研究者データベース

渡部 靖憲(ワタナベ ヤスノリ)
工学研究院 土木工学部門 自然災害適応
教授

基本情報

所属

  • 工学研究院 土木工学部門 自然災害適応

職名

  • 教授

学位

  • 博士(工学)(北海道大学)

ホームページURL

J-Global ID

研究キーワード

  • 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   

研究分野

  • 社会基盤(土木・建築・防災) / 水工学

職歴

  • 2008年 - 2012年 北海道大学 工学(系)研究科(研究院) 准教授

研究活動情報

論文

  • Yasunori Watanabe, Yosuke Tsuda, Ayumi Saruwatari
    Coastal Engineering Journal 62 2 336 - 349 2020年04月02日 [査読有り][通常論文]
  • A. Saruwatari, K. Fukuhara, Y. Watanabe
    Coastal Engineering Journal 61 4 520 - 534 2019年10月02日 [査読有り][通常論文]
     
    © 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.
  • 猿渡 亜由未, 石見 翔汰, 渡部 靖憲
    土木学会論文集A2(応用力学) 75 2 I_531 - I_537 公益社団法人 土木学会 2019年 [査読有り][通常論文]
     

    気泡バースティングにより生成される微細飛沫発生量は海洋性エアロゾルの供給量を決定する重要なファクターであるにも関わらず,エアロゾル観測の困難さから未だそれを精度よく予測する為のモデルは提案されていない.本研究では空気負イオン濃度観測が海洋飛沫観測精度の向上に寄与し得るかどうかを検討する為の基礎的な検討材料を得る為の室内実験及び現地観測を行った.室内実験では気泡バースティングに応答した周囲の空気負イオン濃度の変化の特徴を明らかにした.また現地観測ではこれまでに飛沫発生量予測のモデルパラメータとして用いられてきた風速,波高,泡沫占有率と空気負イオン濃度との関係について調査し,特に気泡バースティングにより飛沫発生量を直接支配すると考えられる泡沫占有率が空気負イオン濃度の変化を最もよく記述することが明らかになった.

  • 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 Journal of Japan Society of Civil Engineers. 土木学会海岸工学委員会 編 75 2 I_49 - 54 土木学会 2019年 [査読有り][通常論文]
  • 髙木 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 Journal of Japan Society of Civil Engineers. 土木学会海岸工学委員会 編 75 2 I_61 - 66 土木学会 2019年 [査読有り][通常論文]
  • 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 Journal of Japan Society of Civil Engineers. 土木学会海岸工学委員会 編 75 2 I_67 - 72 土木学会 2019年 [査読有り][通常論文]
  • 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 75 2 I_271 - 276 土木学会 2019年 [査読有り][通常論文]
  • 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
    地球環境研究論文集 : 地球環境シンポジウム 27 41 - 46 土木学会 2019年 [査読有り][通常論文]
  • Yuta Mitobe, Hitoshi Tanaka, Kazuya Watanabe, Neetu Tiwari, Yasunori Watanabe
    Coastal Engineering Journal 60 4 516 - 531 2018年10月02日 [査読有り][通常論文]
     
    © 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 2018年10月01日 [査読有り][通常論文]
     
    © 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年09月01日 [査読有り][通常論文]
     
    © 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).
  • Yasunori Watanabe, Yuta Mitobe, Hitoshi Tanaka, Kazuya Watanabe
    Proceedings of the Coastal Engineering Conference 36 2018 2018年 [査読有り][通常論文]
  • Junichi Otsuka, Yasunori Watanabe
    Proceedings of the Coastal Engineering Conference 36 2018 2018年 [査読有り][通常論文]
  • 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) 74 2 I_661 - I_666 公益社団法人 土木学会 2018年 [査読有り][通常論文]
  • Turbulent Boundary Layer Flows over Progressive Water Waves
    K. Yamashita, Y. Watanabe, A. Saruwatari
    Proc. iCFM 2018年 [査読無し][通常論文]
  • Phase-Field computation of drop impacts
    S. Kadowaki, Y. Watanabe, A. Saruwatari
    Proc. iCFM 2018年 [査読無し][通常論文]
  • Ayumi Saruwatari, Junichi Otsuka, Yasunori Watanabe
    Proceedings of the Coastal Engineering Conference 36 2018 2018年 [査読有り][通常論文]
  • 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 74 2 I_667 - 672 土木学会 2018年 [査読無し][通常論文]
  • 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 74 2 I_67 - 72 土木学会 2018年 [査読無し][通常論文]
  • Mitobe Yuta, Tanaka Hitoshi, Watanabe Kazuya, Tiwari Neetu, Watanabe Yasunori
    COASTAL ENGINEERING JOURNAL 60 4 516 - 531 2018年 [査読有り][通常論文]
  • Junichi Otsuka, Ayumi Saruwatari, Yasunori Watanabe
    Advances in Water Resources 110 59 - 76 2017年12月 [査読有り][通常論文]
     
    © 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 2017年12月 [査読有り][通常論文]
     
    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.
  • 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 33 229 - 234 北海道開発技術センター 2017年 [査読無し][通常論文]
  • 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) 73 2 I_973 - I_978 公益社団法人 土木学会 2017年 [査読有り][通常論文]
     
    最も基本的な構造体である平板を中心とする様々な規模の角柱を対象とした海氷の衝突実験ならびにDEMによる数値実験を実施した.均一な物性・強度の氷やその完全な面接触など理想条件での衝突が現実では極めて困難または稀であり,必然的に実験結果がバラつく事,その衝突波形や破壊機構が複雑である事,等を数値実験から説明した.実験値及び実験困難な様々な条件での数値実験結果は,破壊の有無,動弾性率,衝突速度,氷の規模等に関わらず,理論的に得た弾性体の平板への最大衝突力を推定する単純な式の傾向特性と一致した.その理論式をベースとし,高速で漂流する小規模氷塊が脆性破壊を伴って衝突する場合の,平板を含む任意サイズの角柱構造物への最大衝突力を簡便に評価する方法の提案を試みた.
  • 渡部 靖憲, 杉村 一直
    土木学会論文集B2(海岸工学) 73 2 I_73 - I_78 公益社団法人 土木学会 2017年 [査読有り][通常論文]
     
    本研究は,風洞可視化実験から,風波の発生,成長過程における波浪下の流速分布の遷移,乱流統計量の変化を基に,非平衡風波場における運動量,エネルギー輸送機構を議論するものである.初期波において毛管波の重畳と重力波のクレストへの集中が顕著な渦生成を誘発し,大気境界層と同等の運動量境界層の形成を通して運動量,エネルギーを深い位置まで輸送する.フェッチの増大と共に,吹送流による波-流れ相互作用は重力波前面を先行して伝播する毛管波を減衰させ,渦供給の減少,運動量境界層の減衰を引き起こし,吹送流が主体となるせん断流が流れ場を支配する.
  • 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) 73 2 I_829 - I_834 公益社団法人 土木学会 2017年 [査読有り][通常論文]
     
