms for surface renewal, during the nearshore breaking process, lead to modulations in the surface temperature distribution and changes in thermal diffusivity during the propagation of the breaking wave. Copyright 2008 by the American Geophysical Union.
  • Yasunori Watanabe, Nobuhito Mori
    Journal of Geophysical Research: Oceans 113 (7) 2169-9291 2008/07/08 [Refereed][Not invited]
     
    When ocean waves reach a surf zone, jets projecting from the breakers splash sequentially, producing horizontal roller vortices beneath the jets and longitudinal counterrotating vortices behind the rollers these vortices organize into three-dimensional structures that evolve into a turbulent bore with wave propagation. This disrupts any uniform temperature distributions on the surface, creating heterogeneous patterns of surface temperatures. In this study, we extracted surface temperature distributions from infrared measurements in small- and large-scale wave flumes, then used those data to study the renewed surfaces created by subsurface vortices beneath spilling and plunging breakers. In our large-scale experiments, temporal and spatial scales of surface renewal and surface recovery were consistent with earlier work however, in our small-scale experiments, the spatial scales showed significant deviations from earlier in situ observations. These inconsistencies may be attributed to scale effects for subsurface vortices, and we show that the Froude number (Fr) can be used to characterize the initial formation of longitudinal counterrotating vortices. Further, for turbulent flows fully developed by wave breaking in a bore region, the frequency of surface renewal correlates exponentially with Reynolds number (Re). The computed vorticity on the breaking wave surface exhibits local patterns which correlate strongly with the gravity induced counterrotating vortices, which in turn renew the rear-facing surface of the breaking waves. In contrast the turbulent bore which precedes the wave crest rapidly disturbs and renews the surface in front of the crest. These two different mechanisms for surface renewal, during the nearshore breaking process, lead to modulations in the surface temperature distribution and changes in thermal diffusivity during the propagation of the breaking wave. Copyright 2008 by the American Geophysical Union.
  • Yasunori Watanabe, Nobuhito Mori
    JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 113 (C7) 2169-9275 2008/07 [Refereed][Not invited]
     
    When ocean waves reach a surf zone, jets projecting from the breakers splash sequentially, producing horizontal roller vortices beneath the jets and longitudinal counterrotating vortices behind the rollers; these vortices organize into three-dimensional structures that evolve into a turbulent bore with wave propagation. This disrupts any uniform temperature distributions on the surface, creating heterogeneous patterns of surface temperatures. In this study, we extracted surface temperature distributions from infrared measurements in small- and large-scale wave flumes, then used those data to study the renewed surfaces created by subsurface vortices beneath spilling and plunging breakers. In our large-scale experiments, temporal and spatial scales of surface renewal and surface recovery were consistent with earlier work; however, in our small- scale experiments, the spatial scales showed significant deviations from earlier in situ observations. These inconsistencies may be attributed to scale effects for subsurface vortices, and we show that the Froude number (Fr) can be used to characterize the initial formation of longitudinal counterrotating vortices. Further, for turbulent flows fully developed by wave breaking in a bore region, the frequency of surface renewal correlates exponentially with Reynolds number (Re). The computed vorticity on the breaking wave surface exhibits local patterns which correlate strongly with the gravity induced counterrotating vortices, which in turn renew the rear-facing surface of the breaking waves. In contrast the turbulent bore which precedes the wave crest rapidly disturbs and renews the surface in front of the crest. These two different mechanisms for surface renewal, during the nearshore breaking process, lead to modulations in the surface temperature distribution and changes in thermal diffusivity during the propagation of the breaking wave.
  • Watanabe Yasunori, Saruwatari Ayunii, Ingram David M.
    Journal of Computational Physics Academic Press 227 (4) 2344 - 2365 0021-9991 2008/02/01 [Refereed][Not invited]
     
    A numerical method which fulfils the free-surface boundary conditions and extrapolates the fluid velocity in to empty grid cells outside the fluid region on a fixed Cartesian grid system is presented. The complex, three-dimensional, vortex structures formed via surface/vortex interaction and induction between vortices have been computed using the proposed technique implemented within a level-set method for both vertical and oblique droplet impacts in incompressible fluids. The present results have been validated through numerical tests which confirm zero tangential shear at the free-surface and comparisons with experimental observations of cavity and vortex ring formation underneath the impact location. In some cases, transitions from a concentric vortex ring to a fully three-dimensional vortex structure has been confirmed. Whilst the primary vortex ring is initiated at the highly curved contact surface between the droplet and receiving surface, azimuthal instabilities are manifested in the shear layer around the cavity crater developing after the vertical impact, resulting in axial counter-rotating vorticity between the cavity and descending vortex ring. Underlying mechanisms which induce local deformation of the free-surface, creating a so-called scar, due to the sub-surface vortices at the oblique impacts are also discussed.
  • 秩父宏太郎, 渡部靖憲, 清水康行
    水工学論文集(CD-ROM) 52 1880-8751 2008
  • K. Chichibu, Y. Watanabe, Y. Shimizu
    RIVER, COASTAL AND ESTUARINE MORPHODYNAMICS: RCEM 2007, VOLS 1 AND 2 1 627 - 632 2008 [Not refereed][Not invited]
     
    This paper presents quantitative energy and momentum exchanges between fluid and suspended sands via fluid-sand interactions in open channel flows over sandy dunes through comparisons of the sand-laden flow over movable bed and the single phase flows over the fixed bed, on the basis of double camera PIV measurements with an optical selection technique that is capable of measuring simultaneous velocities for the both water and sand phases at the same locations. Since a boundary shear layer formed behind the dunes is constrained to be developed over a movable bed, the turbulent energy on the separated shear layer is much lower than that in a fixed bed experiment. While the drag acting on the sands significantly decelerates the water flow above the shear layer at the inception of sand suspension, in a settling phase, the drag accelerate the water downward. Additional turbulent energy is induced during sand settlement process, which is over five times higher than the fixed bed case. This additional turbulence may disturb the bed surface and enhance re-suspension of the disturbed sands. This recursive energy and momentum exchanges between the sand and water flows via the suspension, diffusion, settlement and re-suspension processes have important roles to characterize the sand-laden flows over the movable sandy dunes.
  • Yasunori Watanabe, Ayumi Saruwatari
    Proceedings of the Coastal Engineering Conference 62 - 72 0161-3782 2007/12/01 [Not refereed][Not invited]
     
    This paper presents a reasonable method for decomposing instantaneous velocity field in breaking waves, into irrotational, rotational and turbulent velocity components. In this method, Nowgu's approach (1993) for Boussinesq type equation, applying slip bottom velocity computed in a large eddy simulation, is used for estimating the irrotational velocity in breaking waves, and the rotational velocity is obtained on the basis of Helmholtz decomposition. A transition from potential wave energy in incident waves to rotational flows within breaking-induced large-scale vortices and small-scale turbulence through a wave breaking process can be expressed using the proposing decomposition method. © 2007 World Scientific Publishing Co. Pte. Ltd.
  • 渡部靖憲, 宮木康裕, 猿渡亜由未, 田中康文, 大塚淳一, 佐伯浩
    海岸工学論文集 54 (1) 0916-7897 2007
  • OTSUKA Junichi, TANAKA Yasufumi, WATANABE Yasunori
    PROCEEDINGS OF CIVIL ENGINEERING IN THE OCEAN 公益社団法人 土木学会 23 (23) 195 - 200 0912-7348 2007 
    In this study, the mechanism to produce impact pressure on a wall under fresh water and sea water jets is experimentally investigated through water drop tests. The effects of entrapped air, which is a model of an air pocket formed at coastal structure under breaking waves, are also discussed. Higher impact pressure is found to occur under sea water jets rather than fresh water jet for all cases. It is also found that the entrapped air has a role to reduce the pressure maximal and to change peak frequencies of the impacts. New model to estimate variations of the impact pressure with coefficients determined through the experiments is proposed. It is roughly applicable to estimate the maximum pressure and the duration of the impacts under the jets.
  • KASHIMA Hiroaki, MORI Nobuhito, WATANABE Yasunori, OTSUKA Junichi
    PROCEEDINGS OF COASTAL ENGINEERING, JSCE 公益社団法人 土木学会 54 (54) 1466 - 1470 0916-7897 2007 [Refereed][Not invited]
     
    A three-dimensional visualization method (3D-BTV) for bubble measurements was developed to measure bubble shapes and velocities in a liquid. The 3D-BTV method is based on the combination the 3D shadow graph method and 3D super resolution particle tracking velocimetry. The proposed method was verified by virtual experiments and the real measurements of air bubble motions in the water, respectively. In this study, it can be realized that The 3D-BTV method has capability to measure the both bubble shapes and motions in the 3D space with highly temporal-spatial resolution in comparison with the previous technique.
  • WATANABE Yasunori, MIYAKI Yasuhiro, SARUWATARI Ayumi, TANAKA Yasufumi, OTSUKA Junichi, SAEKI Hiroshi
    PROCEEDINGS OF COASTAL ENGINEERING, JSCE 公益社団法人 土木学会 54 (54) 36 - 40 0916-7897 2007 [Refereed][Not invited]
     
    This paper presents a suspended-particle/liquid two-way coupling model integrated with conventional stochastic and subgrid stress models of a large eddy simulation. The model is applied to particle laden turbulent flows in a wave boundary layer developed over a flat sea bed for understanding dynamic effects of turbulence on the particle size, number density and the density. The turbulence intensification due to the presence of particles results in additional suspensions from the bed, featuring a recursive turbulence/suspension interaction process of the particle laden flow within the boundary layer.
  • Dynamics of the local free-surface and sub-surface vortex under splashing jet
    Ayumi Saruwatari, Yasunori Watanabe
    Proc. Int. Conf. Violent Flows (VF-2007) 315 - 318 2007 [Refereed][Not invited]
  • Otsuka Junichi, Watanabe Yasunori
    Proceedings, ... meeting of Japan Society of Fluid Mechanics 日本流体力学会 2007 (0) 47 - 47 1342-8004 2007 [Refereed][Not invited]
     
    Breaking waves produce numbers of vortices through a jet splashing process and also entrain many air bubbles, forming complicated air-water two-phase turbulent flow field in a surf zone. In this research, a simultaneous velocity measurement technique of water and bubble flows in breaking waves is developed for characterizing water-bubble interactions within vortices in a surf zone. The bubbles and neutral buoyant tracers are separately recorded by two different digital video cameras on the basis of an optical filtering technique. It is found that bubble motion does not follow water flow in a vortex, and mean bubble velocity is always higher than water velocity in breaking waves. Bubble-induced turbulent energy is estimated to be less than 10% of total turbulent energy.
  • Yasunori Watanabe, Yoshiyasu Hideshima, Takaaki Shigematsu, Kohsei Takehara
    MEASUREMENT SCIENCE AND TECHNOLOGY 17 (6) 1456 - 1469 0957-0233 2006/06 [Refereed][Not invited]
     
    A new technique of three-dimensional hybrid stereoscopic particle image velocimetry (3D hybrid SPIV) for measuring a volumetric spatial distribution of three-dimensional velocity is presented in this paper. The accuracy and uncertainty of this technique are examined by numerical tests. The 3D hybrid SPIV has been found to be able to measure major features of velocity field involving a vortex with turbulence in a shear flow. This technique is used for measuring an instantaneous three-dimensional flow structure under breaking waves. The formation of the three-dimensional vortex structures involving roller and longitudinal vortices in breaking waves is investigated in this study.
  • 大塚淳一, 渡部靖憲, 横山馨, 武田靖
    海岸工学論文集 53 (1) 0916-7897 2006
  • 大塚淳一, 渡部靖憲
    海岸工学論文集 53 (1) 0916-7897 2006
  • K. Kobayashi, Y. Shimizu, S. Giri, Y. Watanabe
    RIVER FLOW 2006, VOLS 1 AND 2 1221 - + 2006 [Refereed][Not invited]
     
    This paper presents investigations on sand bar formation and evolution process in consequence of unsteady flow. Firstly, experiments have been carried out to investigate the sand bar response to the unsteady flow under laboratory condition. Observations have revealed some notable outcomes, which indicate the effect of unsteady flow condition on sand bar development mechanism. Sand bar evolution in unsteady flow appears to be altered in comparison with sand bar formation under steady flow condition. Furthermore, a two-dimensional morphodynamic model has been developed to reproduce sand bar evolution under unsteady flow condition. Proposed model solves depth-averaged flow equations with a simplest turbulence closure in a generalized coordinate system. A Cubic Interpolated Pseudo-particle (CIP) numerical technique is employed to solve advection phase of momentum equations. Likewise, model solves two-dimensional sediment continuity equation for bedload sediment transport considering the effect of secondary current. Computation has been performed for variety of boundary conditions in upstream and downstream end to evaluate their effect on ultimate results. Results of numerical computation have been verified against laboratory observations. Numerical simulation of aforesaid phenomenon using proposed model has been found to be reasonably consistent.
  • An Outline of Heavy Rainfall Disasters in Hidaka Region, Hokkaido Caused by Typhoon No. 10 in 2003
    K. Hasegawa, T. Araya, T. Ogawa, S. Kikuchi, M. Kuroki, T. Komatsu, H. Saga, Y. Shimizu, O. Shimizu, H. Suzuki, Y. Suzuki, G. Tanaka, H. Tanaka, S. Tohma, M. Nakatsugawa, S. Hatta, Y. Murakami, T. Yamashita, T. Yamada, Y. Watanabe, Y. Watanabe, M. Fujita
    Journal of Hydroscience and Hydraulic Engineering 42 (1) 41 - 56 2006 [Refereed][Not invited]
  • 渡部靖憲, 猿渡亜由未
    海岸工学論文集 53 (1) 71 - 75 0916-7897 2006 [Refereed][Not invited]
  • Numerical method to impose free-surface boundary conditions for local free-surface flows
    Ayumi Saruwatari, Yasunori Watanabe
    Advances in Hydro-science and -Eng. 7 1860/732  2006 [Refereed][Not invited]
  • 秩父 宏太郎, 山下 智子, 渡部 靖憲
    応用力学論文集 土木学会 9 659 - 666 1345-9139 2006 [Refereed][Not invited]
  • 渡部靖憲, 樫野英之, 大島香織
    海洋開発論文集 21 0912-7348 2005
  • 渡部靖憲, 森信人, 秀島賢保
    海岸工学論文集 52 (1) 0916-7897 2005
  • Yasunori Watanabe, Takayuki Otomo, Ayumi Saruwatari
    Journal of coastal engineering, JSCE 52 (1) 736 - 740 0916-7897 2005 [Refereed][Not invited]
  • HASEGAWA Kazuyoshi, SUZUKI Hiroyuki, SUZUKI Yuichi, TANAKA Gaku, TANAKA Hitoshi, TOHMA Satoshi, NAKATSUGAWA Makoto, HATTA Shigemi, MURAKAMI Yasuhiro, YAMASHITA Toshiko, YAMADA Takashi, ARAYAE Tohru, WATANABE Yasuharu, WATANABE Yasunori, FUJITA Mutsuhiro, OGAWA Takehiro, KIKUCHI Shunichi, KUROKI Mikio, KOMATSU Toshimitsu, SAGA Hiroshi, SHIMIZU Osamu
    PROCEEDINGS OF HYDRAULIC ENGINEERING 公益社団法人 土木学会 49 (49) 427 - 432 0916-7374 2005 [Refereed][Not invited]
     
