研究者データベース

泉 典洋(イズミ ノリヒロ)
工学研究院 土木工学部門 社会基盤マネジメント
教授

基本情報

所属

  • 工学研究院 土木工学部門 社会基盤マネジメント

職名

  • 教授

学位

  • 学術博士(Ph. D.)(ミネソタ大学(アメリカ合衆国))

ホームページURL

J-Global ID

研究キーワード

  • 河川水理学   安定性   土砂輸送   河川地形   River Hydraulics Fluid Mechanics Sediment Transport Fluvial Morphology   Stability   Sediment Transport   Fluvial Geomorphology   

研究分野

  • 社会基盤(土木・建築・防災) / 水工学

職歴

  • 2010年 - 北海道大学大学院工学研究院 教授
  • 2010年 - Professor,Hokkaido University, Faculty of Engineering
  • 2001年 - 2006年 東北大学大学院工学研究科 助教授
  • 2001年 - 2006年 Associate Professor,Tohoku University, Graduate School of Engineering
  • 1999年 - 2001年 アジア工科大学大学院土木工学部 助教授
  • 1999年 - 2001年 Associate Professor,Asian Institute of Technology, School of Civil Engineering
  • 1996年 - 1999年 東北大学工学部土木工学科 助教授
  • 1996年 - 1999年 Associate Professor,Tohoku University, Faculty of Engineering
  • 1993年 - 1996年 東京工業大学工学部土木工学科 助手
  • 1993年 - 1996年 Research Associate,Tokyo Institute of Technology, Faculty of Engineering

学歴

  •         - 1993年   ミネソタ大学大学院(University of Minnesota, Graduate School)   工学研究科   土木工学専攻(Civil Engineering)
  •         - 1993年   University of Minnesota, Graduate School
  •         - 1987年   東京大学   工学部   土木工学科(Civil Engineering)
  •         - 1987年   東京大学

所属学協会

  • 日本地形学連合   日本海洋学会   日本流体力学会   土木学会   土木学会応用力学委員会   Japanese Geomorphological Union   The Oceanographic Society of Japan   Japan Society of Civil EngineersJapan Society of Fluid Mechanics   

研究活動情報

論文

  • Furuichi Takahisa, Osanai Nobutomo, Hayashi Shin-ichiro, Izumi Norihiro, Kyuka Tomoko, Shiono Yasuhiro, Miyazaki Tomoyoshi, Hayakawa Tomoya, Nagano Norihiro, Matsuoka Naoki
    LANDSLIDES 15 8 1645 - 1655 2018年08月 [査読有り][通常論文]
  • 恒川 和久, リマ アドリアーノ, 泉 典洋
    水工学論文集 62 Ⅰ_571 - 576 土木学会 2018年 [査読有り][通常論文]
  • 久原 愛加, デ・リマ・アドリアーノ, 泉 典洋
    水工学論文集 62 Ⅰ_607 - 612 土木学会 2018年 [査読有り][通常論文]
  • 田口 真矢, 小林 素直, リマ アドリアーノ, 泉 典洋
    水工学論文集 62 Ⅰ_1039 - 1044 土木学会 2018年 [査読有り][通常論文]
  • ペン シサリス, 泉 典洋, 萩澤 さくら
    水工学論文集 62 Ⅰ_1105 - 1110 土木学会 2018年 [査読有り][通常論文]
  • 山口 里実, 久加 朋子, 清水 康行, 泉 典洋, 渡邊 康玄, 岩崎 理樹
    水工学論文集 62 Ⅰ_1153 - 1158 土木学会 2018年 [査読有り][通常論文]
  • 泉 典洋
    水工学論文集 63 I_811 - 816 土木学会 2018年 [査読有り][通常論文]
  • 住友 慶三, 渡邊 康玄, 泉 典洋, 山口 里実, 米元 光明
    水工学論文集 63 I_1003 - 1008 土木学会 2018年 [査読有り][通常論文]
  • 山口進, 井上卓也, 赤堀良介, 佐藤大介, 清水康行, 泉典洋
    水工学論文集 63 I_1153 - 1158 土木学会 2018年 [査読有り][通常論文]
  • Lima A. C, Izumi N
    JOURNAL OF HYDRAULIC RESEARCH 56 2 211 - 220 2018年 [査読有り][通常論文]
  • Pornprommin Adichai, Izumi Norihiro, Parker Gary
    JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE 122 12 2348 - 2369 Wiley-Blackwell 2017年12月 [査読有り][通常論文]
  • 田口 真矢, 小澤 春貴, リマ アドリアーノ, 泉 典洋
    水工学論文集 61 Ⅰ_847 - 852 土木学会 2017年 [査読有り][通常論文]
  • 田口 真矢, 小澤 春貴, LIMA Adriano C, 泉 典洋
    土木学会論文集B1(水工学) 73 4 I_847 - I_852 公益社団法人 土木学会 2017年 [査読有り][通常論文]
     
    近年,多くの河川において基盤岩の露出による岩盤河床の侵食が深刻な問題となっている.岩盤河床の侵食は流砂の摩耗現象により引き起こされるため,河床上の砂礫堆積箇所と基盤岩の露出箇所を知ることは岩盤河床の侵食を考える際に重要となる.二次流により内岸で砂礫の堆積,外岸で基盤岩の露出が見られる湾曲部においては,ある特徴を持った岩盤河床の侵食が発生すると予測できる.<br> 本研究では,湾曲部における岩盤河床の侵食に着目し,一様湾曲水路を用いた室内実験を行うことで岩盤河床の侵食を再現した.そして,湾曲部における岩盤河床の侵食発生箇所及び河床変化の動態についていくつかの特徴を観測することができた.本論文では,実験結果とその特徴について報告する.
  • 小田 圭祐, 前田 勇司, 西浦 泰介, 野村 瞬, 泉 典洋, 西畑 剛, 阪口 秀
    土木学会論文集B3(海洋開発) 73 2 I_660 - I_665 公益社団法人 土木学会 2017年 [査読有り][通常論文]
     
    津波が来襲したとき,その大きな掃流力や乱れによって大量の海底土砂が輸送される.これまでに津波による海底土砂輸送量に関する研究や地形変化に関する研究は数多くなされているが,河床変化や波による海底地形変化のような微視的な地形変化に関する研究や,津波フロントや後続波といったイベントごとの地形変化に着目した例は少ない.そこで,本研究では津波到達時から後続波による砂漣形成初期までの地形変化の形態を把握し,津波外力規模と砂漣の形成,消失との関係を明らかにすることを目的とし,移動床水理模型実験を行った.その結果,比較的流速の小さい後続波によって砂漣が形成されること,津波後続波による地形形態は河川の地形変化特性で用いられる指標と概ね一致すること,砂漣の峰には粗粒砂が多く堆積し,谷には細粒砂が堆積することなどがわかった.
  • Norihiro Izumi, Miwa Yokokawa, Gary Parker
    JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE 122 1 130 - 152 2017年01月 [査読有り][通常論文]
     
    Most bedrock river channels have a relatively thin, discontinuous cover of alluvium and are thus termed mixed bedrock-alluvial channels. Such channels often show a series of steps formed at relatively regular intervals. This bed form is the bedrock equivalent of cyclic steps formed on beds composed of cohesive soil in gullies. In this paper, we perform a full nonlinear analysis for the case of cyclic steps in mixed bedrock-alluvial channels to explain the formation of these steps. We employ the shallow water equations in conjunction with equations describing the process of bedrock incision. As a model of bedrock incision, we employ the recently introduced Macro-Roughness Saltation Abrasion Alluviation model, which allows direct interaction between alluvial and bedrock morphodynamics. The analysis is greatly simplified by making the quasi-steady assumption that alluvial processes occur much faster than bedrock erosional processes. From our analysis, we obtain the conditions for the formation of cyclic steps in bedrock, as well as the longitudinal profiles of bed elevation, water surface elevation, and areal fraction of alluvial cover. It is found from the analysis that when the sediment supply is small relative to the transport capacity, cyclic steps form only on slopes with very high gradients. The analysis indicates that the shape of a step formed on bedrock is characterized by a relatively short upstream portion with an adverse slope and a long, almost planar downstream portion with a constant slope.
  • Adriano C. de Lima, Norihiro Izumi
    JOURNAL OF HYDRAULIC ENGINEERING 142 12 2016年12月 [査読有り][通常論文]
     
    The comparison between spatial and temporal growth of perturbations in a shear layer is revisited for the case of a viscous open-channel flow with velocity inflection. Turbulence is characterized by two distinct scales: a subdepth turbulence associated with the bed shear stress and a large-scale turbulence associated with the large horizontal eddies that develop in the shear layer. Temporal and spatial linear stability analyses are performed. The base flow is assumed to be affected only by the subdepth scale turbulence. Therefore, the base flow represents not the average flow but the flow completely free of the effect of the instability of the shear layer. Temporal and spatial approaches present less discrepancy in the viscous than in the previously analyzed in-viscous case. In particular, the phase velocity was found to be strongly correlated to the frequency in both the temporal and spatial approaches. (C) 2016 American Society of Civil Engineers.
  • T. Inoue, T. Iwasaki, G. Parker, Y. Shimizu, N. Izumi, C. P. Stark, J. Funaki
    JOURNAL OF HYDRAULIC ENGINEERING 142 7 2016年07月 [査読有り][通常論文]
     
    Natural bedrock rivers exhibit diverse erosional morphologies. Although the formation of alternate bars on bedrock has been noted in previous studies, the influence of these alternate bars on bedrock erosion has not been clarified. In this study, the authors propose a model for bedrock-alluvial channels that reproduces both bar formation and erosional morphology. In addition, the authors report on numerical simulations to evaluate the influence of sediment supply on the state of the bed at and over the bedrock surface. The numerical results illustrate the formation of different morphologies for different supply rates. When the sediment supply rate is close to transport capacity, mixed alluvial-bedrock alternate bars form. These bars are analogous to purely alluvial alternate bars. A meandering thread of alluvial material migrates downstream over a uniformly eroding bedrock surface. When the sediment supply rate is well below capacity, however, multiple incisional troughs (grooves) form on the bedrock surface, and alluvial cover tends to concentrate in the troughs.
  • M. Yokokawa, N. Izumi, K. Naito, G. Parker, T. Yamada, R. Greve
    JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE 121 5 1023 - 1048 2016年05月 [査読有り][通常論文]
     
    Boundary waves often form at the interface between ice and fluid flowing adjacent to it, such as ripples under river ice covers, and steps on the bed of supraglacial meltwater channels. They may also be formed by wind, such as the megadunes on the Antarctic ice sheet. Spiral troughs on the polar ice caps of Mars have been interpreted to be cyclic steps formed by katabatic wind blowing over ice. Cyclic steps are relatives of upstream-migrating antidunes. Cyclic step formation on ice is not only a mechanical but also a thermodynamic process. There have been very few studies on the formation of either cyclic steps or upstream-migrating antidunes on ice. In this study, we performed flume experiments to reproduce cyclic steps on ice by flowing water, and found that trains of steps form when the Froude number is larger than unity. The features of those steps allow them to be identified as ice-bed analogs of cyclic steps in alluvial and bedrock rivers. We performed a linear stability analysis and obtained a physical explanation of the formation of upstream-migrating antidunes, i.e., precursors of cyclic steps. We compared the results of experiments with the predictions of the analysis and found the observed steps fall in the range where the analysis predicts interfacial instability. We also found that short antidune-like undulations formed as a precursor to the appearance of well-defined steps. This fact suggests that such antidune-like undulations correspond to the instability predicted by the analysis and are precursors of cyclic steps.
  • 松田 達也, 前田 健一, 泉 典洋, 伊藤 嘉, 山口 敦志, 鶴ヶ崎 和博, 宮本 順司
    土木学会論文集B2(海岸工学) 72 2 I_565 - I_570 公益社団法人 土木学会 2016年 [査読無し][通常論文]
     
    自由表面流れによる洗掘では,地盤表層に作用する掃流力に加えて,地盤内に過剰間隙水圧が発生し,洗掘の助長もしくは緩み領域を形成する可能性がある.本稿では,自由表面流れに起因して発生する,過剰間隙水圧の発生機構とその値を定量的に評価するため,移動床水路実験により地盤内の間隙水圧変動を詳細に観測した.さらに,自由表面流れにより誘発される移動床内の浸透流の速度分布を求め,その流速値を用いてBernoulliのエネルギー保存則から過剰間隙水圧を算出し,実験値と比較した.過剰間隙水圧の発生について理論値と実験値を比較したところ,自由表面流れに起因して地盤内に浸透流が発生し,流速差に伴って地盤表層では過剰間隙水圧が発生することを明らかとし,移動床極表層では,理論値と実験値は定量的に一致することを確認した.
  • 住友 慶三, 渡邊 康玄, 泉 典洋, 山口 里実, 横濱 秀明
    土木学会論文集B1(水工学) 72 4 I_751 - I_756 公益社団法人 土木学会 2016年 [査読無し][通常論文]
     
    &nbsp;The effect of the artificial flood to river channel disturbance is clarified quantitatively using the results of field observations and numerical simulations (iRIC Nays2D 4.2). The 1st viewpoint is maintenance of distributary leading to former watercourses which induces river channel disturbance at the time of a large flood. The 2nd viewpoint is a scale of river channel disturbance at the time of a large flood. The difference between the existence and non-existence of the artificial flood has been discussed. It was evaluated quantitatively that artificial flood is effective in maintenance of distributaries. Moreover, it was found quantitatively that the effect of mainstream alternation at bifurcations during a large flood which is expected by the maintenance of distributaries.
  • 角田 尭史, 泉 典洋, 横川 美和, 山田 朋人
    土木学会論文集B1(水工学) 72 4 I_739 - I_744 公益社団法人 土木学会 2016年 [査読無し][通常論文]
     