    苫前漁港は,北海道日本海側に位置する第3種漁港である.本漁港は季節風の影響を受ける海域特性から,特に冬季において西外護岸における越波が激しく,同護岸背後の漁港利用や漁船の係留に支障をきたしている状況にある.しかしながら,現地では,越波の発生形態(越波高や飛散距離)や越波発生時の外力条件について未解明な状況である.そこで,本研究では,西外護岸における越波現象を把握するため,Webカメラを用いた現地観測を行うとともに,Webカメラが捉えた越波事象に対し,波浪・風況及び潮位等の外力条件との関係性を種々分析した.さらに,現地に適応可能な数値波動水路モデル(CADMAS-SURF)を構築して補足的な数値実験を加えることによって,現地の越波発生特性を解明した.
  • 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) 73 2 I_205 - I_210 公益社団法人 土木学会 2017年 [査読有り][通常論文]
     
    2016年台風10号は従来と異なる複雑な経路をたどり,東北地方を北西に移動し,日本海へと進行した.この台風により北海道内浦湾では高潮が発生し,台風による吹送流と強風により大きな漁業被害をうけた.このような前例のない経路を辿った台風での検討は重要である.そこで,本研究では,台風モデルと非線形長波モデルを使用した高潮計算を行った.本台風をモデルとし,想定されうる8コースで高潮計算を行い,内浦湾での潮位偏差の発生特性を解明するとともに,危険に作用する経路を推測した.さらに,『高潮浸水想定区域図作成の手引き(国土交通省)』に基づく,想定台風による試算を行い,今後の内浦湾沿岸での浸水想定における知見を得た.
  • 渡部 靖憲, 鈴木 敦貴
    土木学会論文集B2(海岸工学) 73 2 I_91 - I_96 公益社団法人 土木学会 2017年 [査読有り][通常論文]
     
    砕波過程において生じるエアチューブの軸方向分裂を模擬する気液を封入した水平回転円筒実験を行い,回転数,円筒幾何形状,封入水体積率に応じて変化するエアチューブの分裂現象を発見し,パラメータ化を通して,その分裂メカニズムを議論した.実験を通して,回転流体中の遠心力に加え,表面張力,浮力(重力)そして抗力が非一様な流れを形成することで発生する流れの不安定が分裂過程を決定することが証明された.エアチューブの分裂形態のおおよその特徴はFroude数で与えられ,軸方向に一様な水層の気体セルへの分裂の開始は限界Froude数及び限界Weber数で決定できる.これら回転円筒内の流れの特徴は砕波形態及び規模の異なるエアチューブの崩壊過程に内在する基本メカニズムになるものと考える.
  • 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年11月22日 [査読有り][招待有り]
  • 渡部靖憲, 田中 仁, 三戸部佑太, 渡辺一也
    土木学会論文集B2(海岸工学) B2-72 I_283 - I_288 2016年11月17日 [査読有り][通常論文]
  • 三戸部佑太, 渡辺一也, 田中 仁, Neetu Tiwari, 渡部靖憲
    土木学会論文集B2(海岸工学) B2-72 I_259 - I_264 2016年11月17日 [査読有り][通常論文]
  • 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) 72 2 I_493 - I_498 土木学会 = Japan Society of Civil Engineers 2016年11月15日 [査読有り][通常論文]
     
    金沢大学理工研究域環境デザイン学系半閉鎖性内湾である和歌山県田辺湾湾口部において,ADCP,塩分水温計などを用いた長期連続観測を行い,主に流動構造と海水交換特性に関する解析を行った.クロススペクトル解析結果から,流速鉛直構造と外力との対応については,表層付近の日周期変動には海上風が,成層期の混合層下部の半日周期変動には内部潮汐が,成層崩壊期の混合層全層では半日周期潮汐がそれぞれ寄与していることが分かった.一方,海水交換に対しては半日周期潮汐変動が最も寄与しているのに対し,それと同程度に周期約3日にピークを有するサブタイダル長周期成分の影響が大きかった.この長周期変動は紀伊水道スケールで生じる地形性のメソスケール渦の消長と密接に関係しており,モデルによる先行研究と整合的であった.出版者照会後に全文公開
  • 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) 72 2 I_487 - I_492 土木学会 = Japan Society of Civil Engineers 2016年11月15日 [査読有り][通常論文]
     
    金沢大学理工研究域環境デザイン学系台風イベント時の水温躍層の破壊・再形成のプロセスに着目して,観測データの解析を行うことでプロセスの経過について検討した.水温躍層は水域内の流動に大きな影響を与え,水質問題が生じる要因にもなるため,詳細な現象の把握が求められている.そこで本研究では,台風イベント時の観測データからブラント・バイサラ振動数およびリチャードソン数を算出し,成層の安定性を評価した.その結果,密度成層期には,まず高波浪により成層の安定が崩され強風により更に不安定さが促進されるという仮説を得た.また,混合期は成層が不安定で,台風接近前からシア流の不安定が生じていて混合が生じていることがわかった.これらの結果を踏まえて,更にTS図を作成し混合期の水塊の特性を評価した.出版者照会後に全文公開
  • 三戸部佑太, Neetu Tiwari, 渡辺一也, 田中 仁, 渡部靖憲
    土木学会論文集B2(海岸工学) B2-72 I_259 - I_264 2016年11月 [査読有り][通常論文]
  • Y. Watanabe, D. M. Ingram
    Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 472 2194 20160423  2016年10月01日 [査読有り][通常論文]
     
    © 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 2016年07月01日 [査読有り][通常論文]
     
    © 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年02月20日 [査読無し][通常論文]
  • 猿渡 亜由未, 武江 寿大, 渡部 靖憲
    土木学会論文集B2(海岸工学) 72 2 I_247 - I_252 公益社団法人 土木学会 2016年 [査読有り][通常論文]
     
    発生頻度の増加が指摘されている冬季の爆弾低気圧は,2014,2015年に相次いで根室で高潮被害をもたらすなど,台風とは異なる新たな高潮外力として対策が求められている.本研究では根室湾付近を通過する冬季の温帯低気圧による高潮リスクを,アンサンブル気象場による高潮発達過程の三次元数値計算結果を基に,統計的に評価する.高潮発達過程における湾内の流れ場は,海上風と湾奥方向への水位勾配により駆動され,外洋における典型的なエクマン螺旋構造とは異なる流れ場が形成される.また,湾内水位と高潮継続時間は低気圧経路に対する感度が高く,今後 2014年と同程度の規模の低気圧であっても経路によっては湾奥水位が非常に高くなる危険性があることを示す.
  • 猿渡 亜由未, 二宮 順一, 渡部 靖憲, 山田 朋人, 大塚 淳一, 馬場 康之, 水谷 英朗, 久保 輝広, 内山 雄介, 森 信人
    土木学会論文集A2(応用力学) 72 2 I_537 - I_547 公益社団法人 土木学会 2016年 [査読有り][通常論文]
     