    The typhoon No.10 hit the Pacific cost in Hokkaido on August 9 in 2003. The casualties were 10 killed and 3 wounded. The missing person has not been found yet. This typhoon gave the biggest damage by flood to Hokkaido in the last twenty years. In Saru River basin and Appetu River basin in Ilidaka region, serious damages, such as flooded house, house failure and bridge fall, occurred by this typhoon. Farmland and flood plain were covered for the large sediment.
    In this paper, we will report an outline of heavy rainfall disasters of Hidaka region in Hokkaido by the typhoon No.10. We hope that the result of this investigation helps to clarify the mechanisms of the heavy rainfall disasters with hydrologic and hydraulic knowledge.
  • Watanabe Yasunori, Saeki Hiroshi, Hosking Roger J.
    Journal of Fluid Mechanics Cambridge University Press 545 (545) 291 - 328 0022-1120 2005 [Refereed][Not invited]
     
    The large-scale vortex structures under spilling and plunging breakers are investigated, using a fully three-dimensional large-eddy simulation (LES). When an overturning jet projecting from the crest in a breaking wave rebounds from the water surface ahead, the vorticity becomes unstable in a saddle region of strain between the rebounding jet and a primary spanwise vortex, resulting in spanwise undulations of the vorticity. The undulations are amplified on a braid in this saddle region, leading to a vortex loop with counter-rotating vorticity. This vortex loop consequently envelops adjacent primary vortices, to form a typical rib structure. This rib component (the stretched vortex loop) in the large-scale vortex structure, which intensifies in the strains associated with the multiple primary vortices generated throughout the splash-up cycle, appears to be the previously found obliquely descending eddy.
  • WATANABE Y.
    混相流 18 (3) 巻頭  0914-2843 2004/09/15 [Refereed][Not invited]
  • MORI Nobuhito, WATANABE Yasunori
    Doboku Gakkai Ronbunshu 土木学会 2004 (768) 101 - 111 0289-7806 2004/08/21 [Refereed][Not invited]
     
    Transition of infrared radiation on a sea surface is strongly influenced by reflection of sunlight and sea surface disturbances. The field measurements of breaking waves in surf zone were conducted by the highly sensitive infrared camera. The characteristic changes of infrared images due to bubble formation at the sea surface are discussed. The distinctive patterns of infrared images are associated with the incident wave phase and the wave breaking. The velocity fields on the sea surface are estimated by the PIV method and the correlation between the sea surface velocity and infrared image changes is discussed. The quantitative method to measure sea surface disturbance by the breaking wave is proposed using the infrared radiation image and image processing technique.
  • WATANABE Yasunori, MORI Nobuhito
    Doboku Gakkai Ronbunshu 土木学会 2004 (768) 89 - 100 0289-7806 2004/08/21 [Refereed][Not invited]
     
    Large-scale vortex structures beneath a free-surface in breaking waves are visualised by a characteristic distribution of a surface temperature estimated by infra-red radiation in this paper. Counter-rotating streamwise vortices occurring at wave plunging disrupt a so-called skin layer on the surface to entrain into bulk water underneath the layer. Because of a distinctive difference in temperature between the skin layer and bulk water, the spatial distribution of the surface temperature reflects the intensity of local water mixing on the surface due to the sub-surface stream-wise vortices. Typical length- and time- scales of the stream-wise vortices are determined throughout a surf-zone by utilizing a temperature spectrum and its temporal variation on the basis of the infrared measurements.
  • Yasunori Watanabe, Yuji Yamauchi, Hiroshi Saeki
    Asian and Pacific Coasts, 2003 - Proceedings of the 2nd International Conference 2004 
    This paper describes evolution of population of bubbles and a size distribution through breaking wave process on the basis of an acoustic technique. A surfactant effect to a formation of bubbles is also investigated during lab and in situ experiments. At the inception of a splash-up cycle, the bubbles with specific sizes are predominantly entrained while a bore region contains diverse sizes of the bubbles. Especially, small bubbles tend to increase as a broken wave propagates. The surfactant potentially increases the population, and sea water in a surf zone contains small bubbles much more than fresh water.
  • TAKEUCHI Takahiro, NAKAZAWA Naoki, MIKAMI Takashi, WATANABE Yasunori, SAEKI Hiroshi
    PROCEEDINGS OF CIVIL ENGINEERING IN THE OCEAN 公益社団法人 土木学会 20 (20) 1223 - 1227 0912-7348 2004 [Refereed][Not invited]
     
    Offshore structure made of concrete in ice-covered sea areas is likely to meet an abrasion due to sea ice movement, and needs to be a light weight because of long carriage for its installation. Therefore, it is necessary to determine the thickness of covered concrete with high accuracy. The method to estimate an amount and area of abrasion is shown in considering both local ice pressure distribution and change of water level due to tide. The way to reduce the abrasion is also proposed.
  • SATO Noriyuki, WATANABE Yasunori, HIDESHIMA Yoshiyasu, KONDO Hirofumi, SAEKI Hiroshi
    PROCEEDINGS OF CIVIL ENGINEERING IN THE OCEAN 公益社団法人 土木学会 20 (20) 1305 - 1310 0912-7348 2004 [Refereed][Not invited]
     
    The field measurement of moored ship motions is necessary to decrease troubles in cargo handling. But it was difficult to measure ship motions accurately by using accelerometer.
    In this paper, a 3D PTV algorithm is applied to field observation of moored fishing boat motions. As a result, six-directional ship motions are measured accurately. This observation shows that heaving, rolling and pitching have only one energy peak which is the same period as energy peak of sea wave. Surging, swaying and yawing have two energy peaks, and the energy of peak in long period is higher than the energy of peak in short period. These two peaks are the same period as peaks of sea wave.
  • 渡部靖憲, 秀島賢保, 佐伯浩
    海岸工学論文集 50 (1) 0916-7897 2003
  • 渡部靖憲, 松本卓, 佐伯浩
    海岸工学論文集 50 (1) 0916-7897 2003
  • 渡部靖憲, 山内悠司, 佐伯浩
    海岸工学論文集 50 (1) 0916-7897 2003
  • Masaya Kato, Yasunori Watanabe, Hiroshi Saeki
    Proceedings of the Coastal Engineering Conference 2003- 1661 - 1670 0161-3782 2003 [Not refereed][Not invited]
     
    Wave fields around a breakwater head with wave overtopping were investigated by using large eddy simulation. The complex forms of vortices and Lagrangian vortical fluid motion involved in the vortices were discussed. The three-dimensional eddy structure around a breakwater head is composed of many vortex tubes intertwined and interacting with each other. A complex eddy structure around the breakwater head might cause local scour and promotion of sediment suspension.
  • WATANABE Yasunori
    可視化情報学会誌 = Journal of the Visualization Society of Japan 社団法人 可視化情報学会 22 (0) 383 - 384 0916-4731 2002/07/01 [Refereed][Not invited]
     
    Lagrangian fluid motion under breaking waves and settling motion of glass-particles released into a still water are measured by the 3D stereoscopic particle tracking velocimetry for a large domain (3DSPTV-LD). Since the 3DSPTV-LD dose not require to use a laser sheet for illuminating a single flow plane in a measur domain, it has an advantageous feature in engineering use -i.e. high applicability to 3D measurementsfor a large domain on less costs. In coastal engineering, the large-scale turbulence associated with a large-scale eddy structur, such as a separated vortex array around a structure, which futures three-dimensional behav-iora.is one of the crucial factors affecting sediment transport and stability of a structurc.The 3DSPTV-LD enables it to acquire the 3D large-scale Lagrangian motion over a wide area.
  • Y Watanabe, H Saeki
    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS 39 (7) 607 - 637 0271-2091 2002/07 [Not refereed][Not invited]
     
    The velocity field in breaking water waves is considered in this paper. A numerical simulation describes in detail the transition from a primary overturning and consequent rebounding jets into a bore front, where the vorticity in the coherent large-scale eddy structures devolves into turbulence. Spatial changes in the frequency spectra of the kinetic energy and the enstrophy are associated with the production, transport and dissipation of the Reynolds stress and the various wave and turbulent mixing length scales. Mean velocity fields and the wave and kinetic energy in a surf zone are evaluated. Fourier and wavelet spectral analysis is applied to study both the surface elevation and energy changes, and the distinction that must be made between spilling and plunging breakers is clarified in this paper. Copyright (C) 2002 John Wiley Sons, Ltd.
  • 重松孝昌, 渡部靖憲, 竹原幸生, 奥村悠樹, 小池敏也
    土木学会・海岸工学論文集 49 (1) 791 - 795 0916-7897 2002 [Not refereed][Not invited]
  • Experimental Study on Benthic Fish Habitats in an Ice Covered River
    T. Nogami, Y. Watanabe, M. Nakatsugawa, F. Nakamura, K. Kamura, H. Yamada, S. Tsuchiya, K. Watanabe, H. Iwase
    Ice in the Environment: Proc. of the 16th IAHR International Symposium on Ice, Dunedin, International Association of Hydraulic Engineering and Research 104 - 110 2002 [Refereed][Not invited]
  • Field Experiments for Mitigation Benthic Fish Habitats in the Makomanai River
    T. Nogami, Y. Watanabe, M. Nakatsugawa, F. Nakamura, K. Kamura, H. Yamada, S. Tsuchiya, K. Watanabe, H. Iwase
    River Flow 2002 541 - 549 2002 [Refereed][Not invited]
  • Masaya Kato, Yuhki Okumura, Yasunori Watanabe, Hiroshi Saeki
    Proceedings of the International Symposium on Ocean Wave Measurement and Analysis 2 1126 - 1135 2001/12/01 [Not refereed][Not invited]
     
    In this study, three-dimensional fluid motion in waves around the head of a semi-infinite vertical breakwater was investigated using large-eddy simulation (LES). Wave deformation, separation, and evolution of vortices were investigated to obtain basic data in order to develop a reliable model for predicting local scouring and for estimating local fluid forces acting on the structure. Moreover, the processes by which separated eddies are generated and evolved were discussed in detail in order to determine the mechanisms by which the separated vortices cause local failures of armor blocks and the mound of a breakwater. Two significant vertical separations appeared around both edges of the breakwater head, especially when the wave front passed each edge. The velocity field around the head of the breakwater became significantly three-dimensional because secondary horizontal and helical eddies arose due to the vertical gradient of shear associated with the vertical separation. Furthermore, during interactions among these eddies, a complex three-dimensional eddy structure was formed around the head of the breakwater. It is possible that the vertical velocity caused by the three-dimensional eddy structure is associated with the suspension of sediment around the structure.
  • Yasunori Watanabe, Junichi Ohtsuka, Hiroshi Saeki
    Proceedings of the International Symposium on Ocean Wave Measurement and Analysis 2 992 - 1001 2001/12/01 [Not refereed][Not invited]
     
    In situ visual observations concerning the entrainment of air bubbles after wave breaking were carried out (Kojohama, Ohkishi and Furubira coasts in Japan). This paper presents a discussion of the behavior of air bubbles under breaking waves as well as the effects of these bubbles on the fluid and sediment based on the results of the observations. Typical bubble cloud structures are identified and classified according to the breaker type. Furthermore, the major differences between the three-dimensional eddy structures containing an obliquely descending eddy (ODE) found in the surf zone relative to those in experiments were investigated by tracking the bubbles involved in the vortices.
  • 早川哲也, 森昌也, 山本泰司, 梅沢信敏, 大塚淳一, 渡部靖憲
    海岸工学論文集 48 (1) 0916-7897 2001
  • 渡部靖憲, 大塚淳一, 佐伯浩
    海岸工学論文集 48 (1) 0916-7897 2001
  • Tetsuya Hayakawa, Yasuji Yamamoto, Katsutoshi Kimura, Yasunori Watanabe
    Proceedings of the International Symposium on Ocean Wave Measurement and Analysis 2 1755 - 1762 2001 
    The armor units on the rubble mound foundation of a composite breakwater should be of sufficient mass to ensure stability against storm waves. Toward this, the stability mass of seaward units has been calculated by an equation developed from hydraulic model tests and the mass of leeward units has been designed empirically as half mass of seaward units. This study uses numerical simulation to show that large eddies generated by wave overtopping results in a rapid caissonward flow above the leeward mound crown and that the velocity of this flow is a very important factor in the stability of armor units. Hydraulic model tests were used to formulate a function of wave conditions and structural geometry. From the balance of forces acting on an armor unit, the stability number NS in the Hudson formula was formulated to allow design of armor units on the leeward mound.
  • WATANABE Yasunori, KATO Masaya, YASUHARA Mikio, SAEKI Hiroshi
    PROCEEDINGS OF CIVIL ENGINEERING IN THE OCEAN 公益社団法人 土木学会 17 (17) 287 - 292 0912-7348 2001 
    The Multigrid method (MG) was applied to the 2D and 3D simulations for water waves on various topographies, and the efficiency in terms of computation speed was discussed in this paper. Purpose of this paper is to remove the limitation of computational costs for numerical investigations by introducing MG and to evaluate the availability of this numerical method for practical estimations in the actual wave field. The computational time and number of iteration that MG requires is quantitatively compared with the conventional Gauss-Seidel method (GS). It is found that the MG makes the computational time to save 90-95% for the two-dimensional simulation and 65-80 % for the three-dimensional simulation. Further improvement of the scheme is also discussed in this paper.
  • SAEKI Hiroshi, KAWAI Kunihiro, WATANABE Yasunori, TACHIBANA Harukuni, IMAIZUMI Akira, MATSUO Yuuko
    PROCEEDINGS OF CIVIL ENGINEERING IN THE OCEAN 公益社団法人 土木学会 17 (17) 583 - 587 0912-7348 2001 
    This is a report on the results of experiments aimed to clarfy the optimal section form of sink-and-float type ice boom (SFIB) which may prevent SFIB from becoming buried in send when it sinks and on the results of in site tests at Saroma Lagoon which is located on the Okhotusk sea coast of Hokkaido.
  • 渡部 靖憲, 安原 幹雄, 佐伯 浩
    海岸工学論文集 公益社団法人 土木学会 48 (48) 76 - 80 0916-7897 2001
  • 加藤 雅也, 渡部 靖憲, 佐伯 浩
    海岸工学論文集 公益社団法人 土木学会 48 (48) 786 - 790 0916-7897 2001
  • 渡部 靖憲, 吉川 幹司, 早川 哲也, 佐伯 浩
    海岸工学論文集 公益社団法人 土木学会 48 (48) 821 - 825 0916-7897 2001
  • 奥村 悠樹, 渡部 靖憲, 加藤 雅也, 佐伯 浩
    海岸工学論文集 公益社団法人 土木学会 48 (48) 96 - 100 0916-7897 2001
  • Y Watanabe, M Kato, M Yasuhara, Y Okumura, H Saeki
    PROCEEDINGS OF THE FIRST ASIAN AND PACIFIC COASTAL ENGINEERING CONFERENCE, VOLS 1 AND 2 (APACE 2001) 96 - 105 2001 [Refereed][Not invited]
     