    The spiral troughs on Mars' polar ice caps are considered as cyclic steps formed on ice due to katabatic wind. Katabatic wind is a type of density current which flows downward pulled by gravity because of the denser air cooled by the ice floor. Due to the spatial non-uniformity of solidification of water vapor included in the air onto the ice floor, and sublimation of ice into the air, the boundary waves are formed on the ice floor. We performed laboratory experiments simulating the condition that katabatic wind blows on ice. Boundary waves were formed on the ice in the case that there was a large difference in temperature between the room air and the bottom of the ice.
  • Izumi Norihiro
    JOURNAL OF GEOGRAPHY-CHIGAKU ZASSHI 125 1 105 - 119 2016年 [査読有り][通常論文]
  • L. Zhang, G. Parker, C. P. Stark, T. Inoue, E. Viparelli, X. Fu, N. Izumi
    Earth Surface Dynamics 3 113 - 138 2015年02月 [査読有り][通常論文]
     
    The 1-D saltation-abrasion model of channel bedrock incision of Sklar and Dietrich (2004), in which the erosion rate is buffered by the surface area fraction of bedrock covered by alluvium, was a major advance over models that treat river erosion as a function of bed slope and drainage area. Their model is, however, limited because it calculates bed cover in terms of bedload sediment supply rather than local bedload transport. It implicitly assumes that as sediment supply from upstream changes, the transport rate adjusts instantaneously everywhere downstream to match. This assumption is not valid in general, and thus can give rise to unphysical consequences. Here we present a unified morphodynamic formulation of both channel incision and alluviation that specifically tracks the spatiotemporal variation in both bedload transport and alluvial thickness. It does so by relating the bedrock cover fraction to the ratio of alluvium thickness to bedrock macro-roughness, rather than to the ratio of bedload supply rate to capacity bedload transport. The new formulation (MRSAA) predicts waves of alluviation and rarification, in addition to bedrock erosion. Embedded in it are three physical processes: alluvial diffusion, fast downstream advection of alluvial disturbances, and slow upstream migration of incisional disturbances. Solutions of this formulation over a fixed bed are used to demonstrate the stripping of an initial alluvial cover, the emplacement of alluvial cover over an initially bare bed and the advection-diffusion of a sediment pulse over an alluvial bed. A solution for alluvial-incisional interaction in a channel with a basement undergoing net rock uplift shows how an impulsive increase in sediment supply can quickly and completely bury the bedrock under thick alluvium, thus blocking bedrock erosion. As the river responds to rock uplift or base level fall, the transition point separating an alluvial reach upstream from an alluvial-bedrock reach downstream migrates upstream in the form of a "hidden knickpoint". A tectonically more complex case of rock uplift subject to a localized zone of subsidence (graben) yields a steady-state solution that is not attainable with the original saltation-abrasion model. A solution for the case of bedrock-alluvial coevolution upstream of an alluviated river mouth illustrates how the bedrock surface can be progressively buried not far below the alluvium. Because the model tracks the spatiotemporal variation in both bedload transport and alluvial thickness, it is applicable to the study of the incisional response of a river subject to temporally varying sediment supply. It thus has the potential to capture the response of an alluvial-bedrock river to massive impulsive sediment inputs associated with landslides or debris flows.
  • 横川 美和, 京極 晃年, 泉 典洋
    土木学会論文集B1(水工学) 71 4 I_997 - I_1002 公益社団法人 土木学会 2015年 [査読無し][通常論文]
     
    In rivers in mountain areas, a series of steps are often observed on bedrock. They are thought to be cyclic steps formed due to erosion of bedrock, which should be driven by abrasion due to bedload sediment transport. We demonstrated a series of flume experiments of the formation of cyclic steps on bedrock by abrasion due to bedload transportation using weak mortar as the model bedrock. The shapes of cyclic steps are dependent on the sand feed rate under the water discharge of this experiment, i.e., a short upstream-facing slope and a long downstream facing slope for the lower sand feed rates, whereas long upstream-facing slope and a short and steep downstream facing slope for the higher sand feed rates. This result differ from our previous study, whose water discharge was lower and the shape of the steps was independent from the sand feed rate. In the case of higher discharge, sediment cover affects the location of vortices caused by the hydraulic jumps to make the short and steeper downstream facing slope.
  • 内藤 健介, 泉 典洋, 横川 美和, 角田 尭史
    土木学会論文集B1(水工学) 71 4 I_1027 - I_1032 公益社団法人 土木学会 2015年 [査読無し][通常論文]
     
    A linear stability analysis of interfacial instability induced by turbulent flow on the ice surface is performed by the use of the Reynolds-averaged Navier-Stokes equations incorporated with the mixing length turbulent model, the heat transfer equations in ice and flow,and the Stefan condition to describe the time evolution of the ice surface.It is found from the analysis that, if the outside air temperature is higher than the melting point and the ice bottom temperature is lower than the melting point, antidune-like boundary waves are formed on the ice surface while, if the outside air temperature is lower than the melting point,dune-like boundary waves are formed on theice surface.
  • UDDIN Md Jahir, 泉 典洋, 長谷川 和義, PORNPROMMIN Adichai
    土木学会論文集B1(水工学) 71 4 I_1021 - I_1026 公益社団法人 土木学会 2015年 [査読無し][通常論文]
     
    Linear stability analysis of the formation of fluvial sand bars with bank erosion is performed with the use of St.Venant shallow water equations and continuity equation, and a process-based bank erosion model. The process-based bank erosion model is derived from the integration of sediment continuity equation in the bank region. The time variation of bank locaion is proportional to the lateral sediment transport rate at the junction between bed and bank regions, which is evaluated by the lateral sediment transport rate in the bank region. and the time variation of the bed elevation at the junction. It is found from the analysis that quasi-meandering with the wavelength slightly shorter than bars takes place with the formation of bars in the range of moderately large aspect ratios.
  • 一瀬 輪子, 北野 慈和, 山田 朋人, 渡部 靖憲, 泉 典洋
    土木学会論文集G(環境) 71 5 I_289 - I_294 公益社団法人 土木学会 2015年 [査読無し][通常論文]
     
    中緯度地域における大気の振る舞いは,偏西風の蛇行及び高低気圧の移動によって大きく影響を受け,これは傾圧不安定波として解釈される.代表的な傾圧不安定波の室内実験手法としてFultzやHideが提唱した回転水槽実験が挙げられるが,本研究では底面から温度差を与える条件にて実験を行った.この条件では,地球における極域の流れの観察が可能であり,また傾圧不安定波の蛇行の振幅も制限されない.この手法を用いて実験を行ったところ,波数4-6程度の波動が観察され,流れ場は時間とともに動的に変化した.水槽の中心付近の渦度と東西(周方向)流速との間には,時間とともに同期する関係が見られた.
  • Takuya Inoue, Norihiro Izumi, Yasuyuki Shimizu, Gary Parker
    JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE 119 10 2123 - 2146 2014年10月 [査読有り][通常論文]
     
    A major control on bedrock incision is the interaction between alluvial cover and erosive mobile grains. The extent of alluvial cover is typically predicted as a function of relative sediment flux (sediment supply rate over bed load transport capacity, q(bs)/q(bc)), yet little is known about how the bed roughness affects the alluvial cover. We performed field experiments with various flow discharges, sediment supply rates, grain sizes, and bed surface topographies. We then developed physically based models for estimating the threshold of sediment movement and the extent of alluvial cover, so as to include the effect of roughness change. The results for the threshold of sediment movement and the extent of alluvial cover obtained from our models show reasonable agreement with the results of the field experiments. We explored the sensitivity of the models to variations in sediment supply and bedrock relative roughness (bedrock hydraulic roughness height over grain size, k(sb)/d). The results suggest the following: (1) a larger relative roughness yields a greater dimensionless critical shear stress required for initial sediment motion; (2) at a given sediment supply rate, the extent of alluvial cover is larger when the relative roughness is larger; (3) when the sediment supply rate and the relative roughness are small, throughput bed load moves over (and can abrade) a purely bedrock channel with no alluvial cover; and (4) the critical value of sediment supply rate below which throughput bed load transport occurs increases with decreasing relative roughness. The experimental results and analysis provide a framework for treating the (a) incisional morphodynamics of purely bedrock rivers by throughput bed load with no alluvial cover, (b) incisional/alluvial morphodynamics of mixed bedrock-alluvial rivers, and (c) purely alluvial morphodynamics, as well as the transition between these states.
  • A. C. Lima, N. Izumi
    PHYSICS OF FLUIDS 26 8 2014年08月 [査読有り][通常論文]
     
    A predictive theory is developed to investigate the nonlinear instability regime of perturbed shear layers in open-channel flows with lateral vegetation. The turbulence is characterized by two distinct scales: a sub-depth turbulence which is associated with the bed shear stress and a large-scale turbulence associated with the large horizontal eddies which develop in the shear layer. The sub-depth turbulence is modeled by assuming a logarithmic vertical distribution of the velocity. Meanwhile, an analogous model for the large-scale turbulence requires the estimation of the transverse velocity profile in the nonlinear state because the growth of the large-scale disturbances expands the shear layer and modifies the velocity distribution across the channel. The nonlinear growth of the disturbances is limited, however, because solid boundaries in the channel play stabilizing mechanisms which lock the amplitude of the large-scale disturbances into a finite-equilibrium state, for which a corresponding transverse velocity profile is determined. A weakly nonlinear stability analysis is performed and the results are validated using experimental data from previous works. (C) 2014 AIP Publishing LLC.
  • Adriano C. de Lima, Norihiro Izumi
    JOURNAL OF HYDRAULIC ENGINEERING 140 3 231 - 240 2014年03月 [査読有り][通常論文]
     
    A linear stability analysis of flow in an open-channel partially covered with vegetation was performed. The differential drag between vegetated zones and adjacent nonvegetated zones is known to induce a lateral gradient of the streamwise velocity. The velocity gradient may result in flow instability in the shear layer around the edge of the vegetated zone causing the generation of discrete horizontal vortices. We assume that the base state flow field before the occurrence of instability is characterized by turbulence with a smaller length scale than the flow depth, which is mainly generated by the bottom friction. By introducing perturbations to the flow depth as well as the streamwise and transverse velocities in the base state, the conditions required for perturbations to grow in time were studied over a wide range of (1)Froude number, (2)normalized nonvegetated zone width, and three other dimensionless parameters that represent the relative effect of (3)bed friction, (4)vegetation drag, and (5)subdepth eddy viscosity. All parameters were found to have positive and negative growth rates of perturbations within their respective evaluated ranges. The characteristic vortex shedding frequencies associated with the maximum growth rate was compared with those observed in experiments. Although the analysis that employs a base state set without the large scale lateral motions was shown to be capable of predicting the order of magnitude of the frequencies, there is a systematic discrepancy between the predicted and observed frequencies, which may be due to the limitation of linear stability analysis.
  • 泉 典洋, デリマ アドリアーノ, コーティニョ
    土木学会論文集A2(応用力学) 70 2 I_801 - I_806 公益社団法人 土木学会 2014年 [査読無し][通常論文]
     
    流れの安定性の問題は流体力学上の古典的問題の一つである.自由表面流の安定性についてもこれまで数多くの研究が行われているが,波数-Reynolds数平面上における擾乱の増幅率の正確な変化特性を明示した安定性ダイアグラムは未だ得られていない.本論文では,Orr-Sommerfeld方程式を自由表面流について適切な境界条件の下で数値的に解くことで詳細な安定性ダイアグラムを得た.それにより,2次元Poiseulle流れや平板境界層流れとは異なり,自由水面流れの不安定領域は複雑な形状を有していることが明らかとなった.
  • 井上 卓也, 松元 一馬, 清水 康行, 泉 典洋, Parker Gary, 伊藤 丹
    土木学会論文集A2(応用力学) 70 2 I_727 - I_734 公益社団法人 土木学会 2014年 [査読無し][通常論文]
     
    岩床河川の地形変化を把握する上で,岩床上の砂礫被覆面積の正確に予測することは必要不可欠である.最も簡易的なモデルにおいて,砂礫被覆の面積割合は給砂量と飽和流砂量の比に線形的に依存すると考えられている.しかし,自然岩床河川の粗度は様々であり,これが被覆率に大きな影響を与える可能性が高い.そこで,本研究では,給砂量・岩床粗度・被覆割合の関係について,実験的に分析を行った.<br>実験の結果,岩床粗度が大きいほど被覆割合も大きくなった.また,岩床粗度が砂礫床粗度(粒径程度)より粗い場合,被覆率は給砂量-飽和流砂量比に比例するが,その逆の場合,給砂量が飽和流砂量を超えるまで殆ど被覆は起こらず,超えた途端に急激に完全な砂礫床へ遷移することが明らかとなった.
  • 北野 慈和, 山田 朋人, 泉 典洋
    土木学会論文集B1(水工学) 70 4 I_871 - I_876 公益社団法人 土木学会 2014年 [査読無し][通常論文]
     
    Schmid & Henningson discussed the point disturbance in the homogeneous medium of piecewise linear boundary layer using the method of stationary phase. In addition to this study, we include the density profile to consider the inhomogeneous boundary layer like atmospheric boundary layer. We assume first that the fluid is inviscid and incompressible, density being convected but not diffused. Then the fundamental equations are the Navier-Stokes equations, continuity equation and incompressibility equation and we derive the 3-dimentional Taylor-Goldstein equation. Under the Boussinesq approximation, we obtain the exact solution about the point disturbance propagation on the arbitrary horizontal plane. Using internal Froude number, we explain the characteristics of the solutions.
  • 和田 萌実, 泉 典洋, 渡部 靖憲
    土木学会論文集B1(水工学) 70 4 I_1177 - I_1182 公益社団法人 土木学会 2014年 [査読無し][通常論文]
     
    On March 11, 2011, huge tsunamis took place due to the Great East Japan Earthquake as large as Mw 9.0. It has been observed that an ocean bottom presimeter (OBP) and an ocean bottom seismometer (OBS) were sagged to the deep ocean by approximately 1 km, which suggests the possibility of the generation of a large scale line-source turbudity current taking place on the ocean floor off the coast of Tohoku. In this study, we reproduce the tsunami by the use of a tsunami simulation software, iRIC/ELIMO, evaluate the entrainment rate of suspended sediment, and estimate the source area of the turbidity current. It is found, from the results of the analysis, that a large amount of entrainment continuously took place from the north of Oshika Peninsula to the area within 40 km off the coast of Sendai Bay, which is assumed to be the source area of the turbidity current.
  • 柳屋 圭吾, 柿沼 孝治, 武田 淳史, 泉 典洋
    土木学会論文集B1(水工学) 70 4 I_1363 - I_1368 公益社団法人 土木学会 2014年 [査読無し][通常論文]
     