    海から発生する波飛沫は大気-海洋間の熱,湿度,運動量の輸送量を決定すると共に,海塩粒子となって大気エアロゾルを構成することから,海上気象場に影響を与える重要なファクターの一つとなっている一方,その発生量は様々な要因に影響を受けることから精度良い見積もりが困難である.本研究では波飛沫発生量と気象,海象条件との関係を明らかにすることを最終的な目的とし,和歌山県田辺湾上において大気エアロゾルの粒子数密度の海上現地観測を行った.測定対象の三粒径(0.3, 1.0, 5.0 μm)のうち最も小さい粒子の数密度は観測期間を通して100 km以上のスケールの大気環境に支配され,平常時は波飛沫由来の海塩粒子の影響を多く含まないことが分かった.しかし太平洋側からの強風が卓越する気象イベント時においては何れの粒径の観測結果でも風速に対する単調増加傾向を示すことが確認された.この傾向は白波砕波が発生し始めると言われる海上風速6 ms-1以上の条件で表れ始めていることから,波飛沫由来の海洋性エアロゾル濃度の増加を観測した結果であると考える.
  • 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) 72 2 I_67 - I_72 公益社団法人 土木学会 2016年 [査読有り][通常論文]
     
    本研究では,遡上波先端の水面境界条件となるムービングコンタクトライン接触角経験モデルをLevel-set法ベースの自由水面流れ計算に導入する数値モデルを提案し,遡上波流れの接触依存性をダムブレークテストで検証する.また,2011年東北津波の釜石市街への浸水過程を模擬する都市浸水モデル地形における津波の防潮堤からの越流,街路への貯留に起因する段波の生成と伝播,不透過街区への衝突,さらに交差点での遡上波の合流,衝突過程の特徴を抽出し,典型的な津波の都市型浸水シナリオを提示する.
  • 猿渡 亜由未, 渡部 靖憲
    土木学会論文集B2(海岸工学) 71 2 1537 - 1542 2015年11月 [査読有り][通常論文]
  • Y. Watanabe, D. M. Ingram
    Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 471 2182 2015年10月08日 [査読有り][通常論文]
     
    © 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 2015年09月19日 [査読有り][通常論文]
     
    © 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  2015年09月 [査読有り][通常論文]
     
    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 2015年06月20日 [査読有り][通常論文]
     
    © 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  2015年06月 [査読有り][通常論文]
     
    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.
  • Shinji Kioka, Takahiro Takeuchi, Yasunori Watanabe
    Proceedings of the International Offshore and Polar Engineering Conference 2015-January 778 - 782 2015年 [査読有り][通常論文]
     
    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) 70 2 I_446 - I_450 2014年11月 [査読無し][通常論文]
     
    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 58 70 1177 - 1182 土木学会 2014年02月 [査読無し][通常論文]
  • 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 2014年01月01日 [査読有り][通常論文]
     
    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.
  • 渡部靖憲, 田代晃基, 大塚淳一, 大山高弘, 山田朋人
    土木学会論文集 B2(海岸工学)(Web) 70 2 I.56-I.60 (J-STAGE) - I_60 Japan Society of Civil Engineers 2014年 [査読無し][通常論文]
     
    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年 [査読無し][通常論文]
  • Measurement of Dissolved Carbon Dioxide Concentration in a Surf Zone
    J. Otsuka, Y. Watanabe, A. Saruwatari
    Proc. Int. Conf. Coastal Eng. 34 2014年 [査読無し][通常論文]
  • 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) 70 2 41 - 45 2014年 [査読有り][通常論文]
  • 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) 70 2 I_476 - I_480 公益社団法人 土木学会 2014年 [査読有り][通常論文]
  • Yasunori Watanabe, Shunichi Sato, Yasuo Niida, Ichiro Kimura, Hiroshi Yokota, Haruhi Oyaizu, Yuki Oshima, Ayumi Saruwatari
    Proceedings of the Coastal Engineering Conference 2014-January 2014年 [査読有り][通常論文]
     
    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 2014年 [査読有り][通常論文]
     
    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年02月 [査読無し][通常論文]
  • 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) 69 2 I_451 - I_455 公益社団法人 土木学会 2013年 [査読有り][通常論文]
     
    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)  2013年 [査読有り][通常論文]
  • 新井田 靖郎, 渡部 靖憲
    土木学会論文集. B2, 海岸工学 69 2 46 - 50 土木学会 2013年 [査読無し][通常論文]
  • 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 69 2 176 - 180 土木学会 2013年 [査読有り][通常論文]
  • 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 69 2 66 - 70 土木学会 2013年 [査読有り][通常論文]
  • 渡部 靖憲, 泉 典洋, 猿渡 亜由未
    土木学会論文集. B2, 海岸工学 69 2 51 - 55 土木学会 2013年 [査読有り][通常論文]
  • Yuta Mitobe, Yasunori Watanabe
    COASTAL STRUCTURES 2011, VOL 1 & 2 767 - 774 2013年 [査読有り][通常論文]
     
    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.
  • Yasunori Watanabe, Yuta Mitobe, Ayumi Saruwatari, Tomohito Yamada, Yasuo Niida
    Coastal Engineering Journal 54 1 2012年03月 [査読有り][通常論文]
     
    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 54 1 1250002 - 1250002 World Scientific Publishing 2012年03月 [査読有り][通常論文]
     
    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.
  • 渡部 靖憲, 堀井 正輝
    土木学会論文集. B2, 海岸工学 68 2 56 - 60 土木学会 2012年 [査読無し][通常論文]
  • 大塚 淳一, 渡部 靖憲, 林 倫史
    土木学会論文集. B2, 海岸工学 68 2 481 - 485 土木学会 2012年 [査読有り][通常論文]
  • 三戸部 佑太, 渡部 靖憲
    土木学会論文集. B2, 海岸工学 68 2 31 - 35 土木学会 2012年 [査読有り][通常論文]
  • 渡部 靖憲, 佐藤 駿一
    土木学会論文集. B2, 海岸工学 68 2 41 - 45 土木学会 2012年 [査読有り][通常論文]
  • Junichi Otsuka, Yasunori Watanabe
    Proceedings of the Coastal Engineering Conference 2012年 [査読有り][通常論文]
     