    The multi-grid method is a well-known iterative technique to enhance computational efficiencies. Although there have been a number of investigations on it, dependencies of the computational costs on the presence of free surface and turbulent intensity seem to be still required in terms of computations in coastal engineering. The multi-grid method was applied to two and three-dimensional simulations for water waves on various topographies, and the efficiency in terms of computation costs was discussed in this paper. A purpose of this paper is to reduce the computational costs required by the numerical investigations by introducing the multi-grid method, and to evaluate the efficiency of this numerical method for practical use in the actual wave field. The computing time and number of iterations in the multi-grid method is quantitatively compared with the conventional Gauss-Seidel method. Most interests in this paper are to identify the cost dependencies of this method on the presence of free surface and turbulent intensity. It is found that introducing the multi-grid method can save the computing time 80 - 97 % for two-dimensional simulations and 65 - 80 % for three-dimensional simulations.
  • Y Watanabe, Y Okumura, M Kato, H Saeki
    PROCEEDINGS OF THE FIRST ASIAN AND PACIFIC COASTAL ENGINEERING CONFERENCE, VOLS 1 AND 2 (APACE 2001) 126 - 135 2001 [Refereed][Not invited]
     
    New algorithm of Particle Tracking Velocimetry (PTV) for measuring three-dimensional fluid motion is developed in this paper, and it is examined during the comparison with theoretical and experimental results. The PTV system proposed in this paper has the following advantageous features: 1) Accuracy has less dependencies of the positions and optical axes of video cameras; 2) Accuracy has less dependencies of the type of cameras; 3) Measurement for three-dimensional velocity can be carried out in a large domain on less cost because this system dose not require to use a laser sheet for illuminating the domain. This PTV system is applied for the estimation of the particle velocity under breaking waves and characteristics of the vortical particle motion involved in large-scale eddies are also discussed.
  • Yasunori Watanabe, Mikio Yasuhara, Hiroshi Saeki
    Coastal Engineering 2000 - Proceedings of the 27th International Conference on Coastal Engineering, ICCE 2000 276 942 - 952 2000/12/01 [Not refereed][Not invited]
     
    It can be supposed that fluid motion before wave breaking is two-dimensional in each wave direction. However, wave breaking makes it complex three-dimensional turbulent flow. In this paper, it is discussed what in going on just after wave breaking and how this transition from 2D to 3D happens, based on the numerical results of the Large Eddy Simulation (LES). It is pointed out that, just after the plunging point, the instability associated with vorticity occurs in the high shear flow under breaking waves, and then the 3D velocity field significantly appears and evolves during the wave breaking process. It is also suggested that three-dimensional simulation has to be carried out to estimate the local fluid velocity, which is important factor in terms of sediment transport, in the surf zone, because three-dimensionality of velocity field is significant.
  • 渡部 靖憲, 大塚 淳一, 安原 幹雄, 加藤 雅也, 王 毅, 佐伯 浩
    海岸工学論文集 公益社団法人 土木学会 47 (47) 131 - 135 0916-7897 2000
  • 渡部 靖憲, 安原 幹雄, 佐伯 浩
    海岸工学論文集 公益社団法人 土木学会 47 (47) 146 - 150 0916-7897 2000
  • 加藤 雅也, 奥村 悠樹, 渡部 靖憲, 佐伯 浩
    海岸工学論文集 公益社団法人 土木学会 47 (47) 776 - 780 0916-7897 2000
  • KATO Masaya, WATANABE Yasunori, SAEKI Hiroshi
    PROCEEDINGS OF CIVIL ENGINEERING IN THE OCEAN 公益社団法人 土木学会 16 (16) 75 - 80 0912-7348 2000 [Refereed][Not invited]
     
    The horizontal plate has usually been used for coastal and ocean structures, such as an upper slab of pier and a buffer structure around a bridge pier. And there have been also a lot of research on the use of horizontal plate for submerged breakwater against beach erosion and artificial sea bed for the fish-raising industry. Much effort has so far been devoted to the research of wave fields around a horizontal plate, especially about the impact force to pier and the wave deformation around submerged horizontal plate in terms of the design for the structure. However, the flow pattern around horizontal plate in a wave field has not been explicated. The current study has attempted to numerically analyze some of the wave fields around a horizontal plate. Based on the results of this study, this paper discusses the characteristics of the evolution process of fluid motion and eddy motion around a horizontal plate.
  • S Kioka, Y Yasunaga, Y Watanabe, H Saeki
    PROCEEDINGS OF THE 10TH (2000) INTERNATIONAL OFFSHORE AND POLAR ENGINEERING CONFERENCE, VOL I 1 749 - 755 1098-6189 2000 [Not refereed][Not invited]
     
    Ice scouring is a phenomenon which occurs when moves in contact with seabed. It has been reported to have caused damage to communication cables and water intake pipelines. Therefore, it will be very important to estimate rational maximum scour depth due to complicate behavior of ice, and will also be very important to evaluate forces acting on sea bed and stress that is transmitted via the seabed and deformation of soil. In our previous researches, we concluded that local fluctuations in ice forces (bulldozing forces) in the horizontal direction depended on the slope at the corresponding point on the scour curve(the path of motion of the model ice in plane), and in many cases, ice was tend to move upward. If we understand its mechanisms, we could estimate more rational maximum scour depth. So, it is important to acknowledge the behavior of ice at a time of ice scouring. We have developed the rational experimental device system as compared to previous device system (Kioka and Saeki,1999). Under the renewal conditions, we conducted a lot of test series, and we revealed relationships between ice forces and behavior of ice, variations of its behavior due to varies condition (attack angle, travelling velocity). And we also revealed the probability distribution of some random variable under the same experimental condition.
  • WATANABE Yasunori, SAEKI Hiroshi
    Coast. Eng. J. 41 (3) 281 - 301 0578-5634 1999/12/01 [Refereed][Not invited]
     
    A three-dimensional large eddy simulation (LES) of wave breaking was carried out. A numerical method for LES is proposed in this paper. The following characteristics of vorticity and velocity field after wave breaking are discussed on the basis of results of the LES: (1) generation and evolution of the widthwise (shore direction) velocity component; (2) transition from a two-dimensional velocity field to a three-dimensional one after wave breaking; (3) evolution process of large-scale eddies comprised by horizontal, vertical and helical eddies; and (4) a coherent eddy structure involving a turbulent bottom and wall boundary layer.
  • HAYAKAWA Tetsuya, KIMURA Katsutoshi, HAYASHI Tadashi, DOI Yoshikazu, WATANABE Yasunori
    PROCEEDINGS OF CIVIL ENGINEERING IN THE OCEAN 土木学会 15 (15) 713 - 717 0912-7348 1999 [Refereed][Not invited]
     
    The high mound is sometimes constructed behind a composite breakwater in order to increase the sliding resistance and utilize the mound for an aquacultural purpose. The high mound must be covered by armor units with adequate weight to prevent from scattering by overtopping waves. However, the shallower is the submerged depth of the mound, the heavier become the armor units.
    This study proposed a backward parapet as a countermeasure to reduce weight of armor units. A numerical simulation showed the difference in the velocity field behind the caisson between the backward and forward parapet. With the backward parapet, large-scale eddies were not observed and the velocity on the mound was slower than that of the forward parapet. Furthermore, hydraulic model tests showed that the stable weight was approximately 40% less than that of the forward parapet.
  • HAYAKAWA Tetsuya, KIMURA Katsutoshi, HAYASHI Tadashi, DOI Yoshikazu, WATANABE Yasunori
    Doboku Gakkai Ronbunshuu B 土木学会 15 713 - 717 0912-7348 1999 [Not refereed][Not invited]
     
    The high mound is sometimes constructed behind a composite breakwater in order to increase the sliding resistance and utilize the mound for an aquacultural purpose. The high mound must be covered by armor units with adequate weight to prevent from scattering by overtopping waves. However, the shallower is the submerged depth of the mound, the heavier become the armor units.<BR>This study proposed a backward parapet as a countermeasure to reduce weight of armor units. A numerical simulation showed the difference in the velocity field behind the caisson between the backward and forward parapet. With the backward parapet, large-scale eddies were not observed and the velocity on the mound was slower than that of the forward parapet. Furthermore, hydraulic model tests showed that the stable weight was approximately 40% less than that of the forward parapet.
  • OHSHIMA Kaori, OHTSUKA Natsuhiko, ISHIKAWA Hiroki, TAKAHASI Shinjiro, WATANABE Yasunori, TATIBANA Naokuni, SAEKI Hiroshi
    PROCEEDINGS OF CIVIL ENGINEERING IN THE OCEAN 公益社団法人 土木学会 15 (15) 559 - 564 0912-7348 1999 [Refereed][Not invited]
     
    Development of oil and gas deposits off Sakhalin's northern coast in the sea of Okhotsk are currently under way.An accident involving a spill of crude oil could be expected to affectthe environment and economy of the Hokkaido's Okhotsk coast.If the oil spill occurred in winter season due to the accidents of pipeline, oil tanker and oil rigs, spilled oil would be trapped under the ice floes. If the operation for recovery of spilled oil will be late, spilled oil under the ice floes will be trapped in the ice sheet. In this paper the authors report the behavior of spilled oil trapped under ice sheet and the permeation of spilled oil into ice sheet.
  • WATANABE Yasunori, MATSUMOTO Yasuharu, HAYAKAWA Tetsuya, WANG Yi, OHTSUKA Jun-ichi, YASUHARA Mikio, SAEKI Hiroshi
    PROCEEDINGS OF CIVIL ENGINEERING IN THE OCEAN 公益社団法人 土木学会 15 (15) 375 - 380 0912-7348 1999 [Refereed][Not invited]
     
    When the overturning jet of broken wave hits a wall of coastal structure such as a breakwater, the impact force acts on the structure, which often give a great damage to the structure. Although there have been many reports on the impact force, little is known about the quantitative properties of the force and velocity fluctuation in time. In this paper, the plunging jet attacking to the structure was numerically solved by the direct numerical scheme with the high level of accuracy. The correlations between the surface profiles, the direction of fluid velocity and the pressure were also discussed through the investigations of spatial and temporal changes of them.
  • 渡部靖憲, 森憲広, 佐伯浩
    海岸工学論文集 45 (1) 0916-7897 1998
  • Ohshima Kaori, Usami Norihiro, Takahashi Shinjiro, Kawai Kunihiro, Ohtsuka Natsuhiko, Watanabe Yasunori, Saeki Hiroshi
    PROCEEDINGS OF CIVIL ENGINEERING IN THE OCEAN 公益社団法人 土木学会 14 (14) 435 - 439 0912-7348 1998 
    Development of oil and natural gas deposits off Sakhalin's northern coast on the Sea of Okhotsk are currently under way. Should an accident involving a spill of crude oil or other effluents occur during the development of the oil and natural gas deposits that is currently under way off the eastern coast of northern Sakhalin, it can be expected to have an impact on the environment and economy of the Hokkaido's Okhotsk Sea and Pacific Ocean coast. This paper describes the recovery method for spilled oil under ice floes through the systematic experiments.
  • 渡部靖憲, 松本靖治, 佐伯浩
    海岸工学論文集 公益社団法人 土木学会 45 (45) 136 - 140 0916-7897 1998 [Refereed][Not invited]
  • 渡部 靖憲, 森 憲広, 佐伯 浩
    海岸工学論文集 公益社団法人 土木学会 45 (45) 146 - 150 0916-7897 1998 [Refereed][Not invited]
  • 渡部靖憲, 梅田克史, 佐伯浩
    海岸工学論文集 公益社団法人 土木学会 45 (45) 121 - 125 0916-7897 1998 [Refereed][Not invited]
  • 早川哲也, 渡部靖憲, 鈴木孝信, 木村克俊, 土井善和, 工藤貴弘
    海岸工学論文集 土木学会 45 (2) 691 - 695 0916-7897 1998 [Not refereed][Not invited]
     
    混成堤の基礎捨石マウンドは来襲波浪による散乱や変形を生じないように十分な重量を有する石やコンクリートブロックにより被覆される.防波堤港外側のマウンド被覆材については,谷本ら(1982)や高橋ら(1990)により十分な検討が行われており,設計波浪に対して適切な重量を算定することができる.また,近年では須藤ら(1995)により変形を許容した重量算定法も提案されており,マウンド機能を損なわない程度に重量を低減することができる.これに対して,港内側のマウンド被覆材については港外側重量の25～50%の値が経験的に使用されている.しかしながら,実際には被災事例は極めて少なく,条件によっては被覆工が省略でき工費の縮減が可能になると考えられる.さらに,図-1に示すように防波堤港内側の静穏域に浚渫土砂などの安価な資材を用い藻場造成を目的としたマウンド部を設け,水産生物の生息場として利用する計画がある.この場合,コンブ等が光合成を十分に行えるように,マウンド天端水深を4～5m程度とするため,越波水の打ち込みに対する被覆材の安定性の検討が重要な課題となる.そこで本研究では数値計算および水理模型実験により越波水の打ち込み特性と港内側マウンド被覆材の安定性についての検討を行った.これらの結果により被覆材の移動特性を明らかにするとともに安定重量の算定法を提案する.
  • Takashi Terashima, Fumihiro Hara, Kiyoshi Miyatake, Yasunori Watanabe, Hideki Honda, Hiroshi Saeki
    Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE 1998/01/01 [Not refereed][Not invited]
     