    Vegetation in rivers causes serious problems such as increases in flood risk due to water level rise during flood. Salicaceae trees are dominant on flood plains and sand bars of rivers in cold and snowy Hokkaido. Therefore, it is crucially important to inhibit the growth of salicaceae trees for river management. While there is a problem that salicaceae trees are flourishing in the Satsunai River, one plant species in the family salicaceae, chosenia arbutifolia, is losing its habitat. Chosenia arbutifolia is registered in the red data book of Japan. Hokkaido Development Bureau, the management authority, is performing field experiments to sweep away young salicaceae, and to form fluvial bars covered with gravel by artificial flash flood with the use of snow melting water released from Satsunaigawa Dam. Authors studied the habitat situations of young salicaceae and chosenia arbutifolia before and after an artificial flash flood, and relations between hydraulic conditions and habitat of the plants.
  • Kazuno Arai, Hajime Naruse, Ryo Miura, Kiichiro Kawamura, Ryota Hino, Yoshihiro Ito, Daisuke Inazu, Miwa Yokokawa, Norihiro Izumi, Masafumi Murayama, Takafumi Kasaya
    GEOLOGY 41 11 1195 - 1198 2013年11月 [査読有り][通常論文]
     
    We show the first real-time record of a turbidity current associated with a great earthquake, the Mw 9.0, 2011 Tohoku-Oki event offshore Japan. Turbidity current deposits (turbidites) have been used to estimate earthquake recurrence intervals from geologic records. Until now, however, there has been no direct evidence for large-scale earthquakes in subduction plate margins. After the 2011 Tohoku-Oki earthquake and tsunami, an anomalous event on the seafloor consistent with a turbidity current was recorded by ocean-bottom pressure recorders and seismometers deployed off Sendai, Japan. Freshly emplaced turbidites were collected from a wide area of seafloor off the Tohoku coastal region. We analyzed these measurements and sedimentary records to determine conditions of the modern tsunamigenic turbidity current. We anticipate our discovery to be a starting point for more detailed characterization of modern tsunamigenic turbidites, and for the identification of tsunamigenic turbidites in geologic records.
  • Endo Noritaka, Takashi Murakami, Izumi Norihiro
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 82 3 2013年03月 [査読有り][通常論文]
  • 横川 美和, 泉 典洋, 内藤 健介
    土木学会論文集B1 57 4 1_1129 - 1134 土木学会 2013年 [査読無し][通常論文]
  • 内藤 健介, 泉 典洋, 横川 美和
    土木学会論文集B1 57 4 1_1123 - 1128 土木学会 2013年 [査読無し][通常論文]
  • 泉 典洋, 横川 美和, 内藤 健介
    土木学会論文集B1 57 1_1117 - 1122 土木学会 2013年 [査読無し][通常論文]
  • 田中 岳, 泉 典洋
    土木学会論文集B1 (水工学) 57 1_1033 - 1038 土木学会 2013年 [査読無し][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 I_51 - I_55 公益社団法人 土木学会 2013年 [査読無し][通常論文]
     
    This paper presents vorticity instabilities occurring during wave breaking process, which interprets formations of the initial three-dimensional vortex structure, scarifying and fingering surface via surface-vorticity interactions, and the sea-spray fragmenting from the finger jets. Three-dimensional linear instability analyses are performed for identifying these instability modes to describe a series of local surface deformations featuring the splashing process in this study.
  • 泉 典洋, 前田健一
    土木学会論文集A2(応用力学) 69 2 I_545 - I_551 公益社団法人 土木学会 2013年 [査読無し][通常論文]
     
    When rain pours over porous media, rain water tends to infiltrate their inside. In order to enable further infiltration, the air in the void of porous media has to be replaced with water. If the replacement between water and air is not smoothly implemented, water cannot seep into porous media as observed on river levees during heavy rainfall. This might be caused by the fact that the equilibrium of water with a relatively high density on top of air with a far lower density may be stable or weakly unstable in porous media. We have performed a linear stability analysis to study the Rayleigh-Taylor instability in porous media.
  • 横川 美和, 泉 典洋, 内藤 健介, 山田 朋人, GREVE Ralf
    土木学会論文集B1(水工学) 69 4 I_1129 - I_1134 公益社団法人 土木学会 2013年 [査読無し][通常論文]
     
    The spiral troughs observed on the surface of Mars' north polar ice cap show upstream-migrating structures, which indicate that those may possibly be cyclic steps formed by a density current created by cooling of the atmosphere due to the ice. It can be useful to estimate the formative process of the Mars' polar ice cap and thus the climatic history of Mars using the analogues of cyclic steps on the Earth. In this study, we have performed a series of physical experiments aimed at the formation of cyclic steps on ice by flowing fluid. Temperature distribution plays a quite important role for the formation and development of step topography on the ice surface, and was set as ice &lsaquo; fluid &lsaquo; ambient air in this experiment. As a result, step topography was formed on the ice except the case whose Fr is lowest, i.e., 0.76, and the steps generally developed upstream direction. The results of the present experiment agree with the mathematical model describing the evolution of the ice surface by flowing fluid.
  • 内藤 健介, 泉 典洋, 横川 美和, 山田 朋人
    土木学会論文集B1(水工学) 69 4 I_1123 - I_1128 公益社団法人 土木学会 2013年 [査読無し][通常論文]
     
    In recent years, cyclic steps are discovered in a variety of environments, such as deep ocean floors and ice floors on planets other than the earth. Water can exists only in the form of ice in the extraterrestrial environments, where temperature is commonly by far lower than that on the earth. Therefore, cyclic steps in the extraterrestrial environments are expected to be often found on ice. In order to obtain basic knowledge on the formation of ice steps, we have performed a series of experiments in a cold room of Institute of Low Temperature Science, Hokkaido University, and reproduced ice steps migrating in the downstream direction. In this paper, we formulated the formation process of ice steps, and provide a reasonable explanation of the downstream migrating ice steps based on the experimental results.
  • 泉 典洋, 横川 美和, 内藤 健介
    土木学会論文集B1(水工学) 69 4 I_1117 - I_1122 公益社団法人 土木学会 2013年 [査読無し][通常論文]
     
    Periodic boundary waves are sometimes observed on surfaces of large ice bodies such as glaciers and polar ice caps on Mars as well as on the Earth. These boundary waves may be formed by boundary instability between the ice surface and the fluid flowing on it. We propose a mathematical model to describe the evolution of the ice surface by the use of the Navier-Stokes equations, the heat transfer equations of flow and ice, and a heat balance equation at the boundary. Assuming that the temperature above the flow is higher than that below the ice, we perform a linear stability analysis, and obtained the results that the flow-ice boundary becomes unstable in the range of large Reynolds numbers, and the boundary waves migrate upstream in this temperature condition.
  • 田中 岳, 泉 典洋
    土木学会論文集B1(水工学) 69 4 I_1033 - I_1038 公益社団法人 土木学会 2013年 [査読無し][通常論文]
     
    Riverbed degradation occurs in many rivers in the world. It causes serious problems in river management. For example, the bedrock which had been covered with gravels is exposed due to the riverbed degradation, which destabilizes river structures, such as bank revetment works and groundsill works. In this study, hydraulic experiments were performed to determine sediment transport characteristics on bedrock channels partly covered with gravels. We obtained the following results. The bedload transport rate and the friction coefficient can be related with the coverage rate of gravels on the channel bed. A simple mathematical model describing sediment behavior on bedrock channels was proposed.
  • 泉 典洋, 青木 章宜
    土木学会論文集A2(応用力学) 68 2 I_609 - I_616 公益社団法人 土木学会 2012年 [査読無し][通常論文]
     
    It is commonly observed that river channels become unstable to shift their courses repeatedly particularly when bed aggradation is taking place. On the contrary, river channels are stable and maintain their courses under bed degradation. We study the effect of bed aggradation and degradation on stability of river channels. We perform linear stability analysis of channel meander taking account of gradual bed aggradation and degradation. It is found from the analysis that bed aggradation decreases stability of channels and induce channel meandering while bed degradation stabilize channels and inhibit channel meandering.
  • 泉 典洋, 横川 美和, パーカー ゲイリー
    土木学会論文集B1(水工学) 68 4 I_955 - I_960 公益社団法人 土木学会 2012年 [査読無し][通常論文]
     
    In rivers located in mountain areas, a series of steps are often observed to be formed on bedrock. This is called cyclic steps formed by bedrock incision. This study proposes a simplified model for describing the erosion process by abrasion due to bedload, and obtain an equilibrium step shape migrating upstream without changing its shape. It is found that there are three important parameters: the threshold velocity Ut for bedload, the availability function at the Froude critical point pc, and the average slope. Once these three parameters are given, the wavelength L, the erosion rate averaged over one step length En, and the water and bed surface profiles are determined. It is found that qualitative features of steps observed in experiments are well described by the analysis.
  • 北野 慈和, 山田 朋人, 泉 典洋
    土木学会論文集G(環境) 68 5 I_205 - I_210 公益社団法人 土木学会 2012年 [査読無し][通常論文]
     
    日本の豪雨イベントを引き起こすメソスケールの現象の一つとして線状降水帯が挙げられるが,その物理機構については不明な点が多い。線状降水帯の形成過程を解明することは防災の観点から非常に重要である。そこで本研究では,線状降水帯が発生する条件の一つである不安定な成層をした大気場の空間特性を解析的に明らかにした。解析では,問題を単純化するために降水や熱力学的な効果は考えず,大気場における鉛直方向の擾乱の水平分布のみを考慮している。この解析により擾乱の発達とフルード数及び密度差に関する無次元パラメータとの関係が明らかとなり,これらと線状降水帯との関係性について考察した。
  • 小松 佑輔, 渡邊 康玄, 泉 典洋, 竹林 洋史, KOMATU Yuusuke, WTANABE Yasuharu, IZUMI Norihiro, TAKEBAYASHI Hiroshi
    河川技術論文集 17 167 - 172 公益社団法人 土木学会 2011年07月 [査読有り][通常論文]
  • DE LIMA Adriano Coutinho, IZUMI Norihiro
    土木学会論文集B1(水工学) 55 ROMBUNNO.32  2011年02月 [査読無し][通常論文]
  • WUBNEH Atinkut Mezgebu, IZUMI Norihiro
    土木学会論文集B1(水工学) 67 4 S-127-S-132  2011年02月 [査読無し][通常論文]
  • DIAS Duleeka Dahampriya, IZUMI Norihiro, YOKOKAWA Miwa
    土木学会論文集 A2(応用力学)(Web) 67 2 I_503 - I_510 2011年 [査読無し][通常論文]
  • 平塚 智史, 泉 典洋
    土木学会論文集A2(応用力学) 67 2 I_671 - I_682 公益社団法人 土木学会 2011年 [査読無し][通常論文]
     
    There have been a large number of studies on bed waves in rivers. It has been known that bed waves are strongly related to the Froude number. Meanwhile, there are only few studies on waves formed at the boundary between flowing water and erodible beds in closed conduits without free water surfaces. In order to predict the flow resistance of closed conduits such as sediment bypass tunnels and ice-covered rivers, it is important to obtain detailed information on the formation of boundary waves. Seki and Izumi<sup>2)</sup> have proposed a linear stability analysis to explain the formation of small scale boundary waves in closed conduits. They have also reproduced small scale boundary waves in flume experiments, and compared with their analysis. According to their analysis, the Shields and Euler numbers are the dominant parameters, and the flat bed becomes unstable when the Euler number becomes larger than the critical Euler number, which increases with the Shields number. However, the agreement between the prediction and their observation is not sufficiently good. In this study, we introduce the ratio of the shear velocities between the lower and upper walls as a new parameter, and improve the agreement. In addition, we perform a weakly nonlinear stability analysis to obtain more detailed information on behavior of boundary waves in the vicinity of the critical Euler number. We find that the transition between flat bed and boundary wave regimes in closed conduits is characterized by subcritical bifurcation.
  • 高畑 知明, 泉 典洋
    土木学会論文集A2(応用力学) 67 2 I_661 - I_669 公益社団法人 土木学会 2011年 [査読無し][通常論文]
     
    Bed slope changes due to bed aggradation/degradation caused by an increase/decrease of sediment supply. Though we have performed a linear stability analysis of sand bars incorporating effects of bed aggradation/degradation, the analysis has assumed bed elevation changes without changing its shape, and temporal variation of bed slope has not been taken into account. In order to study bar instability with temporal variation of bed slope, the WKB method is applied with the use of the rate of bed slope changes as a small parameter. The analysis shows that, unstable regions in the instability diagram is expanded to the range of large wavenumbers when bed slope decreases while unstable regions are reduced when bed slope increases.
  • 竹井 義博, 泉 典洋
    土木学会論文集A2(応用力学) 67 2 I_511 - I_519 公益社団法人 土木学会 2011年 [査読無し][通常論文]
     
    Overland and seepage flows have been hypothesized as dominant factors in the initiation and evolution of gullies and channels. Many studies on channelization due to erosion by overland flow have been carried out whereas only few studies have focused on seepage erosion. This study aims to acquire fundamental knowledge on the seepage erosion from experiments and a linear stability analysis. We use the Dupuit-Forchheimer equation and a description of the retreat of the seepage front. The retreat speed consists of two terms: the first is assumed to be a power law function of a specific discharge at the front exceeding a critical discharge, and the second is assumed to be a diffusion-like function of front shapes, in which the retreat speed is enhanced and retarted by the convexity and concavity of fronts, respectively. We find that the characteristic channel spacing becomes infinitely small when the effect of the front shapes is excluded. We conduct a series of experiments with various depth of sediment layers and chamber slopes in order to estimate the diffusion-like coefficient. We find that the width of gullies increases with increasing grain size and bed gradient, while channel spacing decreases. We propose a relationship between the diffusion-like coefficient and the combination of the two functions, water level at the seepage front and weight of a failure block.
  • 高畑 知明, 泉 典洋
    土木学会論文集B1(水工学) 67 4 S_865-S_870 - I_870 公益社団法人 土木学会 2011年 [査読無し][通常論文]
     