    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 2012年 [査読有り][通常論文]
     
    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 2011年12月 [査読有り][通常論文]
     
    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 2011年09月19日 [査読無し][通常論文]
     
    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 2011年07月 [査読有り][通常論文]
     
    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 67 2 66 - 70 土木学会 2011年 [査読有り][通常論文]
  • 森 信人, 加島 寛章, 渡部 靖憲
    可視化情報学会誌 31 1 63 - 68 可視化情報学会 2011年 [査読有り][通常論文]
  • 三戸部 佑太, 渡部 靖憲
    土木学会論文集. B2, 海岸工学 67 2 86 - 90 土木学会 2011年 [査読有り][通常論文]
  • 大塚 淳一, 渡部 靖憲
    土木学会論文集. B2, 海岸工学 67 2 91 - 95 土木学会 2011年 [査読有り][通常論文]
  • 渡部 靖憲, 岩下 厚志
    土木学会論文集. B2, 海岸工学 67 2 16 - 20 土木学会 2011年 [査読有り][通常論文]
  • 渡部 靖憲, 但木 慎治, 山田 朋人
    土木学会論文集. B2, 海岸工学 67 2 61 - 65 土木学会 2011年 [査読有り][通常論文]
  • 岩崎 理樹, 渡部 靖憲, 奥寺 亮太
    土木学会論文集. B2, 海岸工学 67 2 951 - 955 土木学会 2011年 [査読有り][通常論文]
  • Ayumi Saruwatari, Wataru Matsuzaki, Yasunori Watanabe
    Proceedings of the Coastal Engineering Conference 2010年12月01日 [査読無し][通常論文]
     
    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 2010年12月01日 [査読無し][通常論文]
     
    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 2010年12月01日 [査読無し][通常論文]
     
    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 2010年09月10日 [査読無し][通常論文]
     
    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 2010年09月10日 [査読無し][通常論文]
     
    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).
  • 渡部 靖憲
    日本流体力学会年会講演論文集 2010 0 293 - 293 日本流体力学会 2010年 [査読有り][通常論文]
     
    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
    土木学会論文集. B2, 海岸工学 66 1 86 - 90 土木学会 2010年 [査読無し][通常論文]
  • 渡部 靖憲, 石崎 真一郎, 新井田 靖郎
    土木学会論文集. B2, 海岸工学 66 1 76 - 80 土木学会 2010年 [査読無し][通常論文]
  • 渡部 靖憲, 坂井 純
    土木学会論文集. B2, 海岸工学 66 1 71 - 75 土木学会 2010年 [査読無し][通常論文]
  • Ayumi Saruwatari, Yasunori Watanabe, David M. Ingram
    COASTAL ENGINEERING 56 11-12 1109 - 1122 2009年11月 [査読有り][通常論文]
     
    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
    海岸工学論文集 56 0 831 - 835 土木学会 2009年10月 [査読無し][通常論文]
  • 渡部 靖憲, 三戸部 佑太
    海岸工学論文集 56 0 1466 - 1470 土木学会 2009年10月 [査読有り][通常論文]
  • 猿渡 亜由未, 渡部 靖憲
    海岸工学論文集 56 0 16 - 20 土木学会 2009年10月 [査読有り][通常論文]
  • 大塚 淳一, 渡部 靖憲
    海岸工学論文集 56 0 91 - 95 土木学会 2009年10月 [査読有り][通常論文]
  • 渡部 靖憲, 石崎 真一郎
    海岸工学論文集 56 0 11 - 15 土木学会 2009年10月 [査読有り][通常論文]
  • 渡部 靖憲, 新井田 靖郎, 猿渡 亜由未
    海岸工学論文集 56 0 6 - 10 土木学会 2009年10月 [査読有り][通常論文]
  • CHICHIBU Kohtaro, WATANABE Yasunori, SHIMIZU Yasuyuki
    Journal of hydroscience and hydraulic engineering 27 1 1 - 10 2009年05月01日 [査読有り][通常論文]
  • 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年 [査読有り][通常論文]
  • 砕波に伴う水中への二酸化炭素輸送に関する研究
    猿渡亜由未, 渡辺康太, 渡部靖憲
    海洋開発論文集 25 837 - 841 2009年 [査読有り][通常論文]
  • Yasunori Watanabe, Junichi Otsuka, Ayumi Saruwatari
    COASTAL ENGINEERING 2008, VOLS 1-5 51 - + 2009年 [査読有り][通常論文]
     
    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年 [査読有り][通常論文]
  • Ayumi Saruwatari, Yasunori Watanabe
    COASTAL ENGINEERING 2008, VOLS 1-5 73 - + 2009年 [査読有り][通常論文]
     
    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年 [査読有り][通常論文]
  • 渡部 靖憲, 田中 康文
    海岸工学論文集 55 0 846 - 850 土木学会 2008年10月 [査読有り][通常論文]
  • 猿渡 亜由未, 渡部 靖憲
    海岸工学論文集 55 0 61 - 65 土木学会 2008年10月 [査読有り][通常論文]
  • 渡部 靖憲, 石崎 真一郎
    海岸工学論文集 55 0 76 - 80 土木学会 2008年10月 [査読有り][通常論文]
  • 森 信人, 渡部 靖憲
    ながれ : 日本流体力学会誌 27 4 311 - 320 日本流体力学会 2008年08月25日 [査読有り][通常論文]
     
    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の可視化計測法について解説を行う.砕波現象における計測では,非定常性が強いため,点計測で現象を捉えることは困難であり,管路や開水路の流れと比較して,画像処理による計測法が有効となる.ここではバックライト法とPTVを組み合わせ,断面2次元空間に投影した気泡や飛沫形状と速度を同時に計測する手法についての概要と精度について事例を挙げつつ解説を行い,砕波帯における気泡や飛沫など混相特性について解説を行う.
  • WATANABE Yasunori, MORI Nobuhito
    J Geophys Res 113 C7 C07015-C07015-21  2008年07月22日 [査読有り][通常論文]
     
    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 2008年07月08日 [査読有り][通常論文]
     
    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 2008年07月 [査読有り][通常論文]
     
    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 227 4 2344 - 2365 Academic Press 2008年02月01日 [査読有り][通常論文]
     
    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.
  • K. Chichibu, Y. Watanabe, Y. Shimizu
    RIVER, COASTAL AND ESTUARINE MORPHODYNAMICS: RCEM 2007, VOLS 1 AND 2 1 627 - 632 2008年 [査読無し][通常論文]
     
    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 2007年12月01日 [査読無し][通常論文]
     
    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.
  • 加島 寛章, 森 信人, 渡部 靖憲, 大塚 淳一
    海岸工学論文集 54 1466 - 1470 公益社団法人 土木学会 2007年 [査読有り][通常論文]
     