    A systematic research was carried out on abrasion problems caused by movements of sea ice sheets. Research results clarified that the abrasion rate is greatly affected by three features: contact pressure between the sea ice sheet and the surface of a structure; concentration of sand or salinity in sea ice; and properties of materials.
  • S Takahashi, K Ohshima, K Kawai, Y Watanabe, H Saeki
    OIL AND HYDROCARBON SPILLS, MODELLING, ANALYSIS AND CONTROL 333 - 345 1998 [Not refereed][Not invited]
     
    Development of oil and natural gas deposits off Sakhalin's northern coast in the Sea of Okhotsk are currently under way. An accident involving a spill of crude oil or other effluents during the current development of the oil and natural gas deposits off the eastern coast of northern Sakhalin could be expected to affect the environment and economy of the Hokkaido's Okhotsk and Pacific coast. This paper describes a recovery method for spilled oil under the ice flees established through systematic experiment.
  • 早川 哲也, 渡部 靖憲, 鈴木 孝信, 木村 克俊, 土井 善和, 工藤 貴弘
    海岸工学論文集 土木学会 45 (45) 691 - 695 0916-7897 1998 [Refereed][Not invited]
     
    混成堤の基礎捨石マウンドは来襲波浪による散乱や変形を生じないように十分な重量を有する石やコンクリートブロックにより被覆される.防波堤港外側のマウンド被覆材については，谷本ら(1982)や高橋ら(1990)により十分な検討が行われており，設計波浪に対して適切な重量を算定することができる.また，近年では須藤ら(1995)により変形を許容した重量算定法も提案されており，マウンド機能を損なわない程度に重量を低減することができる.これに対して，港内側のマウンド被覆材については港外側重量の25～50%の値が経験的に使用されている.しかしながら，実際には被災事例は極めて少なく，条件によっては被覆工が省略でき工費の縮減が可能になると考えられる.さらに，図-1に示すように防波堤港内側の静穏域に浚渫土砂などの安価な資材を用い藻場造成を目的としたマウンド部を設け，水産生物の生息場として利用する計画がある.この場合，コンブ等が光合成を十分に行えるように，マウンド天端水深を4～5m程度とするため，越波水の打ち込みに対する被覆材の安定性の検討が重要な課題となる.そこで本研究では数値計算および水理模型実験により越波水の打ち込み特性と港内側マウンド被覆材の安定性についての検討を行った.これらの結果により被覆材の移動特性を明らかにするとともに安定重量の算定法を提案する.
  • 渡部靖憲, 森憲広, 稲垣啓, 佐伯浩
    海岸工学論文集 公益社団法人 土木学会 44 (44) 121 - 125 0916-7897 1997
  • Watanabe Yasunori, Saeki Hiroshi, Mori Norihiro, Inagaki Kei
    PROCEEDINGS OF CIVIL ENGINEERING IN THE OCEAN 公益社団法人 土木学会 13 (13) 865 - 870 0912-7348 1997 [Refereed][Not invited]
     
    The velocity field in a surf zone was experimentally investigated, and the effects of an undertow after wavebreaking on turbulence and wave motion are discussed. In order to reveal the mechanisms of sand suspension overthe bottom, the measurement of velocity distribution of sand transportation was tried by the particle imagevelocimetry.
    It is important to understand the reciprocal relationship between turbulence caused by wave breaking anda cross-shore steady flow, such as a rip current or an undertow, as both of these are closely related to sedimentrolling up and cross-shore sediment transport. On the other hand, high-strain turbulent flows that have threedimensionallycoherent eddy structures with oblique vortexes are generated in a surf zone, and the steady flow isstrongly influenced by the three-dimensional vortexes generated at thistime. This study was designed to investigatethe three-dimensional characteristics of the velocity field and bed erosion in a surf zone, and the effects of undertowon them, of undertow on them, in order to clarify the mechanisms of fluid motion and the cross-shore sedimenttransport in this region.
  • Hayakawa T., Kitamura T., Sato M., Kinosita C., Watanabe Y., Saeki H.
    PROCEEDINGS OF CIVIL ENGINEERING IN THE OCEAN 公益社団法人 土木学会 13 (13) 837 - 842 0912-7348 1997 [Refereed][Not invited]
     
    It is cralified that doubly placed submerged break waters reduce the incident wave height effectively where the tidal range is small.
    Coastal structures constracted in Ohotuku Sea coast of Hokkaido have been attacked by water waves and drifting ice floes. In this paper, the authors cralified the stability of armor stones on doubly placed submerged breakwaters whitch are attacked by waves and ice floes through systematic experiments.
  • Y Watanabe, N Mori
    PROCEEDINGS OF THE SEVENTH (1997) INTERNATIONAL OFFSHORE AND POLAR ENGINEERING CONFERENCE, VOL III, 1997 3 247 - 253 1098-6189 1997 [Not refereed][Not invited]
     
    The velocity field in a surf zone was experimentally investigated, and the effects of an undertow after wave breaking on turbulence and wave motion are discussed The mechanisms of production and transportation of three-dimensional turbulence in a surf zone are also discussed. It is important to understand the reciprocal relationship between turbulence caused by wave breaking and a cross-shore steady flow, such as a rip current or an undertow, as both of these are closely related to sediment rolling up and cross-shore sediment transport. On the other hand, high-strain turbulent flows that have three-dimensionally coherent eddy structures with oblique vortexes are generated in a surf zone, and the steady flow is strongly influenced by the three-dimensional vortexes generated at this time. However, these have been few investigations of this problem. Therefore, this study was designed to investigate the three-dimensional characteristics of the velocity field and bed erosion in a surf zone, and the effects of undertow on them, in order to clarify the mechanisms of fluid motion and the cross-shore sediment transport in this region.
  • 渡部靖憲, 佐拍浩
    海岸工学論文集 公益社団法人 土木学会 43 (43) 71 - 75 0916-7897 1996
  • 佐藤幸雄, 渡部靖憲
    海岸工学論文集 公益社団法人 土木学会 43 (43) 911 - 915 0916-7897 1996
  • Y Watanabe, H Saeki
    HYDRAULIC ENGINEERING SOFTWARE VI 385 - 394 1996 [Refereed][Not invited]
     
    Two-dimensional wave motion in a surf zone was numerically solved to obtain temporal and spatial characteristics of the velocity field and energy dissipation, and these results were compared with measurements by the particle image velocimetry. This direct numerical analysis can express splash-up and propagation of a front bore with large vortexes after breaking. The characteristics of vorticity and energy dissipation for a plunging breaker, which vary in a complicated manner with space and time, were also investigated.
  • Watanabe Yasunori, Mori Norihiro, Kuroki Mikio, Saeki Hirosi
    PROCEEDINGS OF CIVIL ENGINEERING IN THE OCEAN 公益社団法人 土木学会 12 (12) 37 - 42 0912-7348 1996 [Refereed][Not invited]
     
    Three-dimensional fluid velocity field in a surf zone was experimentally investigated to obtain spatial characteristics of mean flow, such as return current, and turbulence flow caused by wave breaking. It is possible that three-dimensional organized vorticities, generated after breaking, indirectly affect to mean flow and induce three-dimensional steady flow. In two-dimensional wave flume, return current contributes three-dimensionality of fluid motion in a surf zone. The effect of return current to a front bore is also investigated by the particle image velocimetry.
  • Terashima Takashi, Nakazawa Naoki, Kioka Shinji, Watanabe Yasunori, Saeki Hiroshi
    Doboku Gakkai Ronbunshuu B Japan Society of Civil Engineers 11 235 - 239 0912-7348 1995
  • Orihashi Tsuneharu, Watanabe Yasunori, Hamanaka Ken-ichiro
    PROCEEDINGS OF CIVIL ENGINEERING IN THE OCEAN 公益社団法人 土木学会 11 (11) 1 - 6 0912-7348 1995 
    For the problem of diffraction and radiation of water waves from an arbitrary shapcd body, John's Green function (1950) has been used by several authors. However this John's Green function seems to have a ill behavior when the problem solved numerically through discretization.In this paper we point out that this ill behavior is caused from the definition of delta function which is used by John, and propose a new Green function as a Modified Green function, and check the application of this Green function for wave field.
  • Y WATANABE, H SAEKI, K HAMANAKA
    PROCEEDINGS OF THE FIFTH (1995) INTERNATIONAL OFFSHORE AND POLAR ENGINEERING CONFERENCE, VOL III 1995-June 64 - 69 1098-6189 1995 [Refereed][Not invited]
     
    The kinematic energy loss of fluid over the rippled bed under the oscillatory flow, and the wave attenuation it causes, is investigated by numerical analysis. When surface waves propagate in shallow water regions, the flow field near the rough bottom become complex structures with separation and turbulence. We have succeeded in explaining numerically the flow field over the ripple for a relative high-Reynolds number. The spatial and temporal characteristics of the energy loss are investigated in detail.The energy loss of fluid over the ripple results in significant wave attenuation as a practical problem, especially for laboratory experiments. This problem is discussed by comparing numerically the reduction of wave height in the field and in a wave flume applying the Froude similitude.
  • 奥村慎也, 佐藤幸雄, 渡部靖憲
    海岸工学論文集 公益社団法人 土木学会 42 (42) 831 - 835 0916-7897 1995 [Refereed][Not invited]
  • 渡部靖憲, 佐伯浩
    海岸工学論文集 公益社団法人 土木学会 42 (42) 116 - 120 0916-7897 1995 [Refereed][Not invited]
  • 渡部靖憲, 細川裕希, 佐伯浩
    海岸工学論文集 公益社団法人 土木学会 42 (42) 106 - 109 0916-7897 1995 [Refereed][Not invited]
  • 折橋恒春, 渡部靖憲, 浜中建一郎
    海岸工学論文集 公益社団法人 土木学会 41 (41) 26 - 30 0916-7897 1994 [Refereed][Not invited]
  • Y. Watanabe, T. Orihashi, K. Hamanaka, Y. Sato
    National Conference Publication - Institution of Engineers, Australia 1 (93 pt 4) 229 - 234 0313-6922 1993/01/01 [Not refereed][Not invited]
     
    A numerical analysis is performed to investigate the detail of flow in low-Reynolds and low-Strouhal numbers. The numerical result have good agreements with experimental data. Vorticity, stream function, pressure field and in-line force are investigated in detail. Morison equation fails to predict maximum in-line force in the flow with significant separations. When the significant separations occur, impulsive in-line force appears and its time phase corresponds to the phase when the separations have just started to develop.
  • 近藤よし郎, 渡部靖憲, 山上佳範, 杉岡一郎
    海岸工学論文集 Japan Society of Civil Engineers 39 (2) 1061 - 1065 0916-7897 1992/11 [Not refereed][Not invited]
  • ISHII CHIMATARO, SATO HIDEYASU, ORITANI NORIHIRO, WATANABE YASUNORI, SAEKI HIROSHI, YAMASHITA TOSHIHIKO
    海洋開発論文集 Japan Society of Civil Engineers 8 195 - 199 0912-7348 1992 [Not refereed][Not invited]
     
    Recently, caisson type structures have been employed as offshore structures in regions of extreme cold. As the liquid, sand or gravel filling proceeds, the caisson freezes and the internal pressure rises. It has previously been verified that this pressure rise, due to an increase of volume caused by ice growth, depends strongly upon the permiability coefficient of the sea ice forming within the sands and gravels. This paper deals with the variation of inner pressure in two kinds of model caissons due to ice growth.
  • Y WATANABE, K KAWAI
    GASTROENTEROLOGIA JAPONICA 26 258 - 261 0435-1339 1991/07 [Refereed][Not invited]
  • Shizuo Tsunogai, Shinichiro Noriki, Koh Harada, Taro Kurosaki, Yasunori Watanabe, Masaru Maedaa
    Journal of the Oceanographical Society of Japan 42 (2) 83 - 90 0029-8131 1986/04 
    Settling particles were collected at 1,460 m and 3,760 m depth in the Antarctic Ocean with sediment traps of time series type. The total deployment period of 40 days was divided into four terms of 10 days each. Seawater samples were collected both at deployment and retrieval of the traps at each site. During the 42 days the concentration of silicate in the surface water decreased by 32%, whereas those of nitrate and phosphate decreased by only 4-5%. The total particulate flux in the Antarctic Ocean is the largest among those hitherto observed in the world ocean. The time variation of the particulate flux at 1,460 m depth almost coincided with that at 3,760 m. The settling particles were comprised roughly of 80% biogenic silica, 15% organic matter and 5% other substances including sea salt. The clay fraction was only 0.05% at 1,460 m depth. The settling flux of biogenic silica agrees fairly well with the calculated rate of change in the concentration of silicate in the surface 100 m. Thus it is concluded that preferential propagation of diatoms reduces the concentration of silicate prior to other nutrients in the Antarctic Ocean. © 1986 Oceanographical Society of Japan.
  • Y. Watanabe, S. Tsunogai
    Marine Chemistry 15 (1) 71 - 83 0304-4203 1984/08 
    Sediment core samples were taken once a month from July 1980 to September 1981 at a station in Funka Bay (92-m depth) for the determination of phosphate, silicate and alkalinity in interstitial water. A remarkable seasonal variation was found for interstitial phosphate, that is, distinct maxima appeared in spring (March-April), just after a phytoplankton bloom which brought a large amount of settling particles to the bottom, and in summer (July-August) when the water was stratified and the dissolved oxygen content of the bottom water decreased due to the decomposition of organic matter. The high interstitial phosphate concentration was always accompanied by a sharp increase in alkalinity, indicating sulfate reduction. This large seasonal variation in interstitial phosphate cannot be explained by in situ decomposition of organic matter and/or the diffusive loss of interstitial phosphate. A more likely explanation is adsorption and desorption of interstitial phosphate coincident with the depth of the active sulfate reduction layer. © 1984.
  • Shizuo Tsunogai, Yasunori Watanabe
    Journal of the Oceanographical Society of Japan 39 (5) 231 - 239 0029-8131 1983/10 
    The spring bloom of phytoplankton was studied in March in Funka Bay, Japan, to test the Tsunogai (1979)'s hypothesis regarding the role of silicate in the bloom. The hypothesis comprises two parts. 1) Diatoms are predominant when all the physical and chemical conditions are adequate for plankton growth. 2) Since the Si:P ratio of the diatom body is usually much larger than that of sea water, flagellates (non-siliceous phytoplankton) replace diatoms after dissolved silicate in the sea water has been almost completely consumed by diatoms. At the end of the bloom in late March phosphate still remained in the water but silicate was exhausted and the main species of phytoplankton changed from diatoms to flagellates. Grazing pressure by zooplankton at this time was not so great. A model using the data on assimilation rates of silicate showed a dramatic change of silicate uptake in late March. Poison in scallops caused by Protogonyaulux sp. (dinoflagellates) rapidly increased from mid-April at all stations along the coast of Funka Bay. All of these findings support Tsunogai's hypothesis. © 1983 The Oceanographical Society of Japan.
  • Shizuo Tsunogai, Yasunori Watanabe
    GEOCHEMICAL JOURNAL 15 (2) 95 - 107 0016-7002 1981 
    The concentrations of Ca in the surface and deep waters of the North Pacific and the Bering Sea have been determined with a highly precise method. The deep water contains Ca relative to chlorinity by 0.8% more than the warm surface water of the western North Pacific, whereas it contains Ca by only 0.4% more than does the cold surface water of the northern North Pacific. Based on the results the amount of Ca dissolved in the deep water column of 4km long is calculated to be 9gCa/m2/yr. In the surface water of the productive Bering Sea, alkalinity is found to be controlled chiefly by the formation and decomposition of organic matter rather than the formation and dissolution of CaCO3. Furthermore a plot of Ca versus potential alkalinity defined by Brewer et al. (1976) gives virtually a slope of 0.5 for upper waters above 1.5 km depth. It, however, is difficult to demonstrate the relation between Ca and alkalinity for the deep water collected from the northern North Pacific alone. © 1981, GEOCHEMICAL SOCIETY OF JAPAN. All rights reserved.