    In the existing linear stability analysis of fluvial bars, it is assumed that the river bed is in equilibrium, and the bed slope and flow are uniform in the streamwise direction. Though it is generally said that the bed becomes more unstable under bed aggradation, and becomes more stable under bed degradation, the existing analysis cannot shed further light on their effects. In this paper, linear stability analysis incorporating weakly non-equilibrium processes of bed aggradation/degradaion is performed by the use of the WKBJ method in order to clarify their effects. Bed aggradation or degradation is assumed to be sufficiently slow compared with the bed evolution due to instability, and its non-dimensional speed is used as a small parameter. The analysis explains that river beds become stable and sand bars tend not to be formed under degradation, and that river beds become unstable under aggradation. In addition, alternate bars are more strongly affected by bed aggradation/degradation than multiple bars.
  • A. C. Lima, N. Izumi
    13TH EUROPEAN TURBULENCE CONFERENCE (ETC13): INSTABILITY, TRANSITION, GRID TURBULENCE AND JETS 318 2011年 [査読有り][通常論文]
     
    The turbulent flow in a wide rectangular open channel partially covered with vegetation is studied using linear stability analysis. In the base state normal flow condition, the water depth is constant and the transverse velocity vanishes, while there is a lateral gradient in the streamwise velocity with an inflexion point at the boundary between the vegetated zone and the main channel. The Reynolds stress is expressed by introducing the eddy viscosity, which is obtained from assuming a logarithmic distribution of the velocity near the bed. Perturbation expansions are introduced to the streamwise and transverse velocities, as well as to the water depth. The system of governing equations was solved in order to determine the maximum growth rate of the perturbations as a function of parameters which describe physical characteristics of the channel and the flow.
  • A. Pornprommin, N. Izumi
    JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE 115 doi: 10.1029/2009JF001369  2010年06月 [査読有り][通常論文]
     
    Because seepage erosion is generated by complex interactions with other processes, associated stream incision process is not well understood. In this study, some fundamental characteristics of incipient incision by seepage erosion were investigated by laboratory experiments and linear stability analysis. The experiments were conducted with various sediment layer depths and gradients. With similar discharges in the experiments, incision spacing decreases with increasing depth of the sediment layer and with increasing gradient, whereas incision width increases with increasing sediment layer depth. A linear stability analysis was performed using the Dupuit-Forchheimer equation and an expression of the planimetric retreat of the scarp. The retreat velocity of the scarp consists of two terms: (1) a power law function that describes the specific discharge in excess of a critical discharge and (2) a diffusion-like function that describes the incision edge shapes, in which the retreat rate is enhanced or reduced by the convexity and concavity of the edges, respectively. This analysis shows that the characteristic incision spacing becomes infinitely small when the effect of the edge shapes is excluded. Using the experimental data of incision spacings, the values of the diffusion-like coefficient in the second term were estimated. Since the weight of a failure block and hydraulic pressure are the driving forces in the slope stability analysis, a relationship was found between the diffusion-like coefficient and the combination of the two forces.
  • Adichai Pornprommin, Yoshihiro Takei, Atinkut Mezgebu Wubneh, Norihiro Izumi
    JOURNAL OF HYDRO-ENVIRONMENT RESEARCH 3 4 232 - 238 2010年03月 [査読有り][通常論文]
     
    This study presents a series of systematic experiments on channelization by seepage erosion with various sediment layer depths and chamber slopes. When the depth of the sediment layer increases, the threshold discharge for channel initiation decreases, but the channel width increases. This is due to the fact that an increase in the weight of sediment induces an increase in a gravitational driving force along the chamber bed. When the chamber slope increases, we also found a similar effect as an increase in the sediment layer depth that the threshold discharge decreases, but the width increases. While channel bifurcation was never found in the previous study using plastic pellets as sediment, it was observed in many experiments in the present study, in which very coarse sand was used. We hypothesized that the characteristics of groundwater flow field and the resistibility of sediment material to slope failure play important roles on the channel bifurcation. (C) 2009 International Association for Hydro-environment Engineering and Research, Asia Pacific Division. Published by Elsevier B.V. All rights reserved.
  • 平塚智史, 泉典洋, 関陽平
    水工学論文集 54 151 - 156 2010年02月 [査読有り][通常論文]
  • WUBNEH Atinkut Mezgebu, PORNPROMMIN Adichai, IZUMI Norihiro, NAGAHARA Junya
    水工学論文集 54 151 - 156 2010年02月 [査読無し][通常論文]
  • 竹井義博, アディチャイ ポンプロミン, N. Izumi
    応用力学論文集 13 883 - 888 2010年 [査読有り][通常論文]
  • PORNPROMMIN Adichai, IZUMI Norihiro
    応用力学論文集 13 877 - 882 2010年 [査読有り][通常論文]
  • PORNPROMMIN Adichai, TAKEI Yoshihiro, WUBNEH Atinkut Mezgebu, IZUMI Norihiro
    応用力学論文集 12 887 - 894 2009年08月 [査読有り][通常論文]
  • 泉 典洋, Gary Parker
    水工学論文集 53 139 - 144 2009年02月 [査読有り][通常論文]
  • PORNPROMMIN Adichai, IZUMI Norihiro
    水工学論文集 53 139 - 144 2009年02月 [査読無し][通常論文]
  • PORNPROMMIN A, IZUMI N, TSUJIMOTO T
    Journal of Geophysical Research 114 F01032 doi:10.1029/2008JF001034  2009年 [査読有り][通常論文]
  • Theoretical analysis for the interaction between the river flow and the seepage flow
    Rathnayake Upaka, Izumi Norihiro
    RECENT ADVANCES IN FLUID MECHANICS 46 - 51 2009年 [査読有り][通常論文]
  • Pornprommin Adichai, Norihiro Izumi
    応用力学論文集 11 709 - 717 土木学会 2008年 [査読有り][通常論文]
  • 泉 典洋, 佐藤 博重
    応用力学論文集 11 851 - 857 公益社団法人 土木学会 2008年 [査読有り][通常論文]
     
    The effect of pressure gradient on the dune-flat bed transition is studied in terms of linear and weakly nonlinear stability analysis. We employ the Kovacs & Parker bedload transport formula extended to incorporate the effect of pressure gradient on the lee side of dunes proposed by Yamaguchi & Izumi.The linear anlysis reveals that the critical Froude number is slightly increased due to the effect of pressure gradient. The nonlinear stability analysis reveals that the effect of pressure gradient renders the bifurcation pattern at the dune-flat bed transition subcritical in the range of relatively large resistance coefficients.
  • 関 陽平, 泉 典洋
    応用力学論文集 11 753 - 760 公益社団法人 土木学会 2008年 [査読有り][通常論文]
     
    It is commonly known that the flat bed is unstable in open channels in the range of small and large Froude numbers, in which the presence of the free water surface is important to the instability. However, instability of the flat bed without free water surface has not been well understood. In this study, we perform a linear stability analysis of the boundary between sediment and water in pipes transporting sediment with the use of the mixing length turbulent model. The analysis reveals that the governing parameter is the Euler number, and that the boundary is unstable in the range of relatively small Euler numbers.
  • 中里 遥介, 泉 典洋
    応用力学論文集 11 727 - 734 公益社団法人 土木学会 2008年 [査読有り][通常論文]
     
    Small-scale fluvial bed waves such as dunes and antidunes formed on river beds during floods increase the bed resistance, causing rises in water levels. Therefore, it is important to obtain detailed information on the conditions for the formation of bed waves. One of the purposes of this study is to extend the existing linear stability analysis of the formation of small-scale bed waves to the case with active suspended sediment transport. The analysis reveals that the critical Froude number for the formation of dunes is reduced, and the dune formation tends to be inhibited with increasing suspended sediment load.
  • 山口里実, 泉典洋
    水工学論文集 51 1015 - 1020 2007年02月 [査読有り][通常論文]
  • 山口 健治, 泉 典洋
    応用力学論文集 10 865 - 872 公益社団法人 土木学会 2007年 [査読有り][通常論文]
     
    Patterns of parallel submarine gullies with regular transverse spacing are observed at continental margins. These gullies are thought to be formed by turbidity currents. In this study, the existing model is extended to more general cases in which the slope profile is arbitrary and the entrainment of fresh seawater cannot be neglected. A linear stability analysis is performed with the use of the layer-averaged momentum and continuity equations of turbidity currents, a dispersion equation of suspended sediment, and the Exner equation extended for the seabed subject to erosion and deposition due to turbidity currents. The analysis shows that the dominant spacing of submarine gullies on slopes with arbitrary shapes is of the order of 800-1600 times the Richardson-critical layer thickness of turbidity currents.
  • 大友 裕隆, 泉 典洋
    応用力学論文集 10 833 - 838 公益社団法人 土木学会 2007年 [査読有り][通常論文]
     
    The instability of water flow has been studied by a large number of researchers from a variety of points of view for a long time. In this study, a linear stability analysis is performed with the use of the Reynolds averaged Navier-Stokes equations and Darcy's law extended to more general cases in order to investigate the instability of flow on permeable river beds, and resulting water exchange between flowing water in rivers and seepage water beneath flat river beds. The spectral collocation method incorporated with the Chebyshev polynomials is employed in order to perform numerical solution of perturbed equations. It is found from the analysis that, in the case of permeable beds, flow becomes unstable in the range of small Froude numbers where flow is stable in the case of impermeable beds.
  • 泉 典洋, 長谷川 和義
    水工学論文集 51 1021 - 1026 公益社団法人 土木学会 2007年 [査読有り][通常論文]
     
    Weakly nonlinear stability analysis of fluvial dunes is performed with the use of the growth rate expansion method incorporated with the multiple scale parturbation technique. Open channel flow is modeled by the mixing length turbulent model. A series of perturbation equations are solved by the use of spectral collocation method with Chebyshev polynomial. The analysis reveals that the dune-flat bed transition is characterized by subcritical bifurcation when the resistant coefficient C<SUP>-</SUP><SUP>1</SUP> is large.
  • N Izumi, K Fujii
    JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE 111 F1 doi:10.1029/2005JF000345  2006年02月 [査読有り][通常論文]
     
    In this paper, we present a mathematical model of the formation of gullies at the downstream end of plateaus composed of weakly cohesive fine material such as freshly deposited volcanic ash as an extension of the theory of channel inception on purely erosional slopes proposed by Izumi and Parker (2000). We perform a linear stability analysis using the momentum equations of flow, the transport equation of suspended sediment, and the Exner equation for beds subject to both erosion and deposition of bed material. We find from the analysis that deposition leads to uniform growth of perturbations at small wave numbers (or large wavelengths) and suppresses the dominant wavelength associated with the maximum growth rate. When the effect of deposition increases further, channel initiation itself tends to be inhibited. As long as the effect of deposition is not large, slopes become unstable to transverse perturbations, and the dominant wavelength appears in the range of 6-15 times the Froude critical depth of the sheet flow on slopes, divided by the bottom friction coefficient. Assuming that the bottom friction coefficient is of the order of 0.01, we find that the dominant gully spacing is of the order of 1000 times the Froude critical depth, which is similar to the result obtained in the case without deposition. We find that deposition affects channel initiation itself rather than channel spacing.
  • 水嶋 大樹, 泉 典洋
    水工学論文集 50 1051 - 1056 公益社団法人 土木学会 2006年02月 [査読有り][通常論文]
     
    Surface flow produced by heavy rainfall concentrates on local troughs, resulting in further erosion of troughs and the formation of gullies. In the development process of gullies, a great amount of soil runs off. In this study, long-term changes of topography around gullies formed on Soya Hill are analysed with the of present and old topographical maps. In the analysis, detailed processes of gully development are revealed, and the annual average sediment yield is estimated to be 60 mm/year. We also conduct a field observation of a gully and a field survey around the gully head. It is found that the channel head is in the precess of spliting into three branches.
  • 泉 典洋, 山口 里実
    土木学会論文集B 62 4 360 - 375 公益社団法人 土木学会 2006年 [査読有り][通常論文]
     
    水位-流量曲線に見られるヒステリシス現象や単一水理条件下における河床形態の多価性がデューン-平坦床遷移時に生じる亜臨界分岐に起因する可能性を,著者らは弱非線形解析を用いて明らかにしている(以降,前報と呼ぶ).本研究は,前報で用いられていた近似解法を用いずに同様の解析を行うと同時に,フルード数とシールズ数の依存関係を適切に導入し分岐パラメータとしてのフルード数を再定義することにより,実験結果の意味を再評価し理論の再検証を行ったものである.解析の結果,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で特徴付けられることが明らかとなった.また流速係数が大きい領域における河床形態の多価性について実験結果は解析結果を裏付けることが示された.
  • 高橋 元気, 田中 仁, 松冨 英夫, 泉 典洋
    海洋開発論文集 22 451 - 456 公益社団法人 土木学会 2006年 [査読有り][通常論文]
     
    Old maps, such as <I>Inoh Maps</I> and other historical ones, are prospective which might be used for determining the changes of coastal geographical features in the past. It is expected that long-term geographical changes can be known provided that the accuracy of an old map is satisfactorily high. In the present study, the changes of geographical features in Nobiru Coast, Miyagi Prefecture and Matsukawaura Lagoon, Fukushima Prefecture are examined by comparing historical and latest maps. Furthermore, long-term sediment budget analysis is carried out for the Nobiru Coast.
  • 山口 健治, 泉 典洋
    応用力学論文集 9 925 - 932 公益社団法人 土木学会 2006年 [査読有り][通常論文]
     