    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.
  • 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 54 36 - 40 公益社団法人 土木学会 2007年 [査読有り][通常論文]
     
    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年 [査読有り][通常論文]
  • 大塚 淳一, 渡部 靖憲
    日本流体力学会年会講演論文集 2007 0 47 - 47 日本流体力学会 2007年 [査読有り][通常論文]
     
    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 2006年06月 [査読有り][通常論文]
     
    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.
  • 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年 [査読有り][通常論文]
  • 渡部靖憲, 猿渡亜由未
    海岸工学論文集 53 71 - 75 2006年 [査読有り][通常論文]
  • 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年 [査読有り][通常論文]
  • 秩父 宏太郎, 山下 智子, 渡部 靖憲
    応用力学論文集 9 659 - 666 土木学会 2006年 [査読有り][通常論文]
  • 渡部靖憲, 大友崇行, 猿渡亜由未
    海岸工学論文集 52 736 - 740 2005年 [査読有り][通常論文]
  • 長谷川 和義, 鈴木 洋之, 鈴木 優一, 田中 岳, 田中 仁, 藤間 聡, 中津川 誠, 八田 茂実, 村上 泰啓, 山下 俊彦, 山田 孝, 新谷 融, 渡邊 康玄, 渡部 靖憲, 藤田 睦博, 小川 長宏, 菊池 俊一, 黒木 幹男, 小松 利光, 嵯峨 浩, 清水 康行, 清水 収
    水工学論文集 49 49 427 - 432 公益社団法人 土木学会 2005年 [査読有り][通常論文]
     
    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.
  • 渡部 靖憲, Saeki Hiroshi, Hosking Roger J.
    Journal of Fluid Mechanics 545 545 291 - 328 Cambridge University Press 2005年 [査読有り][通常論文]
     
    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.
  • 渡部 靖憲
    混相流 18 3 巻頭  2004年09月15日 [査読有り][通常論文]
  • 森 信人, 渡部 靖憲
    土木学会論文集 = Proceedings of JSCE 768 101 - 111 土木学会 2004年08月21日 [査読有り][通常論文]
  • 渡部 靖憲, 森 信人
    土木学会論文集 = Proceedings of JSCE 768 89 - 100 土木学会 2004年08月21日 [査読有り][通常論文]
  • 竹内 貴弘, 中澤 直樹, 三上 隆, 渡部 靖憲, 佐伯 浩
    海洋開発論文集 20 20 1223 - 1227 公益社団法人 土木学会 2004年 [査読有り][通常論文]
     
    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.
  • 佐藤 典之, 渡部 靖憲, 秀島 賢保, 近藤 浩文, 佐伯 浩
    海洋開発論文集 20 20 1305 - 1310 公益社団法人 土木学会 2004年 [査読有り][通常論文]
     
    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.
  • Masaya Kato, Yasunori Watanabe, Hiroshi Saeki
    Proceedings of the Coastal Engineering Conference 2003- 1661 - 1670 2003年 [査読無し][通常論文]
     
    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.
  • 渡部 靖憲
    可視化情報学会誌 = Journal of the Visualization Society of Japan 22 0 383 - 384 2002年07月01日 [査読有り][通常論文]
  • Y Watanabe, H Saeki
    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS 39 7 607 - 637 2002年07月 [査読無し][通常論文]
     
    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.
  • 波動場におけるブロック潜堤間隙内の三次元流体運動に関する実験的研究
    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 49 791 - 795 2002年 [査読無し][通常論文]
  • 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年 [査読有り][通常論文]
  • Masaya Kato, Yuhki Okumura, Yasunori Watanabe, Hiroshi Saeki
    Proceedings of the International Symposium on Ocean Wave Measurement and Analysis 2 1126 - 1135 2001年12月01日 [査読無し][通常論文]
     
    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年12月01日 [査読無し][通常論文]
     
    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.
  • 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年 [査読有り][通常論文]
     
    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年 [査読有り][通常論文]
     
    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年12月01日 [査読無し][通常論文]
     
    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.
  • 加藤 雅也, 渡部 靖憲, 佐伯 浩
    海洋開発論文集 16 16 75 - 80 公益社団法人 土木学会 2000年 [査読有り][通常論文]
     
    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 2000年 [査読無し][通常論文]
     
    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
    Coastal engineering journal 41 3 281 - 301 1999年12月01日 [査読有り][通常論文]
     
    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.
  • 早川 哲也, 木村 克俊, 林 忠志, 土井 善和, 渡部 靖憲
    海洋開発論文集 15 15 713 - 717 土木学会 1999年 [査読有り][通常論文]
     
    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.
  • 早川 哲也, 木村 克俊, 林 忠志, 土井 善和, 渡部 靖憲
    海洋開発論文集 15 713 - 717 土木学会 1999年 [査読無し][通常論文]
     
    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.
  • 大島 香織, 大塚 夏彦, 石川 博基, 高橋 伸次郎, 渡部 靖憲, 橘 治国, 佐伯 浩
    海洋開発論文集 15 15 559 - 564 公益社団法人 土木学会 1999年 [査読有り][通常論文]
     
    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.
  • 渡部 靖憲, 松本 靖治, 早川 哲也, 王 毅, 大塚 淳一, 安原 幹雄, 佐伯 浩
    海洋開発論文集 15 15 375 - 380 公益社団法人 土木学会 1999年 [査読有り][通常論文]
     
    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, 松本 靖治, 佐伯 浩
    海岸工学論文集 45 45 136 - 140 公益社団法人 土木学会 1998年 [査読有り][通常論文]
  • 渡部 靖憲, 森 憲広, 佐伯 浩
    海岸工学論文集 45 45 146 - 150 公益社団法人 土木学会 1998年 [査読有り][通常論文]
  • 渡部 靖憲, 梅田 克史, 佐伯 浩
    海岸工学論文集 45 45 121 - 125 公益社団法人 土木学会 1998年 [査読有り][通常論文]
  • 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 45 691 - 695 土木学会 1998年 [査読無し][通常論文]
     
    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年01月01日 [査読無し][通常論文]
     
    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年 [査読無し][通常論文]
     
    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 45 45 691 - 695 土木学会 1998年 [査読有り][通常論文]
     
    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, 佐伯 浩, 森 憲広, 稲垣 啓
    海洋開発論文集 13 13 865 - 870 公益社団法人 土木学会 1997年 [査読有り][通常論文]
     
    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.
  • 早川 知子, 北村 泰介, 佐藤 正樹, 木下 千里, 渡部 靖憲, 佐伯 浩
    海洋開発論文集 13 13 837 - 842 公益社団法人 土木学会 1997年 [査読有り][通常論文]
     