MISC

  • 平野誠治, 奈良俊介, 水口陽介, 早川哲也, 本多和彦, 森信人, 渡部靖憲, 木村克俊  土木学会論文集(Web)  79-  (18)  2023
  • 佐藤典之, 早川哲也, 岩崎慎介, 大塚淳一, 平野誠治, 本多和彦, 森信人, 渡部靖憲, 木村克俊  土木学会論文集(Web)  79-  (17)  2023
  • 粕谷有汰, 猿渡亜由未, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (79)  2023
  • 中山晴生, 猿渡亜由未, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (79)  2023
  • 大和田宏太朗, 猿渡亜由未, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (79)  2023
  • 齋藤翔大, 猿渡亜由未, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (79)  2023
  • 渡部靖憲, 南健人, 猿渡亜由未, 馬場康之, 久保輝広, 森信人, 内山雄介, 志村智也, 大塚淳一, 新井田靖郎, 二宮順一  土木学会論文集(Web)  79-  (17)  2023
  • 猿渡亜由未, 齋藤翔大, 渡部靖憲  土木学会論文集(Web)  79-  (17)  2023
  • 渡部靖憲, 菊池陸, 猿渡亜由未  土木学会論文集(Web)  79-  (17)  2023
  • 野村明弘, 猿渡亜由未, 渡部靖憲  土木学会論文集(Web)  79-  (17)  2023
  • 野村明弘, 佐藤典之, 石川浩希, 早川哲也, 岩崎慎介, 大塚淳一, 森信人, 渡部靖憲  土木学会論文集 B2(海岸工学)(Web)  78-  (2)  2022
  • 渡部靖憲, 藤澤蓮, 猿渡亜由未  土木学会論文集 B2(海岸工学)(Web)  78-  (2)  2022
  • 猿渡亜由未, 小林正法, 渡部靖憲  土木学会論文集 B2(海岸工学)(Web)  78-  (2)  2022
  • 猿渡亜由未, 今南実, 渡部靖憲  土木学会論文集 B2(海岸工学)(Web)  78-  (2)  2022
  • 土屋裕嵩, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (78)  2022
  • 七澤梨花, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (78)  2022
  • 小嶋亮太, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (78)  2022
  • 小熊多佳史, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (78)  2022
  • 藤澤蓮, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (78)  2022
  • 黒田晴希, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (78)  2022
  • 小嶋亮太, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (77)  2021
  • 土屋裕嵩, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (77)  2021
  • 小熊多佳史, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (77)  2021
  • 野中拓実, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (77)  2021
  • 渡邊健太, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (77)  2021
  • 渡部靖憲  京都大学防災研究所年報(Web)  (64A)  2021
  • 足立天翔, 猿渡亜由未, 宮武誠, 渡部靖憲  混相流シンポジウム講演論文集(Web)  2019-  ROMBUNNO.B212_0114 (WEB ONLY)  2019  [Not refereed][Not invited]
  • 津田洋輔, 渡部靖憲, 猿渡亜由未  混相流シンポジウム講演論文集(Web)  2019-  ROMBUNNO.B223_0124 (WEB ONLY)  2019  [Not refereed][Not invited]
  • 早川健, 津田洋輔, 杉村一直, 石見翔汰, 渡部靖憲, 猿渡亜由未  土木学会北海道支部論文報告集(CD-ROM)  (75)  ROMBUNNO.B‐07  2019/01  [Not refereed][Not invited]
  • 津田洋輔, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (75)  ROMBUNNO.B‐14  2019/01  [Not refereed][Not invited]
  • 足立天翔, 猿渡亜由未, 宮武誠, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (75)  ROMBUNNO.B‐06  2019/01  [Not refereed][Not invited]
  • 横内浩志, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (75)  ROMBUNNO.B‐12  2019/01  [Not refereed][Not invited]
  • 鈴木敦貴, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (75)  ROMBUNNO.B‐18  2019/01  [Not refereed][Not invited]
  • 大庭健輔, 猿渡亜由未, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (75)  ROMBUNNO.B‐20  2019/01  [Not refereed][Not invited]
  • 山下賢人, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (75)  ROMBUNNO.B‐11  2019/01  [Not refereed][Not invited]
  • 門脇壮健, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (75)  ROMBUNNO.B‐10  2019/01  [Not refereed][Not invited]
  • 福原康平, 猿渡亜由未, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (75)  ROMBUNNO.B‐04  2019/01  [Not refereed][Not invited]
  • 杉村一直, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (75)  ROMBUNNO.B‐08  2019/01  [Not refereed][Not invited]
  • 野中拓実, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (75)  ROMBUNNO.B‐21  2019/01  [Not refereed][Not invited]
  • Sediment suspension in violent breaking waves
    Yasunori Watanabe, Ayumi Saruwatari  12th European Fluid Mechanics Conference  2018/09  [Not refereed][Not invited]
  • 猿渡亜由未, 渡部靖憲  北海道地区自然災害科学資料センター報告  31-  31‐42  2018/03/31  [Not refereed][Not invited]
  • Yasunori Watanabe, Kazunao Sugimura, Ayumi Saruwatari  混相流シンポジウム講演論文集(Web)  2018-  WEB ONLY  2018  [Not refereed][Not invited]
  • 馬場 康之, 水谷 英朗, 久保 輝広, 内山 雄介, 森 信人, 渡部 靖憲, 山田 朋人, 猿渡 亜由未, 大塚 淳一, 二宮 順一  京都大学防災研究所年報. B = Disaster Prevention Research Institute Annuals. B  60-  (0)  664  -671  2017/09  [Refereed][Not invited]
  • 渡部靖憲  土木学会誌  102-  (8)  44‐45  2017/08/15  [Not refereed][Not invited]
  • 福原康平, 本間翔希, 猿渡亜由未, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (73)  ROMBUNNO.B‐52  2017/02  [Not refereed][Not invited]
  • 岡地寛季, 山田朋人, 渡部靖憲, 猿渡亜由未, 大塚淳一, 森信人, 馬場康之, 水谷英朗, 久保輝広, 二宮順一, 内山雄介  土木学会北海道支部論文報告集(CD-ROM)  (73)  ROMBUNNO.B‐04  2017/02  [Not refereed][Not invited]
  • OKACHI Hiroki, YAMADA Tomohito, Watanabe Yasunori, OOTSUKA Junichi  Proceeding of Annual Conference  30-  (0)  95  -95  2017  [Refereed][Not invited]
     
    海面由来の砕破飛沫に着目した研究では，大気海洋間での運動量・熱交換に与える飛沫の影響が議論されている．現在，海面抵抗は風速が大きくなるにつれて増加するとされている．しかし風速30m/s以上の暴風下では発達した風波と海表面上に分布する砕破飛沫の影響により海面の抵抗が著しく低下-若しくは一定になるという提案がある．砕破飛沫は蒸発することで周りの大気から潜熱を奪う冷却効果を持つ．潜熱を吸収し温度上昇した飛沫が海面に落下することで海面水温を上昇させる．このプロセスにより飛沫が大気海洋間の熱交換に影響を与える．この過程を解明するために飛沫観測する必要があるが，暴風雨下では降雨を伴うため飛沫の物理過程の解明は困難である．一方で雨滴に着目をすると，海洋及び陸での降雨観測は地球全体の水循環を把握するために不可欠である．しかし海洋観測では降雨のみならず砕破飛沫の混合が考えられる．そのため飛沫及び降雨の研究において両者を分類することは不可欠である．本研究では和歌山県田辺湾沖での雨滴及び砕破飛沫の直接観測と砕破飛沫の室内風洞実験を試みた．<br /> 野外観測では雨滴と砕破飛沫の混合したデータから両者を分類し，砕破飛沫の粒径分布を抽出した．また降雨時の粒径分布では風速の増加と共に飛沫の影響と考えられる1mm以下の粒径を持つ粒子数の増加が確認できた．室内実験からは風速が増加するに連れて粒子数の増加，体積の増加，運動量交換に寄与する抵抗係数の減少が確認できた．
  • 渡部 靖憲, 猿渡 亜由未  北海道地区自然災害科学資料センター報告 = Bulletin of the Natural Disaster Science Data Center, Hokkaido  29-  23  -34  2016/03  [Refereed][Not invited]
  • 一瀬輪子, 北野慈和, 山田朋人, 渡部靖憲, 泉典洋  土木学会北海道支部論文報告集(CD-ROM)  (72)  2016
  • Okachi Hiroki, Yamada Tomohito, Watanabe Yasunori, Saruwatari Alum, Otuka Junichi, Mori Nobuhito, Baba Yasuyuki, Mizutani Hideaki, Kubo Teruhiko, Ninomiya Junnichi, Uchiyama Yuusuke  Proceeding of Annual Conference  29-  (0)  35  -35  2016  [Not refereed][Not invited]
     
    Associated with global warming, the effects of sea level rise are linked to frequency and intensity of storms and other weather events. Previous researches argue that sea spray affects the development of typhoons. This study reports a marine observation on Tanabe bay near Wakayama Prefecture utilizing a measurement instrument called parsivel. Parsivel can detect the diameter of a droplet and the distribution of velocity. In our observation point, we reveal the presence of spray droplets with 1.5mm ~ 5.510mm diameter when typhoon events occurs in 2015. We discuss the relationship between sea spray and wind velocity when storm events occurs.<br>
  • 馬場 康之, 水谷 英朗, 久保 輝広, 内山 雄介, 森 信人, 渡部 靖憲, 山田 朋人, 猿渡 亜由未, 大塚 淳一, 二宮 順一  京都大学防災研究所年報  (60)  664  -671  2016  [Refereed][Not invited]
  • WATANABE Yasunori  Fluids engineering conference ...  2015-  "0327  -1"-"0327-2"  2015/11/07  
    When a wave-breaking jet plunges onto the forward wave trough, three-dimensional organized free-surface flows with longitudinal counter-rotating vortices are organized at the plunging location. The finger jets are induced through free-surface entrainment by the vortices beneath the surface. The surface tension destabilize the jets to form multiple droplets. Fundamental features of the series of free-surface deformation during the wave breaking process are studied on the basis of numerical computations and laboratory experiments.
  • 岡地寛季, 山田朋人, 渡部靖憲, 猿渡亜由未, 大塚淳一, 馬場康之, 水谷英朗, 久保輝広, 二宮順一, 内山雄介, 森信人  地球環境シンポジウム講演集  23rd-  149  -150  2015/09/02  [Not refereed][Not invited]
  • 新井田 靖郎, 渡部 靖憲  地球環境シンポジウム講演集  23-  109  -112  2015/09
  • KIOKA SHINJI, TAKEUCHI TAKAHIRO, WATANABE YASUNORI  混相流  29-  (2)  124  -131  2015/06/15  [Not refereed][Not invited]
     
    East coasts of Hokkaido, facing Okhotsk Sea and Pacific Ocean, are covered by sea ice drifted from northern Okhotsk Sea in late January through early of March. When tsunami occurs during the term and arrives at the ice-covered coasts, the disaster risks are significantly increased since ice floes carried by run-up tsunami can extend the possible damages through distinct dynamic behaviors occurring in ice-floe-laden flows; that is, forming pile-ups and jams of the ice floes, and enhancing ice and hydraulic forces. In this paper, features of the previous damages to residences and infrastructures by sea ice for the 1952 Tokachi-oki tsunami and the 2011 Tohoku tsunami are firstly discussed for charactering the ice-structure interactions. The fracture mechanisms of the ice floes colliding to structures during jamming and piling-up processes are identified on the basis of model experiments as well as numerical computations using a 3D Distinct Element Method. We also find structures with openings, such as windows and space between columns, induce ice jams and pile-ups and dam up the run-up flows, resulting in downstream water level rise and thus significant increase of hydraulic pressure acting on the structure, which indicates the increased risks expected in urban area.
  • 一瀬輪子, 山田朋人, 北野慈和, 渡部靖憲, 泉典洋  土木学会北海道支部論文報告集(CD-ROM)  (71)  2015
  • 北野 慈和, 一瀬 輪子, 山田 朋人, 渡部 靖憲, 泉 典洋  大会講演予講集  107-  267  -267  2015  [Refereed][Not invited]
  • 馬場 康之, 水谷 英朗, 久保 輝広, 内山 雄介, 森 信人, 渡部 靖憲, 山田 朋人, 猿渡 亜由未, 大塚 淳一, 二宮 順一  京都大学防災研究所年報  (59)  431  -437  2015  [Refereed][Not invited]
     