    A mathematical model of turbidity currents flowing down from continental shelves to continental slopes is presented in this study. The layer-averaged momentum and continuity equations of turbidity currents, and the dispersion equation of suspended sediment are integrated with the use of a regularity condition satisfied at the Richardson critical point between continental shelves and continental slopes. The results of the analysis show that steady turbidity currents flowing from continental shelves to continental slopes can be realized only when the critical layer thickness is smaller than a certain value. It is also found that turbidity currents are mildly accelerated on continental slopes while turbidity currents are decelerated on continental shelves in the downstream direction. These results suggest that only turbidity currents with sufficiently large suspended concentration can reach the Richardson critical point, and that turbidity currents flowing from continental shelves to continental slopes have to be generated somewhere not far upstream from the Richardson critical point.
  • 大友 裕隆, 泉 典洋
    応用力学論文集 9 893 - 900 公益社団法人 土木学会 2006年 [査読有り][通常論文]
     
    The instability of shallow water flow has been studied by a large number of researchers from a variety of viewpoints since a long time ago. It has been found from linear stability analysis that, when the Froude number is large, uniform flow becomes unstable, resulting in the evolution of a train of waves, which are called roll waves. In this study, a linear stability analysis is performed with the use of the Reynolds averaged Navier-Stokes equations and the Darcy's equation extended in order to investigate the instability of flow on permeable river beds. From the analysis, we conclude that the stability of the flow becomes unstable when the wavenumber is from 0.02 to 0.2 and high Froude number. Furthermore, it is found that flow becomes unstable in the range of wavenumber from 0.02 to 0.2 with decreasing permeable layer thickness and with increasing permeation.
  • 泉 典洋, PORNPROMMIN Adichai, 辻本 哲郎
    土木学会論文集B 62 1 65 - 79 公益社団法人 土木学会 2006年 [査読有り][通常論文]
     
    従来の水路群発生の理論では,正式な線形安定解析を可能とするために,形状を変化させずに斜面上流方向に移動する自己保存型の斜面を基準状態として仮定していた.しかし実際には,水路化は様々な形状の斜面で観察される.本研究は,凍結時間近似と瞬間的安定性の概念を用いることによって,従来の理論<sup>1),2),3)</sup>を任意形状を有する斜面に拡張したものである.理論より,任意形状の斜面でもフルード限界点近傍の曲率が適当な範囲にあれば,従来の理論と同様に限界水深の1000倍程度の間隔で水路群が形成されることが明らかとなった.またフルード限界点近傍における曲率が小さくなると,侵食が卓越する場合,擾乱の成長率は減少し卓越波長は若干増加するが,堆積を無視できない場合,擾乱の成長率は大きくなるものの明確な卓越波長が現れなくなる.
  • 山口里実, 泉典洋
    土木学会論文集 796 53 - 67 公益社団法人 土木学会 2005年08月 [査読有り][通常論文]
     
    洪水時, 流量の小さい領域で発生したデューンは, 流量増加に伴って消滅し, 流量減少時に再形成される. その際, デューン河床から平坦床へ遷移する際の流量が, 平坦床からデューン河床に遷移する際の流量と比較して大きいヒステリシス現象が観察されている. 著者らは弱非線形安定解析の手法を用いて, ヒステリシス現象の原因の一つが, デューン―平坦床遷移過程に見られる亜臨界分岐である可能性を理論的に示した. しかしその際, 理論で予測される臨界フルード数が, 実河川で観測されるフルード数よりかなり大きくなることがわかっている. 本研究は, 浮遊砂の影響を取り入れた非線形安定解析を行うことによって, 浮遊砂が生じる条件下では臨界フルード数が減少するものの, やはり解の分岐形態は亜臨界分岐であることを理論的に明らかにする.
  • 泉 典洋
    水工学論文集 49 979 - 984 公益社団法人 土木学会 2005年 [査読有り][通常論文]
     
    Channels are commonly observed to develope upstream due to the concentration of flow and the resultant intensification of erosion around their channel heads. In the developing process, a channel head sometimes splits into two or more than two branches. By repeating such bifurcation, simple patterns of channels evolve into comlex patterns of channel networks. In this study, a mathematical model of channel bifurcation is presented in terms of the secondary instability of a channel head. Linear stability analysis is performed to study the instability of a hole in a horizontal plane imitating a channel head. It is found that a channel head becomes unstable for perturbation and chanel bifurcation is initiated when the critical depth divided by the friction coefficient is reduced compared with the channel radius.
  • 山口 里実, 泉 典洋
    水工学論文集 49 937 - 942 公益社団法人 土木学会 2005年 [査読有り][通常論文]
     
    In order to enable accurate predictions of the bedform change in rivers, the accurate estimation of the sediment transport rate is important. In this study, we propose a bedload formula taking into account the effect of the pressure gradient in flow caused by the formation of dunes on the basis of Kovacs & Parker's formula including the effect of the local bed inclination. We performed a nonlinear stability analysis by the use of the sediment transport formula derived in this study. It is found that the transition between dune-covered and flat bed transition is charactrized by subcritical bifurcation even if the effect of the local bed inclination is large.
  • 泉 典洋, ピライラー シタン, 田中 仁
    水工学論文集 49 907 - 912 公益社団法人 土木学会 2005年 [査読有り][通常論文]
     
    The understanding of the transport process of suspended fine particles in rivers becomes important from a viewpoint of biological environment in rivers. In this study, we propose a new transport model of suspended fine particles in rivers considering the availability of fine sediment on the bed. An availability function of fine sediment on the bed is introduced to take into account the reduction of the entrainment rate through lack of fine sediment on the bed. In a sample calculation with the assumption that the flow is in the unsteady normal flow condition, it is shown that the model can delineate an important fact that the SS concentration increases only up to some limit even if the bed shear stress increases. In addition, we applied the model to a field observation and show that the model can describe an important feature that the SS concentration is higher at the begining of a flood and decreases afterward despite large discharge.
  • 田中 仁, 松冨 英夫, 泉 典洋
    海岸工学論文集 52 556 - 560 公益社団法人 土木学会 2005年 [査読有り][通常論文]
     
    伊能図は今から約200年ほど前に伊能忠敬により作成され, 我が国全域を網羅する我が国初の本格的な地図として現在でも大きな関心を集めている. 伊能図に関してはこれまで人文地理の視点から注目を集めることが多かったが, その精度が定量的検討に耐えうるほど十分であれば, 海岸地形・河川地形の研究分野においても, 200年以上も前の地形情報を与えるものとして貴重な存在であると期待される. 本研究では, 阿武隈川や北上川といった比較的大規模な河川が流入している仙台海岸, 石巻海岸を対象とし, 伊能図 (大図) に描かれた海岸地形について, 現在のそれとの相違に着目して考察を行った.
  • 大友 裕隆, 泉 典洋
    応用力学論文集 8 813 - 820 公益社団法人 土木学会 2005年 [査読有り][通常論文]
     
    The instability of shallow water flow has been studied since a long time ago. It has been found from linear stability analysis that, when the Froude number is larger than approximately two, uniform flow becomes unstable, resulting in the evolution of a terrain of waves, which are called roll waves. In this study, a linear stability analysis is performed with the use of the shallow water equation extended for flow on permeable beds in order to investigate the instability of flow on permeable river beds and the resulting water exchange between river flow and the seepage flow beneath the beds. The analysis reveals that flow is unstable in the range of sufficiently large wavenumbers and Froude numbers when the permeable layer is sufficiently thicker than the flow on the bed. In the range of instability, water exchange between river flow and the hyporheic layer beneath river beds is expected to be activated.
  • N Izumi
    JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 109 C3 2004年03月 [査読有り][通常論文]
     
    [1] A mathematical model of the formation of submarine gullies due to turbidity currents is presented in this study. A linear stability analysis is performed with the use of layer-averaged momentum equations of turbidity currents, a dispersion equation of suspended sediment, and the Exner equation extended for the seabed subject to erosion and deposition due to turbidity currents. The analysis shows that the dominant gully spacing is of the order of 1500 - 8000 times the Richardson-critical layer thickness of turbidity currents. Evaluating the Richardson-critical layer thickness to be of the order of 0.1 - 1.0 m, the spacing of submarine gullies is of the order of 150 - 8000 m. According to observations, the spacing of submarine gullies ranges from a few hundred meters to a few kilometers. The theoretical results are found to be consistent with the observations.
  • PORNPROMMIN A, IZUMI N, TSUJIMOTO T
    水工学論文集 48 2 1009 - 1014 2004年02月 [査読有り][通常論文]
  • PILAILAR S, SAKAMAKI T, HARA Y, IZUMI N, TANAKA H, NISHIMURA O
    水工学論文集 48 2 1519 - 1524 2004年02月 [査読有り][通常論文]
  • 島田 典和, 泉 典洋
    水工学論文集 48 967 - 972 公益社団法人 土木学会 2004年 [査読有り][通常論文]
     
    Steep channels with purely erosional beds are characterized by a series of steps formed on beds. In this paper, experiments were performed in order to study the formation and the evolution of the steps. In the experiments, the wavelength of steps were found to be of the order of ten to sixty times the initial flow depth before the formation of steps. It was observed that the wavelengths reduced over time. In order to investigate the inception of steps, a linear stability analysis is performed with the use of the spectral method with the Chebyshev polynomial. The experimental results were compared with the theoretical results derived from a linear stability analysis. The agreement between theory and experiments were found to be good.
  • ポンプロミン アディチャイ, 泉 典洋, 辻本 哲郎
    応用力学論文集 7 997 - 1004 公益社団法人 土木学会 2004年 [査読有り][通常論文]
     
    The existing linear stability analysis of incipient channelization was limited to the case of self-preserving slope profiles. In this study, the theory is extended to include the channelization on slopes with arbitrary shapes under the assumption that the growth of perturbation is sufficiently faster than the evolution of base state slope profiles; thus, a time derivative term in base state equations is neglected in the linear level (frozen time approach). As the result of a momentary stability analysis, the dominant wavelength is found to decrease with increasing curvature of slopes. In addition, the analysis shows the possibility of channelization even in the case of arbitrary slope profiles.
  • 谷川 麻子, 泉 典洋, 田中 仁
    応用力学論文集 7 1005 - 1012 公益社団法人 土木学会 2004年 [査読有り][通常論文]
     
    Beach cusps are uniformly spaced, arcuate scallops formed at beaches. They are inseparably connected with nearshore currents. The nearshore current system forms a variety of circulation patterns, which have been attracting many researchers' interest since long time ago. While several theories have been proposed on the formation of nearshore current systems, Hino attributed their formation to the dynamic instability, and explained it in terms of linear stability analysis. In this study, his theory is revisited and improved in several aspects.
  • 五十嵐 章, 泉 典洋, 細田 尚
    水工学論文集 48 493 - 498 公益社団法人 土木学会 2004年 [査読有り][通常論文]
     
    Uniform flow on a relatively steep channel is known to be unstable to evolve into a wave train, which is termed roll waves. Though roll waves have long been studied, their wavelength cannot be theoretically determined. In this study, a linear stability analysis on the wavelength of fully-developed roll waves is performed. It is found that the instability of the fully-developed roll waves is maximized when the wavelength is 0.1-1, and roll waves with infinitely long or infinitesimally short wavelengths are neutrally stable. In order to study the development of roll waves and to verify the theory, numerical simulation is performed. As the distance from the inlet increase, roll waves tend to increase in the wavelength, and to approach a constant wavelength asymptotically.
  • PILAILAR S, SAKAMAKI T, IZUMI N, TANAKA H, NISHIMURA O
    水工学論文集 47 1033 - 1038 2003年02月 [査読無し][通常論文]
  • PORNPROMMIN A, IZUMI N, TSUJIMOTO T
    水工学論文集 47 697 - 702 2003年02月 [査読有り][通常論文]
  • 泉 典洋, 田中 仁, 坪井 宏介, 伊達 政直
    土木学会論文集 2003 740 109 - 120 公益社団法人 土木学会 2003年 [査読有り][通常論文]
     
    河川流が卓越する河口部を対象に模型実験を行い, 河口噴流における流速および浮遊砂濃度の分布構造, 掃流砂および浮遊砂による河口テラスの初期形成機構を明らかにした. また著者らの一部が提案した理論の妥当性を検証した結果, 理論と実験結果には良好な一致が認められ, 浮遊砂が支配的な場合, 噴流軸の両側に堆積が生じることが実験によっても示された. さらに河口テラスからデルタへの発達過程に関する実験を行い, 浮遊砂が支配的な場合, 掃流砂が支配的な場合とは明らかに異なる, 鳥趾状デルタに近い堆積形状へと発達することが示された.
  • 泉 典洋, 田中 仁, 伊達 政直
    土木学会論文集 2003 740 95 - 107 公益社団法人 土木学会 2003年 [査読有り][通常論文]
     
    河川流が卓越する河口部を対象にして, 河口噴流の流速分布とそれによって形成される河口テラスの初期堆積形状を予測する数学モデルを提案した. 横断方向の流速分布および浮遊砂濃度の相似性を仮定し, 流れの運動方程式および浮遊砂の移流分散方程式を横断方向に積分することによって得られる簡便な常微分方程式を解くことによって流速分布および浮遊砂濃度分布を求めている. さらに流速および浮遊砂濃度分布から掃流砂および浮遊砂によって形成される河口テラスの初期堆積形状を求めた. 解析の結果, 掃流砂が支配的であるとき, 噴流の流軸上に堆積そしてその両側に侵食が生じ, 浮遊砂が支配的で移流拡散の影響が比較的小さいとき, 流軸上に侵食そしてその両側に堆積が生じることが明らかとなった.
  • 山口 里実, 泉 典洋
    土木学会論文集 2003 740 75 - 94 公益社団法人 土木学会 2003年 [査読有り][通常論文]
     
    洪水時, 流量の比較的小さい領域で発生した河床波は, 流量増加に伴って消滅し, 流量減少時に再び発生することが知られている. また河床波から平坦床へ遷移する際の流量が, 平坦床から河床波に遷移する際の流量と異なるというヒステリシス現象が見られることが知られている. 本研究は, 弱非線形解析の手法を用いて, ヒステリシス現象の原因の一つが, 平坦床から河床波に遷移する際に見られる亜臨界分岐であることを理論的に示したものである.
  • 山口 里実, 泉 典洋, 五十嵐 章
    水工学論文集 47 613 - 618 公益社団法人 土木学会 2003年 [査読有り][通常論文]
     