    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 1997年 [査読無し][通常論文]
     
    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.
  • Y Watanabe, H Saeki
    HYDRAULIC ENGINEERING SOFTWARE VI 385 - 394 1996年 [査読有り][通常論文]
     
    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.
  • 渡部 靖憲, 森 憲広, 黒木 幹男, 佐伯 浩
    海洋開発論文集 12 12 37 - 42 公益社団法人 土木学会 1996年 [査読有り][通常論文]
     
    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.
  • Y WATANABE, H SAEKI, K HAMANAKA
    PROCEEDINGS OF THE FIFTH (1995) INTERNATIONAL OFFSHORE AND POLAR ENGINEERING CONFERENCE, VOL III 64 - 69 1995年 [査読有り][通常論文]
  • 奥村 慎也, 佐藤 幸雄, 渡部 靖憲
    海岸工学論文集 42 42 831 - 835 公益社団法人 土木学会 1995年 [査読有り][通常論文]
  • 渡部 靖憲, 佐伯 浩
    海岸工学論文集 42 42 116 - 120 公益社団法人 土木学会 1995年 [査読有り][通常論文]
  • 渡部 靖憲, 細川 裕希, 佐伯 浩
    海岸工学論文集 42 42 106 - 109 公益社団法人 土木学会 1995年 [査読有り][通常論文]
  • 折橋 恒春, 渡部 靖憲, 浜中 建一郎
    海岸工学論文集 41 41 26 - 30 公益社団法人 土木学会 1994年 [査読有り][通常論文]
  • Y. Watanabe, T. Orihashi, K. Hamanaka, Y. Sato
    National Conference Publication - Institution of Engineers, Australia 1 229 - 234 1993年01月01日 [査読無し][通常論文]
     
    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 39 2 1061 - 1065 1992年11月 [査読無し][通常論文]
  • 石井千万太郎, 佐藤英泰, 折谷徳弘, 渡部靖憲, 佐伯浩, 山下俊彦
    海洋開発論文集 8 195 - 199 1992年 [査読無し][通常論文]

書籍

講演・口頭発表等

その他活動・業績

  • 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年 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
  • 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年01月 [査読無し][通常論文]
  • 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年01月 [査読無し][通常論文]
  • 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年01月 [査読無し][通常論文]
  • 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年01月 [査読無し][通常論文]
  • 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年01月 [査読無し][通常論文]
  • 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年01月 [査読無し][通常論文]
  • 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年01月 [査読無し][通常論文]
  • 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年01月 [査読無し][通常論文]
  • 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年01月 [査読無し][通常論文]
  • 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年01月 [査読無し][通常論文]
  • 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年01月 [査読無し][通常論文]
  • Sediment suspension in violent breaking waves
    Yasunori Watanabe, Ayumi Saruwatari 12th European Fluid Mechanics Conference 2018年09月 [査読無し][通常論文]
  • 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年03月31日 [査読無し][通常論文]
  • 渡部靖憲, 杉村一直, 猿渡亜由未 日本混相流学会混相流シンポジウム 2018 WEB ONLY 2018年 [査読無し][通常論文]
  • 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年09月 [査読有り][通常論文]
  • 渡部靖憲 土木学会誌 102 (8) 44‐45 2017年08月15日 [査読無し][通常論文]
  • 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年02月 [査読無し][通常論文]
  • 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年02月 [査読無し][通常論文]
  • 岡地 寛季, 山田 朋人, 渡部 靖憲, 大塚 淳一 水文・水資源学会研究発表会要旨集 30 (0) 95 -95 2017年 [査読有り][通常論文]
     
    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.
    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年03月 [査読有り][通常論文]
  • 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 水文・水資源学会研究発表会要旨集 29 (0) 2016年 [査読無し][通常論文]
     
    地球温暖化に伴う海面の上昇は,台風の頻度と強度,及び他の極端現象と関係を有する.既往研究は,海上に生じる飛沫が台風の発達に寄与することを示した.しかし飛沫の影響及び発生メカニズムは不明点があり,現在広く使用されている気象モデル及び天気予報には飛沫の影響は考慮されていない.そこで発表者らは飛沫の正確な観測データから解析を行い不明点を解明するべく,ピストン式造波装置付き水路を用いた風洞実験を行っている.しかし実験室スケールの実験は台風のスケールと異なるので,台風を直接観測したデータを利用して比較解析する必要がある.本研究は発表者らによる和歌山県近郊の田辺湾に設置した飛沫の粒径観測の結果をレポートするものである.今回の使用した観測機器パーシベルは本来雨滴観測用に用いられる観測機器であるが,観測粒径範囲が他の観測機器より比較的大きいため今回の観測に利用した.上記の発表者らの観測地では,2015年の台風イベント発生時において,1.5~5.510mm粒径の飛沫が観測された.発表時には,観測地に基づく強風下における飛沫と風速の関係を議論する.
  • 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年 [査読有り][通常論文]
  • 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年09月02日 [査読無し][通常論文]
  • 木岡信治, 竹内貴弘, 渡部靖憲 混相流 29 (2) 124 -131 2015年06月15日 [査読無し][通常論文]
  • 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年 [査読有り][通常論文]
  • 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年 [査読有り][通常論文]
     
    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.
  • 田代晃基, 渡部靖憲, 山田朋人, 大塚淳一, 大山高弘 土木学会北海道支部論文報告集(CD-ROM) (70) ROMBUNNO.B-65 2014年02月 [査読無し][通常論文]
  • 大山高弘, 山田朋人, 渡部靖憲, 大塚淳一 土木学会北海道支部論文報告集(CD-ROM) (70) ROMBUNNO.B-64 2014年02月 [査読無し][通常論文]
  • 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年 [査読有り][通常論文]
     
    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.
  • 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年 [査読有り][通常論文]
     
    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年03月 [査読有り][通常論文]
  • 渡部靖憲 海と港 (29) 59 -67 2011年08月10日 [査読無し][通常論文]
  • 渡部 靖憲 可視化情報学会誌 31 (1) 19 -22 2011年 [査読有り][通常論文]
  • 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年 [査読無し][通常論文]
  • 大塚 淳一, 日端 弾, 渡部 靖憲 海岸工学論文集 54 (54) 51 -55 2007年 [査読有り][通常論文]
     
    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.
  • 猿渡 亜由未, 渡部 靖憲 海岸工学論文集 54 (54) 66 -70 2007年 [査読有り][通常論文]
     
    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.
  • 大島 香織, 森屋 陽一, 大塚 淳一, 渡部 靖憲 海岸工学論文集 54 (54) 796 -800 2007年 [査読有り][通常論文]
     
    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年 [査読有り][通常論文]
     