    This paper shows some results of a field observation carried out in the summer of 2015. The vertical profiles of currents and water temperature have been measured as well as wave and wind conditions, and salinity observations have been carried out at the observation tower of Shirahama Oceanographic Observatory. In the summer in 2015, no typhoon approached around the observation site, and the high wave and strong wind conditions have not been captured during the observation. Several short-term rainfalls due to front and low pressure occurred, and it is reported that local areas in Shirahama town and neighboring towns suffered some damages with windblasts from late August to early September. It is found in the observation results of water temperature that the temporal variations of water temperature have a period of 3 to 6 days in the deeper layers like 20m deep and 30m deep. The cyclical fluctuation of water temperature at 30m deep has opposite phase to the fluctuation of salinity. This result means that low temperature and high salinity water approaches to the observation site periodically and that some influences of the water mass of the open sea exist.
  • TASHIRO KOKI, WATANABE YASUNORI, YAMADA TOMOHITO, OTSUKA JUN'ICHI, OYAMA TAKAHIRO  土木学会北海道支部論文報告集(CD-ROM)  (70)  ROMBUNNO.B-65  2014/02  [Not refereed][Not invited]
  • OYAMA TAKAHIRO, YAMADA TOMOHITO, WATANABE YASUNORI, OTSUKA JUN'ICHI  土木学会北海道支部論文報告集(CD-ROM)  (70)  ROMBUNNO.B-64  2014/02  [Not refereed][Not invited]
  • 小窪一毅, 中山恵介, 新谷哲也, 柿沼太郎, 大塚淳一, 渡部靖憲, 駒井克昭, 清水健司  土木学会北海道支部論文報告集(CD-ROM)  (70)  2014
  • 馬場 康之, 水谷 英朗, 久保 輝広, 内山 雄介, 森 信人, 渡部 靖憲, 山田 朋人, 猿渡 亜由未, 大塚 淳一, 二宮 順一  京都大学防災研究所年報  (58)  315  -320  2014  [Refereed][Not invited]
     
    This paper shows some results of a field observation carried out in the summer of 2014. The vertical profiles of currents and water temperature have been measured as well as wave and wind conditions, and salinity and dissolved oxygen level observations have been carried out at the observation tower of Shirahama Oceanographic Observatory. In the summer in 2014, a total of 4 typhoons (No.11, No.12, No.18 and No.19) approached to the Kii peninsula, and the high wave and strong wind conditons due to 2 typhoons (No.18 and No.19) have been captured during the observation. When the typhoons passed around the observation site, the high wave and strong wind occurred. However, the observation data of 2014 doesn't have clear shift of water temperature and salinity like the one by the typhoon No.18 in 2013. On the other hand, it is repeatedly found in the observed data that the reduction of water temperature and the increase of salinity happened simultaneously. This result indicates that the water temperature and the salinity around the observation site have some influence of the water mass of the open sea.
  • Hitoshi Gotoh, Akio Okayasu, Yasunori Watanabe  Computational Wave Dynamics  1  -234  2013/01/01  
    This book provides a comprehensive description of the latest theory-supported numerical technologies, as well as scientific and engineering applications for water surface waves. Its contents are crafted to cater to a step-by-step learning of computational wave dynamics and ocean wave modeling. It provides a comprehensive description from underlying theories of free-surface flows, to practical computational applications for coastal and ocean engineering on the basis of computational fluid dynamics (CFD). The text may be used as a textbook for advanced undergraduate students and graduate students to understand the theoretical background of wave computations, and the recent progress of computational techniques for free-surface and interfacial flows, such as Volume of Fluid (VOF), Constrained Interpolation Profile (CIP), Lagrangian Particle (SPH, MPS), Distinct Element (DEM) and Euler-Lagrange Hybrid Methods. It is also suitable for researchers and engineers who wish to apply CFD techniques to ocean modeling and practical coastal problems involving sediment transport, wave-structure interaction and surf zone flows.
  • Hitoshi Gotoh, Akio Okayasu, Yasunori Watanabe  Computational Wave Dynamics  v  -vii  2013/01/01
  • 馬場 康之, 水谷 英朗, 久保 輝広, 内山 雄介, 森 信人, 渡部 靖憲, 山田 朋人, 猿渡 亜由未, 大塚 淳一  京都大学防災研究所年報  (57)  455  -461  2013  [Refereed][Not invited]
     
    This paper shows some results of a field observation carried out in the summer of 2013. The vertical profiles of currents and water temperature have been measured as well as wave and wind conditions, and salinity and dissolved oxygen level observations have been carried out at the observation tower of Shirahama Oceanographic Observatory. During the observation, one typhoon (No.18, MAN-YI) approached to the Kii peninsula. When the typhoon passed around the observation site, the vertical mixing develops well, and water temperature at all measurement points show almost uniform distributions. It is also found during the typhoon passing that coastal upwelling through the Ekman transport happened clearly due to continuous southward wind. An EOF analysis decomposes the water temperature variation during the typhoon passing into 1) the increase and decease of water temperature and 2) the magnitude of the temperature difference in the vertical direction.
  • 渡部 靖憲  北海道地区自然災害科学資料センター報告  25-  (0)  3  -22  2012/03  [Refereed][Not invited]
  • 小窪一毅, 中山恵介, 新谷哲也, 丸谷靖幸, 岡田知也, 渡部靖憲  土木学会北海道支部論文報告集(CD-ROM)  (68)  2012
  • 小窪一毅, 中山恵介, 新谷哲也, 大塚淳一, 岡田知也, 渡部靖憲, 丸谷靖幸  土木学会年次学術講演会報告集  67-  II-055  2012  [Not refereed][Not invited]
  • 渡部靖憲  海と港  (29)  59  -67  2011/08/10  [Not refereed][Not invited]
  • 渡部 靖憲  可視化情報学会誌  31-  (1)  19  -22  2011  [Refereed][Not invited]
  • 強風下における微細飛沫生成・輸送過程の数値計算法の開発
    阿部伸弘, 猿渡亜由未, 渡部靖憲  論文報告集, 土木学会北海道支部  66-  B-46  2010  [Not refereed][Not invited]
  • OTSUKA Junichi, HIBATA Hazumi, WATANABE Yasunori  PROCEEDINGS OF COASTAL ENGINEERING, JSCE  54-  (54)  51  -55  2007  [Refereed][Not invited]
     
    In this study, distributions of dissolved CO2 under breaking waves are experimentally measured using two-color Laser Induced Fluorescence (LIF). CO2 mainly dissolves on gas/water interfaces of the plunging waves and around bubbles entrained by successive plunging jets. vortices induced by the jets quickly diffuse downward the dissolved CO2 together with the bubbles. Undertow transport the dissolved CO2 offshoreward below the trough level for enhancing the CO2 concentration in a whole surf zone.
  • SARUWATARI Ayumi, WATANABE Yasunori  PROCEEDINGS OF COASTAL ENGINEERING, JSCE  54-  (54)  66  -70  2007  [Refereed][Not invited]
     
    In this paper, a fragmentation model of jets with free-surfaces, describing evolution of the size spectra of sprays during the fragmentation process is developed. A 3-D large eddy simulation reproduces amplification of free-surface disturbances of the jets induced by the counter-rotating vortices and the resulting jetting flows splitting into fingers and sprays. It is found that a probability density of the finger or spray size can be described by a log-normal distribution, and its evolution depends on Weber number. The present fragmentation model is capable of predicting the volume fraction of the jets at arbitrary time after the inception of fragmentation.
  • OHSHIMA Kaori, MORIYA Yoichi, OTSUKA Junichi, WATANABE Yasunori  PROCEEDINGS OF COASTAL ENGINEERING, JSCE  54-  (54)  796  -800  2007  [Refereed][Not invited]
     
    Long-period waves are often trapped in a port and harbor, and cause disturbances of cargo handling and damages of mooring ropes for ships. A new type of long-period wave absorption structure which involves two oblique walls and a vertical slit between them has been developed for dissipate the waves. In this paper, through a large eddy computer simulation and visual experimental measurement, flow patterns and vortex structures formed with the proposing structure, depending on a relative structure length with incident wavelength, are investigated. The long-period waves are found to be reduced via a combination of energy exchanges to a pair of circulated flows trapped with in the structure and of energy dissipation due to turbulent jets formed at the slit.
  • 渡部 靖憲, 樫野 英之, 佐伯 浩  海岸工学論文集  51-  (51)  101  -105  2004  [Refereed][Not invited]
     
    この論文では, 粘性, 乱れを考慮した波動下の流速場の数値計算結果を回転, 非回転流れに分離し, 砕波に伴う非回転流速場から回転流速揚への遷移について調べられている.砕波点を境に非回転運動エネルギーの一部は回転運動エネルギーへと遷移し, さらに小スケール乱れへとエネルギーを受け渡す.回転流れ中の歪み率は非回転流れのそれより非常に強く乱れ生成と密接な関係をもつため, 乱れを適当に考慮した砕波モデルを考える場合にはこの回転流れの評価が重要になる.
  • 渡部 靖憲, 秀島 賢保, 佐伯 浩  海岸工学論文集  51-  (51)  106  -110  2004  [Refereed][Not invited]
     
    この論文は, 低計算コスト, 高精度, 高解像度で三次元粒子速度を取得可能な三次元Super-Resolution PIVを提案し, 計測精度及びその粒子数依存性を検証し工学的問題への適用性について議論するものである.また, 大規模渦モデルの速度場における本PIVシステムの解析と数値試験の解析解との比較を行い, その実践的適用性を検証すると共に, 砕波後に生成された大規模渦が海底砂を巻き上げる際に形成される混相乱流に対してもこのPIV法を適用し, 砕波通過後の流体, 固体両相の三次元速度分布の時間変化について議論される.
  • Watanabe Yasunori  Journal of the Visualization Society of Japan  22-  (1)  383  -384  2002  [Refereed][Not invited]
     
    Lagrangian fluid motion under breaking waves and settling motion of glass-particles released into a still water are measured by the 3D stereoscopic particle tracking velocimetry for a large domain (3DSPTV-LD). Since the 3DSPTV-LD dose not require to use a laser sheet for illuminating a single flow plane in a measur domain, it has an advantageous feature in engineering use -i.e. high applicability to 3D measurementsfor a large domain on less costs. In coastal engineering, the large-scale turbulence associated with a large-scale eddy structur, such as a separated vortex array around a structure, which futures three-dimensional behav-iora.is one of the crucial factors affecting sediment transport and stability of a structurc.The 3DSPTV-LD enables it to acquire the 3D large-scale Lagrangian motion over a wide area.
  • 渡部 靖憲, 山内 悠司, 佐伯 浩  海岸工学論文集  49-  (49)  106  -110  2002  [Refereed][Not invited]
     
    この論文は, 北海道石狩浜における現地実験 (2001.10.4) 及び室内実験を通して砕波帯に浮遊, 滞留する微細気泡量の岸沖分布を計測し, 水面の安定度に対する微細気泡生成の依存性を調べると共に, ハイドロフォンにより砕波下に発生した気泡音を受信することで, 気泡音の周波数解析を基本とした砕波後の生成気泡サイズ, 気泡数の時空間変化を特徴化し流体運動との関係を明らかにしようとするものである.さらに界面活性効果による気泡生成への依存性についても議論を行っている.
  • 加藤 雅也, 渡部 靖憲, 佐伯 浩  海岸工学論文集  49-  (49)  716  -720  2002  [Refereed][Not invited]
     
    ケーソン式混成堤の堤頭部では, 剥離を伴う複雑な三次元渦構造が形成されている. そのため, 堤頭部における被覆材の散乱は, 堤幹部における場合とは異なる複雑なメカニズムを有していると考えられる. 本研究では, 直立堤堤頭部周辺の流速場をLarge Eddy Simulationによりシミュレートし, 得られた水理量を用いて局所流体力特性の空間変動特性を調べた. その結果, 開口率の小さな中小規模港湾に対して現行設計法によりマウンド被覆材所要質量を算定した場合, 被覆材の質量が不足する可能性があることを示した. また, 堤頭部近傍では加速度の増幅効果によって, 慣性力の寄与が著しく大きくなる場合があることを明らかにした.
  • 渡部 靖憲, 松本 卓, 佐伯 浩  海岸工学論文集  49-  (49)  76  -80  2002  [Refereed][Not invited]
     
    この論文は, 二次元乱流波動境界層の三次元遷移と海底地形変動機構について論じるものである.三次元的海底地形の顕著な例であるbrick-pattern砂漣の形成の原因となる二次元砂漣上の流れの三次元不安定から発達する有意な三次元組織渦構造が三次元Large Eddy Simulationによって計算され, 海底面から放出されるpassive scalar関数の移流拡散過程が調べられている.移動床実験による海底形状と乱れ剪断力の二次元波数スペクトル解析が行われ, 卓越波数の相関について議論される.
  • 重松 孝昌, 渡部 靖憲, 竹原 幸生, 奥村 悠樹, 小池 敏也  海岸工学論文集  49-  (49)  806  -810  2002  [Refereed][Not invited]
     
    従来, 測定が困難であった多孔質構造物間隙内の三次元流体運動を計測するシステムの構築を行っている. 構造物と流体の屈折率を調整することにより, 物体背後の構造物および流体を視認することができ, さらに, 拡張型三次元ステレオグラムPTV流速計測システムを用いることにより, 間隙内流体運動の計測が可能になっている. 新たに中立粒子の開発も行っている. 構築したシステムを用いて, 波動場におけるテトラポッド潜堤の間隙流体運動の計測を行い, 三次元流速分布および乱れエネルギーの空間分布について考察している.
  • 渡部靖憲, 大塚淳一, 佐伯浩  海岸工学論文集  46-  (46)  116  -120  1999  [Refereed][Not invited]
  • 渡部靖憲, 安原幹雄, 佐伯浩  海岸工学論文集  46-  (46)  141  -145  1999  [Refereed][Not invited]
  • 渡部靖憲, WANG Y, 早川哲也, 佐伯浩  海岸工学論文集  46-  (46)  741  -745  1999  [Refereed][Not invited]
  • Watanabe Yasunori, Hosokawa Hiroki, Saeki Hiroshi  PROCEEDINGS OF CIVIL ENGINEERING IN THE OCEAN  11-  (11)  19  -24  1995  
    The phisical characterristics of breaking wave are investigated in cases of permitting to occur the return current and compulsorily removing it.Breaking wave motion is complicated by variety factors and connecting them.Effective one of these factors is return current which have a large scale effect compair with other factors as viscosity, capiraly stress, and turbulent. Therefore it is very important to investigate how the return current affect to the inner velocity field at breaking.Since the fluid motion is temporally and spacially unsteady in the breaking zoon, the messurement of fluid motion should be carry out in the view of these aspects.In this paper, the inner velocity at breaking is spacially investigated by perticle image velocimeter.Especially, we could understand that the structure of fluid motion is sufferd by the return current.
  • Okubo Yasuhiro, Watanabe Yasunori, Kioka Sinji, Saeki Hiroshi  PROCEEDINGS OF CIVIL ENGINEERING IN THE OCEAN  11-  (11)  283  -286  1995  
    Nowadays people enjoy a variety of sports and recreations on frozen surfaces in winter. It is important to estimate the bearing capacity of an infinite ice sheet in order to ensure their safety. In this study, (1) we show in charts and graphs the estimated bearing capacity of ice sheets obtained by the deflection of ice sheets per unit load without breaking the ice; (2) we obtain an equation to calculate the bearing capacity of ice sheets with holes and indicate the results in charts; and (3) we describe in charts the critical traveling speed of loads moving on ice sheet when the bearing capacity is at minimum.