    The transition process of dune formation is known to be characterized by the hysteresis that the critical Froude number for dunes to disappear with increasing discharge is larger than that to reappear with decreasing discharge. In this study, the experiments on the transition process of dune formation were performed with an experimental flume. After the discharge was gradually increased until dunes disappear, it was gradually decreased until the dunes reappear. The hysteresis was observed in the transition process of dune formation. The results of the experiments are found to be reasonably well explained by the weakly nonlinear stability analysis of dune formation performed by the first and second authors.
  • 谷川 麻子, 泉 典洋, 田中 仁
    水工学論文集 47 607 - 612 公益社団法人 土木学会 2003年 [査読有り][通常論文]
     
    In the alluvial reach of the Natori river, two distinctive morphological features can be seen. The reach from the upstream of Taihaku bridge to the confluence with the Hirose river is characterized by unstable, braided configuration while the reach downstream of the confluence is rather stable. This study provides a theoretical explanation for the distinctions between two reaches in a same river by the use of the theories of stable channel cross-section of straight gravel and sand-silt rivers, and the theory of bar formation. The differences of grain size and bed slope are found to cause such a contrast.
  • 泉 典洋, 藤井 健司
    土木学会論文集 2003 747 95 - 109 公益社団法人 土木学会 2003年 [査読有り][通常論文]
     
    粘土などの粘着性の強い土壌で構成された斜面上にはガリが形成され, それによって土壌侵食が促進されることが知られている. また粘着性が比較的弱い火山灰などで構成された斜面上にも同様のガリが形成され, 土砂の流出が急激に進む現象が観察されている. 粘着性が弱い場合, 土砂の侵食抵抗が弱く侵食量が大きくなるため, 流水中における浮遊砂濃度の上昇に伴って堆積が生じはじめる. 本研究では, 粘着性土砂で構成された斜面上における水路群形成の理論を, 堆積が無視できないような粘着性の弱い土砂で構成された斜面上におけるガリ群の形成に拡張したものである. 解析の結果によると, 底面勇断力が大きく十分な巻上げが存在するような場合, フルード限界水深の600-1500倍の間隔でガリ群が形成されることが明らかとなった.
  • 泉 典洋
    応用力学論文集 6 959 - 966 公益社団法人 土木学会 2003年 [査読有り][通常論文]
     
    A mathematical model of the channelization on steep slopes is presented in this study. A linear stability analysis is performed with the use of the shallow water equations and the Exner equation extended for purely erosional beds. The analysis is found to be similar to that for channelization on mild slopes that the author has presented. The characteristic wavelength associated with the maximum growth rate is of the order of ten times the Froude-critical depth divided by the bed resistance coefficient. The resistance coefficient is estimated of the order of 0.01; thus, the dominant channel spacing is of the order of 1000 times the Froude-critical depth.
  • 泉 典洋, PORNPROMMIN Adichai
    土木学会論文集 2002 712 73 - 86 公益社団法人 土木学会 2002年 [査読有り][通常論文]
     
    単列交互砂州の非線形解析手法として従来行われてきた増幅率展開法は, 増幅率を微小パラメータとして展開するため, その適用は最も小さい臨界アスペクト比近傍, すなわち単列交互砂州の近臨界域のみに限られるという欠点があった. 本研究ではこの制限を除くために, 振幅を微小パラメータとして展開する振幅展開法を用い, 単列交互砂州のみならず複列砂州の場合にも適用できる弱非線形解析を提案した. 単列交互砂州および複列砂州の波長および平衡振幅について理論結果と実験結果を比較したところ良好な一致が見られた.
  • 泉 典洋
    土木学会論文集 2002 712 45 - 56 公益社団法人 土木学会 2002年 [査読有り][通常論文]
     
    大陸棚周縁部には海底峡谷 (submarine canyon) と呼ばれる峡谷状の地形が見られるが, その成因の一つとして, 大陸棚上を流下する乱泥流 (turbidity current) と呼ばれる密度流が挙げられる. 本論文では乱泥流の運動方程式および連続式, 浮遊粒子の移流方程式, 乱泥流による海底地形変化を記述する方程式を組み合わせ, 線形安定解析の手法を用いることによって, 海底峡谷の初期形成機構について理論的説明を試みた. 理論によれば, 峡谷群の初期形成間隔は乱泥流の層厚のおおよそ1500倍~8000倍となることが明らかとなった. 乱泥流の層厚が10cm~1mのオーダーであるとすると峡谷群の間隔は150m~8kmとなり, 実際の間隔とも良好に一致する結果が得られた.
  • 井上 かおり, 田中 仁, 泉 典洋
    海岸工学論文集 49 516 - 520 公益社団法人 土木学会 2002年 [査読有り][通常論文]
     
    石巻湾西端の野蒜須崎浜は湾沿岸から運ばれた漂砂や鳴瀬川の供給土砂により明治前後から発達した. 今日, 河川上流の治山・治水が進み, また湾中央ではヘッドランド等海岸構造物が設置され, 野蒜海岸に流入する土砂移動量の変化が予想される. そこで, これまでの野蒜海岸を形成した土砂移動量を調べるため, ヘッドランドを考慮しない1998年以前の長期土砂移動量を評価した. 評価方法として, 空中写真による汀線解析と野蒜海岸の堆積土砂量の概算, 河床変動計算による鳴瀬川供給土砂量の計算, 湾西側の沿岸漂砂量の計算を行った. その結果, 河川・海岸を含め野蒜沿岸の長期土砂移動量は10<SUP>4</SUP>-10<SUP>5</SUP>m<SUP>3</SUP>/sであることが示された.
  • 泉 典洋, Vithana H. P. V, 田中 仁
    水工学論文集 46 773 - 778 公益社団法人 土木学会 2002年 [査読有り][通常論文]
     
    It is commonly observed that, in pocket beaches, river mouths are located at either end of beaches adjacent to one of the headlands. Izumi <I>et. al.</I> presented a linear stability theory to explain the instability of river mouths in pocket beaches. The theory shows that river mouths cannot stay stably in the central region of beaches but can stay only within regions near either end of beaches when the capability of longshore sediment transport is not sufficient compared with the load of river sediment supply. In this study, a series of experiments are performed to study the instability of river mouths with the use of a simplified physical model. It is found that river mouths are always unstable at the center of beaches even without the shielding effect of headlands on the wave energy; thus, the shielding effect is not essential for the instability. Contrary to the theoretical results, river mouths are unstable at the beach center even if sediment supply is not sufficiently large.
  • 山口 里実, 泉 典洋
    水工学論文集 46 707 - 712 公益社団法人 土木学会 2002年 [査読有り][通常論文]
     
    On the transition process of dune formation, it is known that a hysteresis is observed that the critical Froude number at which dunes disappear when discharge increases is larger than the critical Froude number at which dunes reappear when discharge decreases. In this study, in order to explain the hysteresis observed in the dune transition, a weakly nonlinear analysis is performed with the use of the growth rate expansion method. The analysis leads a nonlinear amplitude equation, which shows that when wavenumber is 0.1-0.4, the type of bifurcation appeared in the dune transition is subcritical for &sigma;=0.8. This result implies that there is a possibility that the hysteresis is caused by the subcritical bifurcation.
  • 山口 里実, 泉典 洋
    応用力学論文集 5 639 - 648 公益社団法人 土木学会 2002年 [査読有り][通常論文]
     
    It has been known that a series of steps often develop on an erosional bed. In this study, a weakly nonlinear stability analsys is perfomed with the use of the two-dimensional Reynolds equations. The anlysis leads the value of the first Landau coefficient in a nonlinear amplitude equation with the use of the amplitude expansion method. The results show that when the wavenumber is larger than the chracteristic wavenumber obtained in the linear stability analysis, the perturbation keeps growing in the process of the nonlinear development_ This result corresponds to the fact that steps on erosional beds develop to form a series of waterfall-like steps or overhanging cliffs in channels. This does not mean the steps can actually grow infinitely. Fully-developed steps, which cannot be described by this formulation, can be illustrated by Parker et al's theory to have an equilibrium amplitude.
  • ポンプロミン アディチャイ, 寺本 敦子, 泉典 洋, 北村 忠紀, 辻本 哲郎
    応用力学論文集 5 629 - 638 公益社団法人 土木学会 2002年 [査読有り][通常論文]
     
    Numerical simulations are performed to investigate the characteristics of the formation of alternate and multiple bars with the use of the NHSED2D model. The results of the simulations show reasonably good agreement with the results of the theoretical analysis and the experiments. It is found that periodic boundary conditions with an insufficiently small calculation domain tend to stabilize multiple bars. It is also found that there is possibility that different initial configurations lead to different equilibrium states. The reduction of the bar mode can be well explained by the theoretical results that the difference between the dominant modes associated with the maximum growth rate and the maximum equilibrium amplitude. The irregularity appeared in the reduction process of the bar mode is suggested to be caused by the nonlinear interaction between multiple modes of bars.
  • 泉 典洋, Huy Phuong Nguyen
    応用力学論文集 4 611 - 618 土木学会 2001年 [査読有り][通常論文]
  • 山口 里実, 泉 典洋
    水工学論文集 45 751 - 756 公益社団法人 土木学会 2001年 [査読有り][通常論文]
     
    The bed form of steep channels are often characterized by a series of steps. In this paper, in order to investigate the mechanism of the inception of steps, a linear stability analysis is performed with the use of the two-dimensional Reynolds equations and the Exner equation for bed erosion. The analysis reveals that the flat bed becomes unstable resulting in the growth of sinusoidal perturbations when the Froude number is larger than 0.6-0.9 and the wavenumber is smaller than 0.7-1.0. The characteristic wavenumber of inceptive steps are in the order of 0.1-1, corresponding to a wavelength of 6-60 times the flow depth. The comparison between the predicted wavenumbers in this analysis and the measurements in Sawai's experiments shows a reasonably good agreement. The analysis can also explain that the steps migrate upstream, which agrees with the observational results.
  • 泉 典洋, 首藤 伸夫, 田中 仁, VITHANA H.P
    応用力学論文集 4 581 - 590 公益社団法人 土木学会 2001年 [査読有り][通常論文]
     
    A commonly observed feature of pocket beaches confined by two rocky headlands is that river mouths are located at either end of beaches adjacent to one of headlands. This study presents a theoretical model of instability of river mouth locations in pocket beaches in terms of a linear stablity analysis. The theory shows that river mouths cannot exist stably around the central region of beaches and only can be located at either end of beaches when the load of river sediment supply relative to the dimensions of rivers are comparatively larger than the capability of longshore sediment transport relative to the dimensions of beaches.
  • 本堂 亮, 泉 典洋, 田中 仁
    海岸工学論文集 47 1 536 - 540 公益社団法人 土木学会 2000年10月 [査読有り][通常論文]
  • G Parker, N Izumi
    JOURNAL OF FLUID MECHANICS 419 203 - 238 2000年09月 [査読有り][通常論文]
     
    An erodible surface exposed to supercritical flow often devolves into a series of steps that migrate slowly upstream. Each step delineates a headcut with an associated hydraulic jump. These steps can form in a bed of cohesive material which, once eroded, is carried downstream as washload without redeposition. Here the case of purely erosional, one-dimensional periodic, or cyclic steps in cohesive material is considered. The St. Venant shallow-water equations combined with a formulation for sediment erosion are used to construct a complete theory of the erosional case. The solution allows wavelength, wave height, migration speed and bed and water surface profiles to be determined as functions of imposed parameters. The analysis also admits a solution for a solitary step, or single headcut of self-preserving form.
  • N Izumi, G Parker
    JOURNAL OF FLUID MECHANICS 419 239 - 262 2000年09月 [査読有り][通常論文]
     
    A linear stability analysis of incipient channellization on hillslopes is performed using the shallow-water equations and a description of the erosion of a cohesive bed. The base state consists of a laterally uniform Froude-subcritical sheet flow down a smooth, downward-concave hillslope profile. The downstream boundary condition consists of the imposition of a Froude number of unity. The process of channellization is thus driven from the downstream end, The flow and bed profiles describe a base state that migrates at constant, slow speed in the upstream direction due to bed erosion. Transverse perturbations corresponding to a succession of parallel incipient channels are introduced. It is found that these perturbations grow in time, so describing incipient channellization, only when the characteristic spacing between incipient channels is on the order of 6-100 times the Froude-critical depth divided by the resistance coefficient. The characteristic wavelength associated with maximum perturbation growth rate is found to scale as 10 times the Froude-critical depth divided by the resistance coefficient. Evaluating the friction coefficient as on the order of 0.01, an estimate of incipient channel spacing on the order of 1000 times the Froude-critical depth is obtained, The analysis reveals that downstream-driven channellization becomes more difficult as (a) the critical shear stress required to erode the bed becomes so large that it approaches the Froude-critical shear stress reached at the downstream boundary and (b) the Froude number of the subcritical equilibrium how attained far upstream approaches unity. Alternative mechanisms must be invoked to explain channellization on slopes high enough to maintain Froude-supercritical sheet flow.
  • 泉典洋, 松田幸子, 田中仁
    水工学論文集 44 419 - 424 2000年02月 [査読有り][通常論文]
  • 山口里実, 泉典洋
    水工学論文集 43 605 - 610 1999年02月 [査読有り][通常論文]
  • 泉 典洋
    土木学会論文集 = Proceedings of JSCE 614 65 - 75 公益社団法人 土木学会 1999年02月 [査読有り][通常論文]
     
    本研究では, 斜面下流端から発生し上流側へ発達していく水路群形成過程を対象に, 表面流を表現する浅水流方程式とそれによる侵食の式を用いて線形安定解析を行うことによって, 水路群の形成される初期間隔を予測する理論を提案した. 理論によると波長が限界水深/抵抗係数の6倍~100倍程度の範囲でのみ擾乱は発達し得ることが明らかとなった. また擾乱の発達率を最大とする卓越波長は限界水深/抵抗係数の10倍程度となることが明らかとなった. 抵抗係数が0.01のオーダーであることから, 水路群の形成間隔は限界水深の1000倍程度になることが結論される. また斜面勾配あるいは限界剪断力が相対的に大きくなると水路化は起きにくくなることが示された.
  • N Izumi, N Shuto, H Tanaka
    COASTAL SEDIMENTS '99, VOLS 1-3 628 - 643 1999年 [査読有り][通常論文]
     