    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年 [査読有り][通常論文]
     
    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.
  • 渡部 靖憲 可視化情報学会誌 22 (1) 383 -384 2002年 [査読有り][通常論文]
     
    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年 [査読有り][通常論文]
     
    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年 [査読有り][通常論文]
     
    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年 [査読有り][通常論文]
     
    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年 [査読有り][通常論文]
     
    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年 [査読有り][通常論文]
  • 渡部 靖憲, 安原 幹雄, 佐伯 浩 海岸工学論文集 46 (46) 141 -145 1999年 [査読有り][通常論文]
  • 渡部 靖憲, 王 毅, 早川 哲也, 佐伯 浩 海岸工学論文集 46 (46) 741 -745 1999年 [査読有り][通常論文]

共同研究・競争的資金等の研究課題

  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2015年 -2018年 
    代表者 : 渡部 靖憲
  • 文部科学省:科学研究費補助金(挑戦的萌芽研究)
    研究期間 : 2015年 -2017年 
    代表者 : 渡部 靖憲
  • 文部科学省:科学研究費補助金(挑戦的萌芽研究)
    研究期間 : 2012年 -2014年 
    代表者 : 渡部 靖憲
     
    計測タイミング制御アルゴリズム開発本計測システムで使用する市販のPCプロジェクタを使ってプロジェクタ投影固有周期以上で高速撮影を行う場合には,対象物上に単色のみ投影された画像となるためカラー抽出処理が不能となる.この投影照明に起因する障害を解決するため,昨年度購入した各色の投影時間間隔,強度,パターンを制御可能なプログラマブル・プロジェクタを導入し,タイミングコントローラを介して高速カメラと完全に同期する本形状計測に特化したシステムを構成した.マルチレベル空間最適化法によるカラーパターン追跡アルゴリズムの開発オプティカルフローの解析法の一つである空間最適化法を適用し,連続した画像上において対象表面に投影された同一カラーブロックを追跡し,動的なブロック位置の特定を行うことにより対応ブロック検出の自動化を行った.これは,画像上のカラーブロックの色をRGB分解したうえで,連続する画像上のそれぞれの色要素の輝度が保存されるよう移動速度の最適解を変分原理を基に決定するものである.さらに,高解像計測画像において高速でカラーブロック追跡処理を行うため,画像を複数の解像度レベルに分解し,低レベルの最適解から効率的に高レベル解を連動して求めるマルチレベル法を適用するための基本アルゴリズムを開発した.水中からの散乱光補正自由水面を計測する場合,水中のランベルト多重散乱系がつくる光が水面特定の精度を著しく低下させることが新たに判明した.この散乱光による誤差を補正するための基礎アルゴリズムを考案し,システムへの導入を進めた.今年度行う精度検証において,この計測誤差の特徴を明らかにする予定である.
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2012年 -2014年 
    代表者 : 渡部 靖憲, 森 信人, 山田 朋人
     
    タスク1暴風下の大気海洋界面の気液乱流シミュレータの開発研究代表者渡部,研究協力者Ingramと共同で気液乱流ソルバーの最適化,並列化,そして熱流体モデルとサブグリッド粒子確率モデルを統合し,飛沫気泡を含む気液せん断乱流境界層内の熱輸送を再現するため大気海洋気液乱流シミュレータの開発を進めた.また,砕波の乱流量を支配する基本パラメータである流体の伸張と渦度によって局所水面形及び飛沫サイズ並びに個数を決定するメカニズムを明らかにするため,線型安定性解析を新たに進め,パラメータスタディに対する理論的サポートを構築した.タスク2ストームイベントにおける海面過程による熱,気体輸送フラックスの可視化計測砕波過程に対するバックライト気泡飛沫画像計測,海面飛沫の高速熱赤外線計測及びLIFによる酸素並びに二酸化炭素濃度計測を行い,乱流強度,混入気泡サイズ及び飛沫サイズ分布をパラメータとした気体及び海中への輸送フラックスを定量化するめの統計量を取得した.高速赤外線カメラの特性を把握し,液滴の着水に伴う熱遷移評価に対するテストケースを実施し,可視画像情報から水温情報のみを取得するための効率的な解析法を確立した.タスク3海面上マイクロメカニクスによる熱気体輸送パラメタリゼーション本年度実施する現地観測ため,降雨,エアロゾル,そして飛沫水を分離しサンプリングすることで,相互に指標化を行うための新たな方法を考案した.砕波,降雨イベントにおけるマイクロメカニクスとタスク2で得られた同パラメータに対する輸送フラックスを結合しモデル化を行うための準備を進めた.
  • 文部科学省:科学研究費補助金(挑戦的萌芽研究)
    研究期間 : 2009年 -2011年 
    代表者 : 渡部 靖憲
     
    この研究は,力学的刺激に対して発光する体長約数十μm程度の微生物を計測メディアとして流体中に混入し,微生物の発光分布から流体にはたら流体力分布を算定する計測法を開発するものである.短時間に主応力が変化する衝撃動圧力下において,最大圧力,力積は平均最大発光強度と高く相関し,また剥離を伴う振動流境界層内のせん断力分布と発光強度の統計量ものまた相関する.決定した線形較正式からこれら流体力を決定できる.
  • 文部科学省:科学研究費補助金(基盤研究(A))
    研究期間 : 2007年 -2010年 
    代表者 : 清水 康行, 泉 典洋, 渡部 靖憲, 竹林 洋史, 渡邊 康玄, 安田 浩保
     
    本研究の目的は,集中豪雨に伴う洪水氾濫流及び河川流域内の表面及び浸透流とそれらに駆動される土砂流及び流動地盤を連成して評価し得る数値モデルを構築し,近年中小河川流域で頻発している異常流出が原因となる河道や河床だけでなく流域の地形をも大きく変化させる大規模な土砂流動の予測法を確立することである.
  • 文部科学省:科学研究費補助金(基盤研究(C))
    研究期間 : 2007年 -2008年 
    代表者 : 森 信人, 渡部 靖憲, 渡部 靖憲, 竹原 幸生
     
    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.
  • 文部科学省:科学研究費補助金(若手研究(B))
    研究期間 : 2006年 -2008年 
    代表者 : 渡部 靖憲
     
    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。
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2004年 -2006年 
    代表者 : 清水 康行, 渡邊 康玄, 泉 典洋, 竹林 洋史, 渡部 靖憲
     