Books etc

Presentations

Research Projects

  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2023/04 -2028/03 
    Author : 渡部 靖憲, 猿渡 亜由未, 新井田 靖郎, 二宮 順一, 馬場 康之, 大塚 淳一, 志村 智也, 内山 雄介, 森 信人
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2023/04 -2027/03 
    Author : 森 信人, 馬場 康之, 渡部 靖憲, 竹見 哲也, 二宮 順一, 志村 智也, 宮下 卓也, 豊田 将也, 福井 信気, 今井 優樹
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Fund for the Promotion of Joint International Research (Fostering Joint International Research (B))
    Date (from‐to) : 2022/10 -2026/03 
    Author : 渡部 靖憲
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
    Date (from‐to) : 2022/04 -2025/03 
    Author : 猿渡 亜由未, 渡部 靖憲
  • 日本学術振興会：科学研究費助成事業 国際共同研究加速基金(国際共同研究強化(B))
    Date (from‐to) : 2020/10 -2025/03 
    Author : 森 信人, 渡部 靖憲, 安田 誠宏, 中條 壮大, 下園 武範, 二宮 順一, 志村 智也, 宮下 卓也, 張 哲維
     
    本研究では，過去数百～数千年間に海中から移動し，陸域に打ち上げられた巨礫の移動限界とその分布について，北西太平洋を対象に国際共同調査・モデル開発を実施する．このため，近年および記録のない過去イベントで発生した巨礫の大きさ，物性，年代および沿岸地形について計測し，巨礫群の詳細な特性を把握する．第2に，巨礫の分布特性を説明可能な巨礫移動モデルを国際共同開発する．第3に，近年移動した巨礫の調査結果を元に，外力である沿岸域の暴波浪およびスーパー台風特性を逆推定する手法を開発し，最後に確率台風モデル等を組合せ，過去巨礫群を説明可能な1万年単位の最大級の暴波浪とスーパー台風の強度についての逆推定を実施する． 本年度は，近年の極端イベントにより移動が確認されている近代巨礫群の位置，3D形状，物性，陸上および海底地形の計測のための観測機器の整備およびその計測精度の確認を実施した．これと並行して，数値モデル開発を進め，質点移動として台風石の移動をリーフ上の流体力推定から生成，回転・並行移動を計算する数値巨礫移動モデルを開発した． 海外の共同研究では，Frediric Dias・ダブリン大学・教授およびAndrew Kennedy・ノートルダム大学・教授と巨礫発生・移動モデルの開発を進めた．Wen-Son Chiang・国立成功大学台南水理研究所・副所長とは，次年度以降の観測についての意見交換を行った．
  • 日本学術振興会：科学研究費助成事業 基盤研究(A)
    Date (from‐to) : 2019/04 -2023/03 
    Author : 森 信人, 渡部 靖憲, 竹見 哲也, 内山 雄介, 馬場 康之, 金 洙列, 志村 智也, 二宮 順一, 豊田 将也, 藤木 峻
     
    本年度は，波浪境界層を考慮して大気海洋境界過程のパラメタリゼーションの定量化・汎用化とこれを用いた沿岸災害等の数値モデルへの影響評価を実施し，最大クラスの高潮・高波想定，大気や海洋の循環場の高精度化を行った．具体的には，(A) 大気海洋境界過程の現地観測，(B) 大気海洋境界面の素過程の解明と定量化，(C) 高潮・高波・台風の極端現象，大気・海洋の循環場への影響評価の研究を実施した．各項目の実施内容は以下の通りである． 項目A 「大気海洋境界過程の現地観測」：大気海洋境界過程定量化のための詳細な大気・海洋の観測，パラメータ空間をカバーする広範囲のデータ収集・解析を実施した．項目Bにおけ る大気海洋境界面の素過程の解明・パラメタリゼーションのため，低～高風速，風波・うねりの状態等，広いパラメータ空間をカバーする現地観測データセットの整備を行った．このため，和歌山県白浜において大気・海洋観測塔を用いた観測を実施した． 項目B 「大気海洋境界面の素過程の解明と定量化」：運動量交換係数，熱交換係数，海面粗度，砕波乱流の4つのパラメタリゼーションにつながる素過程の理論構築を行った．海面境界過程を波浪境界層理論をもとに風速と波浪の方向スペクトルを説明変数として考え，運動量・熱交換係数，海面粗度高さについて理論的な枠組みの再構築を試みた．波浪方向スペクトルをもとに運動量・熱交換過程，鉛直代表長さスケールをパラメタライズする手法についても検討した． 項目C 「高潮・高波・台風の極端現象，大気・海洋の循環場への影響評価」：項目Bで得られたパラメタリゼーションを用い，高潮・高波・台風の極端現象，10年スケールの大気・海洋の大循環場等への影響について定量的に検討した．このため，現在の沿岸災害・環境評価の主軸の数値モデルである領域気象モデル，高潮モデル，波浪モデル，全球気候モデル，海洋モデルの開発を進めた．
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Research (Exploratory)
    Date (from‐to) : 2019/06 -2022/03 
    Author : Yasunori Watanabe
     
    A nonlinear wave model to estimate wave growth and maximum crest height of focussing wave groups was developed and validated with the experimental results. The shallow water wave focusing theory has been also extended to the one with wave-curent interactions. We found that the presence of opposing current significantly amplifies the focusing waves upto six times of the initial wave height, which depends on a wave spectrum of the initial wave group. We also performed physical and computational experiments to simulate planar focusing wave groups, and found that possible effects of nonlinear energy transfers among crossing waves and flip-through phenomenon caused by the crossing wave impacts to further growth of focussing waves expected in a coastal region.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2019/04 -2022/03 
    Author : IZUMI Norihiro
     
    We investigated the physical processes of submarine landslides triggered by earthquakes and the resulting tsunami and turbidity currents from the viewpoints of laboratory experiments, theoretical analysis, and numerical simulations. We studied the movement of turbidity currents by solving the layer-averaged momentum equations, continuity equation, and the transport equation of suspended sediment of turbidity currents numerically. The results show that the transition from a landslide to a turbidity current that can travel long distances does not depend on the initial suspended sediment concentration or velocity unless the initial Richardson number is greater than unity. We developed numerical simulation models to reproduce tsunamis caused by a submarine landslide and those generated by the superposition of tsunamis generated by a submarine landslide and an active fault.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
    Date (from‐to) : 2018/04 -2022/03 
    Author : Yasunori Watanabe
     
    We developed computational models to simulate turbulence transitions over waves, formations of thermal boundary layers, and bubble-mediated turbulent flows, which provides physical mechanims contributing to sea-surface drag forces and momentum transfers between atmosphere and ocean. In wind tunnel experiemnts, for the first, we succesfully measured size spectra of the both of sea spray dispersed in atmosphere and air bubbles entrained into sea owing to wind wave breaking, which is related to the sea surface drag and bulk parameters. Contributions of gas dissolution from the entrained bubbles to air-sea gas exchages have been identified through physical and computational experiments. A new model of bubble drag in bubble clouds was also developed in this project, contributing physical understanding of wave-induced aeration process. In ocean observation, features of sea spray, bubble entrainment due to wind wave breaking, and their contributions to heat transfers across sea surfaces.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Research (Exploratory)
    Date (from‐to) : 2018/06 -2021/03 
    Author : Mori Nobuhito
     
    In recent years, there are many researches on the distribution of large coastal boulders that have moved from the sea and run-up on land. We attempted to estimate the wave forces and related typhoon intensity from the observed distribution of typhoon boulders. In order to estimate the boulder movement by numerical models, we conducted hydraulic model experiments of boulder movement for solitary waves simulating tsunami and irregular waves simulating typhoon waves. In the case of solitary waves, the distance traveled by boulders was larger when the horizontal bed was dried out, and in the case of irregular waves, when the bed was submerged. In addition, a numerical model of the boulder movement phenomenon was developed, and its range of application and model optimization were carried out using the results of hydraulic experiments. Good results were obtained for the distance of boulder movement by solitary wave and irregular wave.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Research (Pioneering)
    Date (from‐to) : 2018/06 -2021/03 
    Author : Kimura Katsuki
     
    Organic matter in municipal wastewater can be recovered and concentrated by using direct membrane filtration (DMF) adequately, which leads to net-generation of energy from wastewater. Flat-sheet ceramic membranes are physically and chemically robust, and therefore intensive membrane cleanings that cannot be used with polymeric membranes can be used. In this study, DMF of municipal wastewater by flat-sheet ceramic membranes was investigated. With the aid of intensive physical and chemical cleaning, long-term operations under high membrane fluxes were possible. In addition, switching the feed from of the influent of the primary sedimentation basin to the effluent, very short-period aeration, alternative use of acid and oxidant in chemically enhanced backwash were found to be effective for mitigation of membrane fouling in DMF.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
    Date (from‐to) : 2015/04 -2020/03 
    Author : Shimizu Yasuyuki
     
    This study systematizes a wide range of knowledge about the long-term dynamics of meandering, and builds the basic technology for realizing river development that makes full use of natural power and individuality. In particular, focusing on the meandering that determines the plane alignment of river topography, we deeply consider the fundamental mechanism of both short-term fluctuations due to sudden disasters and long-term topographical changes from past to future, and clarified the phenomena. In addition, we analyzed the various impacts on meandering, such as vegetation, presence of estuaries and river structures, diversity of meteorological and topographical geological conditions by theoretical analysis, field surveys, and simplified physical experiments. We also have constructed a computational model that can predict the meandering development transition considering various hydraulic conditions.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2015/04 -2018/03 
    Author : Mori Nobuhito, KENNEDY Andrew
     
    A earthquake tsunami occurs is along the plate boundary but they are co-exists tropical cyclone active regions in the tropical to mid-latitudes. In the case of Okinawa, clear overlapping of tsunami and typhoon induced boulders, and therefore understanding coastal boulder characteristics by tsunamis and tropical cyclone waves is important to know. In this study, the distribution of coastal boulders transported from the ocean to land were survey in the Pacific Rim and the Caribbean Ocean. It can evaluate the historic gigantic tsunami and typhoons, potentially. The main objective is to conduct extensive and detailed field investigations on the size, position, physical properties and coastal topography of tropical coast. Based on the results of survey, the distributions and characteristics of boulders in the Pacific Rim and the Caribbean Sea will be summarized for the estimation of magnitude historical of events of tsunami and tropical cyclones.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2015 -2018 
    Author : Yasunori Watanabe
     
    We found fundamental features of heat and gas transport in aerated ocean surface layers and modifications of surface drag in violent wave field through experimental parameterization of effects of sea sprays and bubbles entrained by wind wave breaking, computational identifications of heat and gas transfer owing to surface replacement under breaking waves, variable features of surface drag depending on transitions of three-dimensional vortex structures over ocean waves. As sea sprays dispersed in wind boundary layers disrupt the organization of the vortices formed over the breaking waves, causing transitions to fully developed turbulent boundary layer and modifications of surface drag. This process also changes the total momentum and heat fluxes between atmosphere and ocean.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2013/04 -2017/03 
    Author : Kimura Ichiro
     
    To enable a large-scale river planning considered connections of whole river basin, we developed novel numerical and mathematical tools, and checked their validity by applying them to flood events with different temporal and spatial scales. The tools are composed of flood physics model, flood economic model and flood evacuation model. The flood physics model is the most fundamental part for the river planning, and is divided into 4 components, the large-scale inundation model, inner-outer inundation connected model, flood induced local flow model and tsunami model. Those tools were tested through the applications to past flood events with different scales, and the results were compared with observations. Such calibration process showed that the river planning aided by the proposed new tools are quite useful and practical. Some components of the results were assembled as free-software on an open-source platform to enable everyone in the world can use our result without limitations.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research
    Date (from‐to) : 2015 -2017 
    Author : Watanabe Yasunori
     
    This study provided a novel mechanical model imposed at a toe of tsunami running up over arbitrary ground conditions. This model has been confirmed to provide appropriate dynamic responses of the run-up waves and to estimate accurate flood areas. The specific research achievements are; (1)improvements of the imaging technique to measure dynamic three-dimensional water surfaces, (2) introduction of a phase-field model to three-dimensional fluid flow computations, (3) validations of the proposed model, and (4) establishing new computational framework for run-up tsunami computations. The proposed model has been applied to the two practical cases of tsunami floods, in urban area and river basin, observed in the 2011 Tohoku earthquake tsunami, which provided distinctive flooding processes depending on the ground conditions.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2012/04 -2015/03 
    Author : YOKOTA Hiroshi, WATANABE Yasunori, SATO Yasuhiko, KATO Ema, HASHIMOTO Katsufumi
     