    A commonly observed feature of pocket beaches confined by two rocky headlands is that river mouths are located at either end of beaches adjacent to one of headlands. This study presents theoretical models of instability of river mouth locations in pocket beaches. The theory shows that river mouths cannot exist stably in the central region of beaches but can exist only within regions near the both ends of beaches when the capability of longshore sediment transport relative to the dimensions of beaches is not sufficiently large in comparison with the load of river sediment supply relative to the dimensions of rivers.
  • Inceptive topography of fluvial-dominated river mouth bars
    N Izumi, H Tanaka, M Date
    RIVER SEDIMENTATION: THEORY AND APPLICATIONS 899 - 904 1999年 [査読有り][通常論文]
     
    Inceptive topography of fluvial-dominated river mouth bars is studied theoretically with the use of simple mathmatical models of tidal jets and sediment deposition. The theory shows that deposition occurs on the jet axis and a middle ground bar is formed when bedload is dominant and that deposition occurs on both sides of the jet axis and subaquious natural levees are formed when suspended load is dominant. It is suggested that the fiver mouth bars with dominant bedload develop into fan deltas, and the bars with dominant suspended load into elongate deltas.
  • 泉典洋, 山口里実
    水工学論文集 42 1105 - 1110 1998年02月 [査読有り][通常論文]
  • 伊達政直, 泉典洋, 田中仁
    水工学論文集 42 1129 - 1134 1998年02月 [査読有り][通常論文]
  • 泉典洋, 山口里実
    水工学論文集 41 871 - 876 1997年02月 [査読有り][通常論文]
  • 泉 典洋, Parker Gary
    土木学会論文集 1997 565 43 - 55 公益社団法人 土木学会 1997年 [査読有り][通常論文]
     
    自然河川によく見られる, 河床が礫, 河岸が細砂で構成される河道地形の形成メカニズムを説明するための数学モデルを提案した. 砂床河川の平衡横断面形状の理論を, アクティブレイヤーにおける細砂の体積存在率<i>p</i>を導入することによって, 一部礫相が露出している場合に拡張した. 礫床における解と細砂に覆われた河岸部における解を接続することによって細砂の堆積位置とその形状を理論的に求めた. 理論によれば, 中央水深及び河床勾配が十分大きく, 細砂の粒径が十分小さいときは, 浮遊砂は側岸部に堆積することが理論的に示された. また, 中央水深及び勾配が小さく粒径が大きいとき, 浮遊砂は河道中央部に堆積することが明らかとなった.
  • 泉 典洋, 池田 駿介, Parker Gary
    土木学会論文集 1997 565 31 - 41 公益社団法人 土木学会 1997年 [査読有り][通常論文]
     
    直線砂床河川の平衡横断形状の理論を側岸付近に透過水制が存在する場合に拡張することによって, その平衡横断面形状を理論的に求めた. その際, 水制が底面剪断力を減ずる働きを考慮して水制域での解を求め, 非水制域での解と接続することによって平衡状態での横断面形状及び中央水深を導いた. その結果, 平衡状態においては水制域はほぼ完全に砂に埋没してしまうこと, 流量及び河床勾配が変化しないとすると平衡水深は通常の水制密度の範囲内 (χ=1~100) で数%から3, 40%大きくなることが理論的に示された. さらに, 水制設置前後で流量と流砂量が保存されるという平衡縦断形状の考え方を, 本理論とともに (X=10と仮定して) 実際のケースに適用すると, 水制設置後, 平衡水深が70%程度大きくなるという実測結果を説明することが可能となった.
  • 伊達 政直, 泉 典洋, 田中 仁
    海岸工学論文集 44 591 - 595 公益社団法人 土木学会 1997年 [査読有り][通常論文]
  • 泉 典洋, 池田 駿介
    水工学論文集 40 915 - 920 公益社団法人 土木学会 1996年 [査読有り][通常論文]
     
    Self-preserving profiles have been observed in experimentally produced onedimensional deltas. We analytically derive such a self-preserving profile from the St. Venant shallow water equations and the continuity equation of sediment, giving profiles of concave form. The theory predicts that the increasing height of the delta front decelerates the migration of the front and reduces the gradient of the longitudinal profile. The experimental results support these results.
  • 泉 典洋, PARKER Gary
    土木学会論文集 = Proceedings of JSCE 521 79 - 91 公益社団法人 土木学会 1995年08月 [査読有り][通常論文]
     
    斜面下流端のステップ近傍で発生したガリは上流側へ向かって水路へと発達しながら複雑なチャンネルネットワークを形作っていく. 本研究では発生初期のガリの発達メカニズムを調べるために, 下流端にステップが存在する緩やかな一様勾配斜面を考え, そのステップにサイン形状を有する斜面方向の微小擾乱を与えたときの斜面上の流速分布及び水面形状を浅水流方程式を特異摂動法を用いて解くことによって求めた. それによると擾乱の影響が顕著な下流端近傍の薄い層内では降雨およびレイノルズ応力の影響は無視できることがわかった. また計算によって, 上流方向にくぼんだ部分に流れが集中する様子を再現でき, それらの結果に限界掃流力を用いた水路の初期形成仮説を適用した結果, (水深/斜面勾配) 程度のオーダーの卓越波長が得られた.
  • 泉 典洋, パーカー ゲーリー
    水工学論文集 39 665 - 670 公益社団法人 土木学会 1995年 [査読有り][通常論文]
     
    In natural rivers, it is commonly seen that gravel beds are delineated by sandy banks. A theoretical model to explain the &ldquo;gravel bed sand bank morphology&rdquo; of straight rivers is presented in this study. The theory of stable cross-section of gravel rivers is combined with that of sand-silt rivers by introducing the concept of an available function (<I>P</I>) of fine sands on gravel beds. The theory predicts the location of sand deposit in the channel for given center depth, slope and center value of <I>P</I> (available function).
  • N IZUMI, G PARKER
    JOURNAL OF FLUID MECHANICS 283 341 - 363 1995年01月 [査読有り][通常論文]
     
    The ubiquitous presence of river drainage basins in the terrestrial environment suggests that distributed overland flow generated by rainfall tends to spontaneously organize itself into dendritic systems of discrete channels. Several recent numerical models describe the evolution of complete drainage basins from the initial condition of rainfall on a flat, tilted plateau, the surface of which has been provided with random elevation perturbations. These analyses model overland flow via the assumption of a perfect balance between gravitational and frictional terms, i.e. in terms of normal flow. Linear stability analysis applied to the normal flow model has been shown, however, to fail to select a wavelength corresponding to a finite distance of separation between incipient basins. This suggests that the normal flow model may not be a sufficient basis for studying drainage basin development, especially at the finest scales of morphologic significance. Here the concept of a threshold condition for bed erosion is combined with an analysis of the full equations of shallow overland how in order to study wavelength selection. Classical linear stability analysis is shown to be inadequate to analyse the problem at the level of inception. An alternative linear analysis of bed perturbations based on the threshold condition is developed, and shown to lead to the selection of finite wavelength of the correct order of magnitude. The analysis here is driven from the upstream direction in that bed erosion is first caused only when sufficient flow has gathered from upstream due to rainfall. A downstream-driven theory of incipient channelization that is not necessarily dependent upon rainfall is presented in Izumi (1993), and is presently in preparation for publication.
  • 泉 典洋, パーカー ゲーリー
    水工学論文集 38 203 - 208 公益社団法人 土木学会 1994年 [査読有り][通常論文]
     
    The process of channel inception is studied theoretically. Instead of the normal flow assumption used by Smith and Britherton, St. Venant shallow water equations are adopted as a flow model to include the effect of backwater and the Reynolds stress. Velocity and depth profiles of a sheet flow on a perturbed plateau is analytically solved using a perturbation technique. It is found that the flow is gathered in troughs on the plateau and that the flow intensification is maximized when perturbation wavelength is of the order of the flow depth devided by the slope.
  • EFFECTS OF PILE DIKES ON FLOW RETARDATION AND SEDIMENT TRANSPORT
    S IKEDA, N IZUMI, R ITO
    JOURNAL OF HYDRAULIC ENGINEERING-ASCE 117 11 1459 - 1478 1991年11月 [査読有り][通常論文]
     
    A mathematical model for defining lateral distributions of fluid velocity and suspended sediment concentration in straight channels with pile dikes near the banks is presented. Singular perturbation and matched asymptotic expansion techniques are employed to derive the distributions. It is found that suspended sediment is transported toward the pile dike region due to lateral turbulent diffusion, the amount of which is predicted by the theory. Laboratory work has revealed that the lateral diffusivities of fluid momentum and suspended sediment are identical with those observed for flows without pile dikes. The vertical diffusivity of suspended sediment is found not to be affected by pile dikes. The laboratory tests support the present model.
  • STABLE CHANNEL CROSS-SECTIONS OF STRAIGHT SAND RIVERS
    S IKEDA, N IZUMI
    WATER RESOURCES RESEARCH 27 9 2429 - 2438 1991年09月 [査読有り][通常論文]
     
    A mathematical model is presented for defining the size and cross section of self-formed straight sand rivers in which sediments are actively transported everywhere as bedload and suspended load. A balance of lateral bedload and lateral diffusive transport of suspended sediment is imposed to maintain a stable channel cross section. Singular perturbation technique is employed to solve the sediment balance equation, from which a relation for stable depth is derived. A resistance formula for dune-covered beds is used to obtain stable width. It is revealed theoretically that the channel center depth relative to sediment size is approximately proportional to S-0.8 for natural sand rivers, in which S is longitudinal slope. The analysis is found to agree reasonably well with available laboratory and field data.
  • 泉 典洋, 池田 駿介
    土木学会論文集 429 p57 - 66 土木学会 1991年05月 [査読有り][通常論文]
  • 泉 典洋, 池田 駿介
    土木学会論文集 1991 429 57 - 66 公益社団法人 土木学会 1991年 [査読有り][通常論文]
     
    直線砂床河川では浮遊砂と掃流砂の横断方向輸送の釣り合いにより河道が維持されている. 本論文では厳密にこの現象を定式化し, 安定形状, 水深および河幅を求めた. その結果, その形状は流量, 粒径, 勾配の関数として表わされることが判明した. 特に水深は勾配の約-0.8乗に比例することを明らかにし, 又, 従来予測されていなかった河幅にっいても理論式を提案し, これらは測定値を適切に説明するものであった.
  • 池田 駿介, 泉 典洋
    土木学会論文集 1991 434 47 - 55 公益社団法人 土木学会 1991年 [査読有り][通常論文]
     
    樹木や杭が片岸側にある場合について, 水深平均流速分布ならびに浮遊砂濃度分布に関する理論解析を行い, 横断方向拡散係数を求める方法を示した. この方法に従い, 幅1mの水路を用いて拡散係数を測定した. さらに, 河岸のような側斜面の場合についても同様な解析を行い, 幅50cmの水路を用いて拡散係数を求めた. 以上の結果, いずれの場合も鉛直方向の拡散係数は0.08<i>u</i><sub>*</sub><i>D</i>程度であり, 横断方向拡散係数は0.23<i>u</i><sub>*</sub><i>D</i>程度となることを示した.
  • TRANSVERSE DIFFUSION RATES OF FLUID MOMENTUM AND SUSPENDED SEDIMENT NEAR SIDE BANKS
    S IKEDA, N IZUMI
    ENVIRONMENTAL HYDRAULICS, VOLS 1 AND 2 403 - 408 1991年 [査読有り][通常論文]
  • WIDTH AND DEPTH OF SELF-FORMED STRAIGHT GRAVEL RIVERS WITH BANK VEGETATION
    S IKEDA, N IZUMI
    WATER RESOURCES RESEARCH 26 10 2353 - 2364 1990年10月 [査読有り][通常論文]
  • 泉 典洋, 池田 駿介
    土木学会論文集 1989 411 151 - 160 公益社団法人 土木学会 1989年 [査読有り][通常論文]
     
    Effect of bank vegetation on the stable channel cross-section of straight gravel rivers is studied theoretically, in which singular perturbation and matched asymptotic expansion techniques are employed to derive the lateral distributions of depth-averaged fluid velocity and the bed shear stress. A condition of sediment incipient motion is imposed at the junction of the bed and the banks to derive the stable depth, and a formula for resistance to flow is used to obtain the stable width. It is revealed that a thicker vegetation yields a larger depth and a smaller width. Increasing discharge is found to increase the effect of vegetation. The analysis is found to agree reasonably well with available field data.
  • 泉 典洋, 池田 駿介, 伊藤 力生
    水理講演会論文集 33 313 - 318 公益社団法人 土木学会 1989年 [査読有り][通常論文]
     
    Mathmatical models for defining the lateral distributions of velocity and suspended sediment concentration in channels with vegetation are presented. Singular perturbation technique is used to define the velocity distribution, from which the sediment distribution is derived. Measurements of the velocity and the sediment concentration in a laboratory flume with vegetation models are made. These data support the model presented herein, and it is revealed that the lateral momentum and the mass diffusivity are larger than those for open channel flow without vegetation. It is found that the vertical diffusivity is not governed by the local friction velocity. The transportation of suspended sediment due to vegetation is thus quantified.
  • 小池 俊雄, 玉井 信行, 高橋 裕, 泉 典洋, 岡村 次郎
    土木計画学研究・論文集 6 105 - 112 公益社団法人 土木学会 1988年 [査読有り][通常論文]
     
    The structure of evaluation of a river space in a city is studied at the Kanda river and the Syakujii river which are typically urbanized in Tokyo. The river space is devided into the physical space and the psychological space. The influence of the geometrical characteristics of the upper- and mid- Kanda river on evaluation of the physical river space is examined. A preferable structure of river space is gained by the psychophysical approach. The cognitive model for evaluation of the psychological river space is presented. The difference of the structures of evaluation is examined at two zones in the Syakujii river using the model.