    近年、弱非線形安定解析や数値計算を用いた研究によって移動床現象の解明が飛躍的に進んでいる.しかし一方で強非線形性に由来する多くの現象が依然として未解明のまま残されており、本研究ではこのうちの代表的な現象を明らかにした.清水は2次元非静水圧の流れの運動方程式、連続式と乱流モデルおよび非平衡の流砂量式を組み合わせ、河床波の発生、発達、移動、減衰を再現することに成功した。特に、河床波の発達に伴い河床抵抗が変化し、いわゆる粗度が変化することを物理モデルで予測することに成功したのは世界的にも初めてであり、工学的に極めて重要な成果である.泉は,平均河床勾配が小さく流速係数が大きい領域においてデューン-平坦床遷移は亜臨界分岐となることが明らかにした,また,線形安定解析を用いた水路群の形成モデルを改良し,任意形状の斜面に適用できるよう理論を拡張し、斜面の曲率が適当な範囲にあるとき,水深の1000倍程度の水路群が生じることを明らかにした.渡邊は非定常流量条件下での複列砂州の挙動を明らかにするため,水理実験および弱非線形安定解析を実施した.その結果,平常時の流路形状が洪水時に形成される中規模河床波の形状に強く支配されていることを明らかにした.竹林は数値解析と理論解析により,混合砂河床においては,複数の特性量が異なる伝播速度で伝播し,砂州は発生と消滅を繰り返すことを明らかにした.渡部は固液同時速度...
  • 文部科学省:科学研究費補助金(若手研究(B))
    研究期間 : 2003年 -2005年 
    代表者 : 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.
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2003年 -2005年 
    代表者 : 重松 孝昌, 渡部 靖憲, 竹原 幸生
     
    本研究は,固液混相流の三次元乱流構造を解明するための計測手法を開発することを目的とした研究で,竹原の開発したSuper-Resolution PIV法の時間解像度の向上を,また,同時に,渡部の開発した三次元ステレオPIVの時間・空間解像度の向上に取り組んだものである.Super-Resolution PIVは多数のトレーサー粒子の解析も可能で高空間解像度を有する計測が可能であるが,計測システム上,時間解像度が十分ではないという課題を有していた.この点については,高時間・高空間解像度ビデオ計測システムの購入により改善された.本計測システムによって得られた画像に基づいて多孔質体間隙部およびその近傍の流速計測を行い,Super-Resolution PIVを用いて解析を行うことによって,多孔質体を通過する際の乱れの生成・減衰機構について詳細な検討を行うに至った.三次元ステレオPIVは,三次元計測が可能であるが,トレーサー粒子数が多くなると解析に膨大な時間を要するという課題があった。この点については,アルゴリズムを改善することによって改善を図り,低コストかつ高解像度の計測システムへと再構築した.改善された三次元ステレオPIV法を砕波帯下の混相流場へ適用し,複雑な運動を呈する流体および底質の挙動解析が行えるに至った,さらに,高濃度粒子群に誘起される極めて流速の早い流体運動を伴う固液混相...
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2003年 -2004年 
    代表者 : 佐伯 浩, 渡部 靖憲
     
    昨年度までの研究成果を踏まえ、環境パラメータの確率分布を考慮したIce Scour Eventのシミュレーション手法を構築した。そのシミュレーション結果と実海域での観測データと比較した結果、実海域での掘削深(Scour depth)、Scour lengthのオーダーとその確率分布は概ね一致したほか、Eventの発生率など、物理環境条件にともなう大局的な傾向特性は概ね一致し、その妥当性が示された。さらにそのシミュレーションデータを用い、パイプライン等埋設構造物のライフタイム、Keelの発生過程・発生数を考慮すれば、破壊確率(パイプラインと氷との干渉・接触確率)が計算でき、氷(keel)の地盤への掘削深推定手法をサブプログラムとした合理的な埋設深度推定手法・方法論を開発した。その概念は環境の不確定要素が卓越した場合の安全性評価が可能となる信頼性理論に立脚したものと考えることができる。また、Sub-scour deformationによる付加的な応力を考慮し、安全なパイプラインの埋設深度を推定することを目的として、昨年度実施した小規模実験に続き、中規模模型実験を実施した。両実験結果より反力と地盤内応力分布の力学的相似を明らかにした。また、地盤内応力によるパイプラインの応答解析モデルを構築し、実測値と比較した結果、両者は概ね一致した。この手法により、スケール効果を考慮したパイプライ...
  • 文部科学省:科学研究費補助金(基盤研究(A))
    研究期間 : 1999年 -2002年 
    代表者 : 佐伯 浩, 橘 治国, 渡部 靖憲
     
    平成14年度は以下の課題を明らかにした。(1)結氷に至る前段階である、氷晶の移動制御について系統的な実験を行い、アイスブームにより移動制御が可能である事を示すとともに、その限界流速についても明らかにした。これにより閉鎖性水域の結氷防止対策の一つとして利用可能であることを示した。(2)流氷移動の制御にアイスブームを用いた場合の海水交換への影響をサロマ湖を例に数値計算を行い、開氷期、結氷期それに流氷制御時の海水交換量を明らかにするとともに、湖内の流動特性も明らかにした。(3)また、閉鎖水域の波浪を含めた流動計算の計算精度向上を目的に浅水域や構造物近傍の波動の三次元数値解析手法の高度化を計った。(4)オホーツク海沿岸地域は、酪農,畑作地帯であることから、それらからの地下水、河川への汚濁負荷と、その実態について詳細な現地調査を行った。(5)過去4年間の研究成果のまとめも行った。
  • 文部科学省:科学研究費補助金(奨励研究(A))
    研究期間 : 2000年 -2001年 
    代表者 : 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))
    研究期間 : 1998年 -1999年 
    代表者 : 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.

教育活動情報

主要な担当授業

  • Ocean Wave Mechanics(沿岸波動力学E)
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 工学院
    キーワード : Water wave theory Wave equation Wave spectrum Wave statistics Coastal disasters
  • 沿岸波動力学特論
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 工学院
    キーワード : Water wave theory Wave equation Wave spectrum Wave statistics Coastal disasters
  • Ocean Wave Mechanics(沿岸波動力学E)
    開講年度 : 2018年
    課程区分 : 博士後期課程
    開講学部 : 工学院
    キーワード : Water wave theory Wave equation Wave spectrum Wave statistics Coastal disasters
  • 沿岸波動力学特論
    開講年度 : 2018年
    課程区分 : 博士後期課程
    開講学部 : 工学院
    キーワード : Water wave theory Wave equation Wave spectrum Wave statistics Coastal disasters
  • 水理学Ⅱ
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 等流,急変流,漸変流,常流と射流,非定常流
  • 数値計算法演習
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 微分方程式・統計解析・Fortran・Matlab・可視化・プレゼンテーション
  • 流体力学
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 流体の運動 完全流体 粘性流体 流体力 水の波
  • 一般教育演習(フレッシュマンセミナー)
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : 流れ,渦,波,自然災害,気候変動


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