    This research focused on how the comprehensive damage grading system is established for a long un-reinforced concrete structure along coastlines from the viewpoints of structural performance and functions of disaster prevention. Major damage induced in this type of structure is concrete cracking due to shrinkage of concrete and differential settlement of the structural body; accordingly, crack width, depth and position are categorized and modeled into the structural analysis tool. Moreover, shear transfer behavior between the crack surfaces was experimentally made clear. Finally, structural analysis taking into account the above behavior was carried out to quantify remaining structural performance of damaged structures. In conclusion, new criteria for damage evaluation have been proposed to access the function and performance of cracked un-reinforced concrete structures. These results may contribute to realize more effective and objective maintenance work.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
    Date (from‐to) : 2011/04 -2015/03 
    Author : MASE Hajime, HASHIMOTO Noriaki, YAMADA Fumihiko, YOKOKI Hiromune, KUROIWA Masamitsu, NOGUCHI Kenji, KAWAI Hiroyasu, KITANO Toshikazu, MORI Nobuhito, WATANABE Yasunori, TAKEMI Tetsuya, YASUDA Tomohiro, OKU Yuichiro
     
    Projection of typhoons, storm surges and waves were conducted for impact assessment of coastal environment in the future. The observed sea level rise was analyzed based on the satellite observation and is 3 mm/year around Japan. Future changes of tropical cyclone activity was analyzed based on CMIP3 and CMIP5 results. The cyclogenesis number will be decreased and the tracks will be shifted to Eastward at the Northwest Pacific Ocean in the future. Risk of storm surge is estimated targeting Ise-wan (Vera) typhoon. The maximum level of storm surge and related uncertainty is discussed. The impact of coastal morphology was examined and shore line change based on standard sea level rise analysis is not sufficient for dynamic behavior of beach morphology.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research
    Date (from‐to) : 2012 -2014 
    Author : WATANABE Yasunori
     
    A novel imaging system to measure three-dimensional surface shapes, based on the projector-camera system, was improved with aim to extend the practical applicability to coastal and hydraulic engineering. The additional algorisms to synchronize the projector and digital camera and to dynamically track the color patterns reflected on the surfaces were developed and introduced to the measurement system. The additional improvement for reducing optical errors associated with Lambert multiple dispersion system formed in liquid was also introduced to the system. The developed measurement system was applied to experimental breaking waves to examine the reliability and capability to measure dynamic deformation of the free-surface. The measured results provided new aspects of the physical evaluation of transient free-surface forms of breaking waves.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2012 -2014 
    Author : WATANABE Yasunori, YAMADA Tomohito, MORI Nobuhito, OTSUKA Junichi
     
    A novel numerical simulator to compute local behaviors of sea sprays and entrained bubbles produced by micro ocean wave-breaking processes, based on the stochastic turbulence model, was developed in this study. The model was confirmed to reasonably reproduce heat and gas transfer through advection and diffusions processes via gas-liquid mechanical interactions. Physical experiments for measuring the size distributions of sea-sprays and bubbles entrained into sea and the thermal radiation on the breaking-waves faces were performed in a wind wave flume. The momentum and heat transfer on the aerated ocean waves were found to be parametrized by the wind wave Reynolds number.The in-situ measurements for sea-sprays and air bubbles in ocean were also performed for characterizing mechanical contributions of the aerated ocean surface to the wave and current field.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2009 -2011 
    Author : GOTOH Hitoshi, OKAYASU Akio, HIRAISHI Tetsuya, SHIGEMATSU Takaaki, KAWASAKI Koji, MUTSUDA Hidemi, WATANABE Yasunori, MORI Nobuhito, HARADA Eiji, HIRAYAMA Katsuya, KHAYYER Abbas, IKARI Hiroyuki
     
    In this study,' Numerical Wave Flume' for a resilient design of coastal structures against violent waves was constructed by introducing free-surface flow models, including particle method. The characteristic of numerical models were investigated by 4 types of benchmark tests. And GPGPU computing was introduced tomake calculation as fast as possible. One of the tsunami disasters in the Tohoku-Pacific Ocean Earthquake was simulated by' Numerical Wave Flume' to examine its applicability
  • Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(挑戦的萌芽研究)
    Date (from‐to) : 2009 -2011 
    Author : Yasunori WATANABE
     
    The dinoflagellate Pyrocystis lunula emits light in response to water motion. The statistical features of the bioluminescence, emitted by P. lunula, owing to dynamic impact pressure and shear stress in oscillatory boundary layer flows over ripped bed were studied with the aim to develop a new imaging technique for measuring fluid stresses, pressure and shear, using plankton that emit light in response to mechanical stimulation. Since the flash intensity correlated with the both impact pressure and fluid strain rate, the instantaneous planar distribution of the fluid stresses can be estimated from video images of the bioluminescence in a fluid region by using the empirical relation determined in this study.
  • Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(A))
    Date (from‐to) : 2007 -2010 
    Author : Yasuyuki SHIMIZU, Norihiro IZUMI, Yasunori WATANABE, Hirofumi TAKEBAYASHI, Yasuharu WATANABE, Hiroyasu YASUDA
     
    This research presents numerical and analytical models describing sediment transport occurring at wide-ranging scales in flooding river flows ; local sand-laden turbulent flow, river-bed evolution at meandering length scale, morphological effects of permeable groundwater, and responses of flood to multiple-scaled watersheds.
  • Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(C))
    Date (from‐to) : 2007 -2008 
    Author : Nobuhito MORI, 渡部 靖憲, Yasunori WATANABE, Kousei TAKEHARA
     
    沿岸域の砕波帯などで見られる水面波の砕波は, 時空間的に非定常かつ高速にマイクロスケールからセンチメートルスケールに渡る大きさの気泡や飛沫を多数発生させる. このような砕波により生成される気泡および飛沫を計測する手法を開発した. これを用いて, 砕波帯における気泡の計測を行い, 沿岸部における気泡の大きさや個数について調べ, 波浪条件との関係を明らかにした.
  • Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(若手研究(B))
    Date (from‐to) : 2006 -2008 
    Author : Yasunori WATANABE
     
    沿岸域の波浪の砕波に伴い大量の空気が海中に混入すると共に空気中には飛抹が放出され、複雑な空気と海水が混合した乱流が発達する。この状態で波浪が海岸構造物に衝突するとき気体と液体との相互の作用から非常に強い衝撃力が発生し、被災の主要な原因となる。この衝撃力とエアレーションとの関係を最新の計測技術と計算技術によって定量化し、モデル化を行ないその信頼性と実用性を検証した。
  • Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(B))
    Date (from‐to) : 2004 -2006 
    Author : Yasuyuki SHIMIZU, 渡邊 康玄, 泉 典洋, 竹林 洋史, 渡部 靖憲
     
    A weakly nonlinear analysis considering the interference between alternate bar and double-row bar has been developed. Findings show that when the two modes are on the same order, the mode cross interference controls development process of each wave and they cannot grow simultaneously. The development process of bars is strongly influenced of the mode cross interference. Hydraulic experiments and the weakly nonlinear analysis, by setting several hydraulic conditions under which either alternate bars or double-row bars formed, have been conducted to clarify a changing process of bar shape for...
  • 文部科学省：科学研究費補助金(若手研究(B))
    Date (from‐to) : 2003 -2005 
    Author : 渡部 靖憲
     
    ・砕波が混入する気泡の砕波乱流への統計的寄与を明らかにするため,気液両相の速度の同時画像計測法を開発し,高解像計測を行った.この同時計測は,2つのデジタルビデオカメラに透過波数の異なる光学フィルターを設置し,蛍光着色した中立粒子と混入気泡にレーザー照射したそれぞれ励起光,反射光を選択的に記録し,Particle imaging velocimetryにより両相の速度分布を算定することで達成できる.この計測法の信頼性は,Ultrasonic Velocity Profilerとの比較によって検証された.気泡の混入が流体の乱流生成に統計的に大きな影響を与えると共に,気相の平均速度は流体の減速位相において流速の50%程度早い速度をもつ.これらの定量的に得られた統計量は砕波乱流のモデル化に使われる.・同一の画像計測法を底面砂の浮遊現象へ適用し,移動床上の浮遊イベント時の砂-流体相互作用の統計評価を行った.流体は底面近傍で上方へ向かう流れが卓越するが,砂はこれに追従せず形成されるリップルのクレスト方向へ移動する傾向がある.すなわち,浮遊砂は流体に対してパッシブな挙動をとらない.また,移動床上では,固定床と比べ境界層の剥離による力学的な影響が小さく,砂の浮遊に伴う流体の撹乱が乱れの生成の主要な役割を果たしていることが明らかになった.また,砂の浮遊にはこの撹乱に伴い強化された渦の再付着が大きくかかわっている.・砕波後のジェットの着水が生成する飛沫及び気泡を再現する数値モデルを開発した.これは,デカルト座標系上で自由水面での力学的境界条件を合理的に満足させ水面流速を適切に近似するものであり,正しく水面,渦そして表面張力による相互作用を評価するものである.このモデルにより,ジェットの着水に伴う二次ジェットの分裂及び局所的なキャビティーを再現し,砕波乱流のソースとなる水面の極近傍の渦生成を評価することが可能となった.
  • Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(B))
    Date (from‐to) : 2003 -2005 
    Author : Takaaki SHIGEMATSU, 渡部 靖憲, 竹原 幸生
     
    The aim of this study is to develop a measurement technique for understanding three dimensional turbulence structures in liquid-solid flows. This study is composed of two processes ; one is for improvement of Super Resolution PIV developed by Takehara on time resolution and the other is for improvement of 3-D stereo PIV developed by Watanabe on space resolution.Although the super resolution PIV can measure the flow field with high space resolution by using many particle tracers for visualization, it did not have enough time resolution because we did not have enough capturing system. This pr...
  • Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(B))
    Date (from‐to) : 2003 -2004 
    Author : Hiroshi SAEKI, 渡部 靖憲
     
    We developed a simulation method of Ice Scour Event considering probability distributions of various environmental parameters. As a result of calculations made under various conditions, order similar to those in the field observation data -the scour length of several tens of meters to several kilometers and the scour depth of several tens of centimeters to several meters -were found. Furthermore, due to the similarity to (reproducibility of) the comprehensive tendency/property of actual scour events, results that compared favorably with field observation results were obtained. Using the sim...
  • Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(A))
    Date (from‐to) : 1999 -2002 
    Author : Hiroshi SAEKI, 橘 治国, 渡部 靖憲
     
    In this research project, we obtained the following results :a) The coefficient of shearing force separated form the component of form drag force is obtained. In the case of ice jam, the form drag force can be ignored when l/H (l : length of ice floes, H : ice thickness) is mare than 450 because it is lero than 1% of the shearing force.b) Through the observation at Saroma lagoon, when ice floes are completely trapped in the ice boom, apart of the fluid force acting on the ice floes is transmitted via the ice floes to the ice boom, and the remainder of the fluid force due to arching of the i...
  • 文部科学省：科学研究費補助金(奨励研究(A))
    Date (from‐to) : 2000 -2001 
    Author : 渡部 靖憲
     
    本年度は、以下の研究を明らかにした。砕波ジェットのモデルとして貯水パイプにためられた水塊を瞬時に落下させ、水塊の水面への衝突に伴う混入気泡径及び発生から分裂さらに浮上にいたる気泡発達過程を評価する新たな解析法を開発した。気泡生成時に放射される音波をハイドロホンにより計測しウェーブレットパケット変換によりその発達過程を通じた気泡径を推算することによって発生する気泡はウェーバー数とフルード数によって5つの典型的なタイプに特徴化することができる。水中音を元にした計測法を多量の気泡が発生する実際の砕波に適用した。砕波フロントの到着直後、着水点の前後及びbubble clouds到達後で完全に異なる周波数帯の気泡音が確認された。砕波の局所的な流体運動に生成気泡の特性が大きく依存することが明らかになった。また、現地観測及び室内において生成微細気泡量の計測が行われ、実海域の気泡量が淡水を用いた室内実験より大きな値を示し、特にsawash zoneで急激な上昇が存在することが明らかになった。界面ステートに対する生成気泡の差異を界面活性剤を淡水中に混入させ室内実験を実行した。これにより安定した界面に発生する気泡は平均で非常に小さく、砕波形態に大きく依存することが明らかになった。上述の実験及び現地観測の結果により、砕波後の気泡の発達過程と気泡径について詳細な情報を得ることができた。これらの結果は、砕波後の気液二相流としての数値気泡モデルの定数を決定し気泡流計算を実行するために有効な情報である。
  • 文部科学省：科学研究費補助金(奨励研究(A))
    Date (from‐to) : 1998 -1999 
    Author : 渡部 靖憲
     
    砕波帯内の3次元流速場・水粒子軌道の特性について,以下の重要な結論が得られた.1.中立粒子運動の3次元ビデオ解析・砕波時の混入気泡の影響を低減するため中立粒子に蛍光塗料を塗布しブラックライトを照射しビデオカメラを2次元水槽の上面及び側面からから撮影する3次元水粒子追跡実験方法を提案した.・統計解析及びwavelet解析により,砕波時にはほぼ2次元的であった流体運動が砕波過程を通して3次元性が強化され,2次元的な運動エネルギーが徐々にスケールダウンすることが明らかになった.・同様な解析により,水平及び鉛直方向に方向性をもつエネルギーが水深が浅くなるにつれ方向性を失うことが明らかになった.2.3次元Large Eddy Simulation・低レイノルズ数補正を行った高精度数値計算法を適用したLarge Eddy Simulationにより初めて砕波後の3次元流速場の数値的再現に成功した.・砕波ジェット着水直後に水平ローラー渦だけでなく縦渦及び旋回渦が生成されることが明らかになった.・生成された大規模渦整構造は,ボア領域において崩れ,発達した乱流に遷移する.この渦は戻り流れによって沖側に移流され次の砕波の3次元流速構造に大きな影響を与える.・砕波点近傍に移流された渦塊は連続する砕波に影響を与え,流速場及び水面形の3次元化を促進させる.この渦塊は砕波が繰り返されると共に強化されるので,徐々にジェットの着水以前に水面形が3次元化する.・計算領域にマーカーを配置し移流させることによって水粒子を追跡した.砕波フロント背後において斜め後方に軸を持つ渦を発見した.この渦は過去に実験的に気泡追跡によってのみ確認されている斜行渦の軌道と酷似しており,我々の発見した渦は斜行渦であると特定した.3.ビデオ解析による流体運動の3次元性に関する実験及び現地観測・実験水槽及び現地に水中カメラを固定し,混入気泡の映像から流体運動の3次元性を調べた.波の進行と直角方向に不規則な間隔で発生する発達した雲状の気泡が確認された.

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