講演・口頭発表等

  • 藤田和典, 森勇, 横川美和, FERNANDEZ Roberto, CZAPIGA Matt, BERENS John, KWANG Jeffrey, 内藤健介, PARKER Gary, 泉典洋, 成瀬元
    日本堆積学会大会プログラム・講演要旨 2018年03月
  • FUJITA Kazunori, MORI Isamu, YOKOKAWA Miwa, FERNANDEZ Roberto, CZAPIGA Matt, BERENS John, KWANG Jeffrey, NAITO Kensuke, PARKER Gary, IZUMI Norihiro, NARUSE Hajime
    日本地球惑星科学連合大会予稿集(Web) 2018年
  • 西村柾哉, 前田健一, 櫛山総平, 高辻理人, 泉典洋, 古溝幸永
    地盤工学研究発表会発表講演集(CD-ROM) 2018年
  • 開坂亮太, 泉典洋
    土木学会北海道支部論文報告集(CD-ROM) 2018年01月
  • 渋谷幸子, 泉典洋, 山田朋人
    土木学会北海道支部論文報告集(CD-ROM) 2018年01月
  • 恒川和久, DE LIMA Adriano Continho, 泉典洋
    土木学会北海道支部論文報告集(CD-ROM) 2018年01月
  • 小林素直, 田口真矢, LIMA Adriano C, 泉典洋
    土木学会北海道支部論文報告集(CD-ROM) 2018年01月
  • 久原愛加, DE LIMA Adriano Coutinho, 泉典洋
    土木学会北海道支部論文報告集(CD-ROM) 2018年01月
  • 谷川徹, DE LIMA Adriano Coutinho, 泉典洋
    土木学会北海道支部論文報告集(CD-ROM) 2018年01月
  • 波状道路の形成理論  [通常講演]
    瀧上直斗, 泉典洋
    土木学会北海道支部論文報告集(CD-ROM) 2018年01月
  • 西村 柾哉, 前田 健一, 櫛山 総平, 泉 典洋, 齊藤 啓
    計算工学講演会論文集 Proceedings of the Conference on Computational Engineering and Science 2017年05月
  • 藤田 和典, 泉 典洋, 成瀬 元, 森 勇, 横川 美和, Roberto Fernandez Arrieta, Matt Czapiga, John Berens, Jeffrey Kwang, 内藤 健介, Gary Parker
    日本地質学会学術大会講演要旨 2017年 
    台風18号により学術大会の一部プログラムが中止となりましたが,それに伴い特別セッションが開催され,本発表は特別セッション内で発表が行われました.
  • 横川 美和, 成瀬 元, 武藤 鉄司, 泉 典洋
    日本地質学会学術大会講演要旨 2016年
  • River Flow - Proceedings of the International Conference on Fluvial Hydraulics, RIVER FLOW 2016 2016年01月 
    © 2016 Taylor & Francis Group, London. Based upon the shallow water equations, linear and nonlinear stability analyses are conducted on an open channel viscous flow covered with vegetation on one side. The analyses are applied to a steady turbulent base flow which is characterized by a sub-depth scale turbulence derived from a logarithmic profile of vertical velocity. The linear stability analysis is performed for the cases of temporally growing and spatially growing disturbances. Discrepancies between results from these two approaches are found to be less relevant than those from inviscid analyses. The Landau equation is then derived on the weakly nonlinear basis. The bifurcation pattern is found to be typically supercritical, where the amplitude of the perturbations grows up to an upper bound. Experimental data from previous works support the present theory.
  • 有雅 正修, 山田 朋人, 泉 典洋
    地球環境シンポジウム講演集 2015年09月
  • 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 2015年
  • 横川 美和, 京極 晃年, 小寺 彰, 泉 典洋
    日本地質学会学術大会講演要旨 2015年
  • 一瀬 輪子, 北野 慈和, 山田 朋人, 渡部 靖憲, 泉 典洋
    水文・水資源学会研究発表会要旨集 2015年 
    中緯度地域における総観規模の気象は,偏西風の蛇行及び高低気圧の発生や移動に支配されるが,これは傾圧不安定波として解釈される.傾圧不安定波の室内実験としてはFultzやHideが提唱した回転水槽実験が挙げられる.既往の実験の多くでは,3重の円筒水槽を用い,中心に冷水,外側に温水を入れ,中間に位置する水槽内の流体を作業流体とする.この作業流体は側壁を通して温度差が与えられ,かつ回転させることで傾圧帯の大気の流れの特徴を有することが示されている.これはアニュラス型の実験と呼ばれるが,本実験では,既往の回転水槽実験と異なり,冷源,熱源を水槽の側壁ではなく底面に配置した装置を用いた.アニュラス型の実験では冷熱源としての内壁があるため,蛇行の振幅が一定となっているが,本実験装置には内壁がないため振幅が自由な場合の傾圧不安定波が形成される.さらに極域に相当する水槽中央部の挙動についても解析可能となる. この装置による実験を相互相関法PIV解析及びSR-PIV解析を利用して解析した.以後,地球大気に倣い,半径方向の流速を南北流速,円周方向の流速を東西流速と呼称する.実験条件を,実験開始前の非回転時の水深40mm,水槽の回転数,レーザシート光を挿入する高さ30mmとした.解析の結果,地球上での中緯度地域に当たる帯状領域で水槽の回転と同方向の東西流速が卓越する流れが観測された.この領域は南北方向に蛇行しており,その波数は地球上の偏西風の蛇行と同程度の4から6程度であった.卓越する帯状領域での東西流速の大きさは1分間の平均値にして0.1-0.4mm/sで時間経過によって増減し,負になる場合も存在した.また,東西風速が卓越する帯状領域において,東西方向に交互に正負の渦度が配置することが観測された.これは地球大気における対流圏上層の低気圧,高気圧の配置と類似している.水槽の中心付近の空間平均渦度と卓越する帯状領域の東西流速の時間変化は類似しており,おおむね同期して増減する.この現象と地球大気における極域の現象との比較は,今後の課題としていきたい.
  • 6th Japan-China Geotechnical Symposium, SJGS 2015 2015年01月 
    Mechanical stability of embankments such as road embankments and river dykes is significantly influenced by their internal hydraulic states, as represented by phreatic surface location and pore water pressure distribution. The mass transfer across the embankment surfaces through water infiltration and evapotranspiration, and the internal migration of pore water to/from foundation soil layers are considered to play a major role in dictating the evolution of the hydraulic state. This paper reports a case study in which hydraulic state variations in an embankment in Hokkaido were monitored over 9 months, including a winter period with ground surface freezing and a significant snow cover. The studied embankment was relatively new, constructed with artificially mixed clay and sand which were generated by nearby excavation. The monitoring records indicate a consistent trend of under-drainage to the foundation layer all during the 9 months, with the pore water pressure at deeper parts registering minimum values during winter and reaching maxima during summer. Explanations for this and other observed features were sought by performing unsteady unsaturated seepage flow analysis with some assumed surface input models. Although the adopted models are fairly crude, the analysis results offer important insights into factors that govern the hydraulic state of low-permeability embankment in snowy cold regions.
  • 横川 美和, 山本 真也, Hughes Clarke John E, 泉 典洋
    日本地質学会学術大会講演要旨 2014年
  • 横川 美和, 小寺 彰, 京極 晃年, 泉 典洋
    日本地質学会学術大会講演要旨 2013年
  • 北沢 俊幸, 泉 典洋, 亀尾 桂, K, 乗船研究者, 新井 和乃, 成瀬 元, 石丸 卓哉, 横川 美和, 齋藤 有, 松本 弾, 佐藤 智之, 田中 源吾
    日本地質学会学術大会講演要旨 2013年
  • 長原準也, 泉典洋, 藤田正治, 竹林洋史
    土木学会北海道支部論文報告集(CD-ROM) 2012年02月
  • 北野 慈和, 山田 朋人, 泉 典洋
    水文・水資源学会研究発表会要旨集 2012年 
    線状に発達し特定の地域に長時間とどまり雨を降らせることで知られている線状降水帯の物理的なメカニズムは未だに解明されていないことが多く、科学的に興味のつきない現象である。一方で、2004年新潟・福島豪雨や2004年福井豪雨、2010年北海道豪雨など、多くの水災害を引き起こしている線状降水帯の発生・発達過程を調べることは防災という面でも非常に意義のある研究である。本研究では、線状降水帯の水平方向の形状特性について線形安定性理論を用いて解析する。
    線状降水帯は不安定な大気場に積乱雲が形成され、それが擾乱として下流に流されることによって線状に発達していく結果形成されると考えられている。これと水平方向の形成範囲が類似している現象として安定な大気場に地形性の上昇気流が生じ、それが波となって線状に発達していく山岳波が挙げられる。本研究では安定な大気場に形成される山岳波の理論を不安定な大気場に応用することで、線状降水帯の形状特性を考察する。
    本理論では、Boussinesq近似を施したNavier-Stokes式、連続式及び流体塊は移動時に断熱であるという条件式を基礎式としている(この時、降雨の影響及び熱力学的な効果は問題を複雑化させると考えられるため考慮していない)。また、基本場として区分的線形近似を施した不安定な大気境界層を用いる。これらの基礎式及び基本場により密度成層した大気場に生じる波の分散関係式を得ることができる。この分散関係式を用いて、擾乱によって生じる鉛直方向流速の存在範囲を停留位相法により求める。
    以上の議論から、基本場の密度界面に擾乱を与えた場合に、その擾乱がある時間後に広がる範囲を得ることが出来る。この形状は境界層の最大速度と境界層厚さにより定義されるフルード数、及び大気の不安定の度合いに関する無次元数のみにより決定することが分かった。擾乱の水平方向の広がりは、大気が不安定になるほど増加するが、あるピークを境に減少に転じる。これはフルード数の大小で解釈でき、現象が慣性項に支配されているか重力項に支配されているかによって分類することが出来る。
    以上のように、本研究では山岳波の理論を不安定な大気境界層に応用し水平方向に広がる擾乱の発達範囲を調べた。これらの議論は線状降水帯の形状特性を調べる上で重要になると考えられる。
  • Cyclic steps formed in bedrock rivers  [通常講演]
    Proceedings of the 7th IAHR Symposium on River, Coastal and Estuarine Morphodynamics 2011年
  • Turbidity-current-generated cyclic steps in subaqueous environments  [通常講演]
    Proceedings of the 7th IAHR Symposium on River, Coastal and Estuarine Morphodynamics 2011年
  • Scouring of soft rock imitated with mortar by the collision of gravels  [通常講演]
    Proceedings of the 7th IAHR Symposium on River, Coastal and Estuarine Morphodynamics 2011年
  • A Riverbed Evolution Calculation Method That Considers Variation in Riverbed Erosion of Soft Rock  [通常講演]
    Proceedings of the 7th IAHR Symposium on River, Coastal and Estuarine Morphodynamics 2011年
  • Phase diagram for antidunes and cyclic steps based on suspension index, non-dimensional Chezy resistance coefficient and Froude number  [通常講演]
    Proceedings of the 7th IAHR Symposium on River, Coastal and Estuarine Morphodynamics 2011年
  • Observation and linear stability analysis of formation of rhomboid rills  [通常講演]
    Proceedings of the 7th IAHR Symposium on River, Coastal and Estuarine Morphodynamics 2011年
  • Stability analysis of sand bars using amplitude expansion method  [通常講演]
    Proceedings of the 7th IAHR Symposium on River, Coastal and Estuarine Morphodynamics 2011年
  • Experiments on channel head bifurcation by overland flow  [通常講演]
    Proceedings of the 7th IAHR Symposium on River, Coastal and Estuarine Morphodynamics 2011年
  • Experiments on channel inception on mild slopes composed of cohesive soils  [通常講演]
    Proceedings of the 1st EIT International Conference on Water Resources Engineering 2011年
  • 長原準也, WUBNEH Atinkut Mezgebu, 泉典洋
    土木学会北海道支部論文報告集(CD-ROM) 2010年02月
  • 高畑 知明, 泉 典洋
    日本流体力学会年会講演論文集 2010年 
    The effects of river bed aggradation and degradation on bar instability is analytically studied in terms of linear stability analysis. Weakly non-equilibrium processes are taken into account by the use of the WKBJ method. In the analysis, aggradation or degradation is assumed to be sufficiently slow compared with the bed evolution due to instability, and its non-dimensional speed is used as a small parameter. It is found that river beds become stable and sand bars tend not to be formed under degradation, and that river beds become unstable under aggradation.
  • Wubneh Atinkut Mezgebu, 泉 典洋
    日本流体力学会年会講演論文集 2010年
  • de Lima Adriano Coutinho, 泉 典洋
    日本流体力学会年会講演論文集 2010年
  • 高橋 憂紀, 山村 浩人, 横川 美和, 泉 典洋
    日本流体力学会年会講演論文集 2010年 
    It is suggested by the weakly nonlinear stability analysis that the bifurcation pattern of the flat bed and antidune transition correlates to the stability of upstream-migrating antidunes. In this study, we performed a series of flume experiments to observe the behavior of upstream-migrating antidunes and obtained parameters which characterize the bifurcation patterns. As a result, the strong instability of antidunes was observed when the velocity coefficient exceeds 16, which can be correlated to the subcritical bifurcation. When the velocity coefficient is small, such as around 11, antidunes are stable, showing that it is under the condition of the supercritical bifurcation. These experimental results show that the stability of the upstream-migrating antidunes changes associated with the velocity coefficient.
  • 竹井 義博, 泉 典洋, ポンプロミン アディチャイ
    理論応用力学講演会 講演論文集 2009年06月 
    本研究は比較的研究成果の少ない湧水侵食によるガリ形成のメカニズムを実験を通して調べたものである.実験では湧水侵食が発達しやすいとされる水はけの良い傾斜地を想定し,水路幅150_cm_,水路長120_cm_,水路高17.5_cm_の可変勾配式水路に3号珪砂を用いて作成した浸透層に水を流すことで湧水侵食を発生させ,ガリが形成される様子を観察してゆく.その際,浸透層の層高・斜面勾配・流量を変更することで発達するガリへの影響を規模・形状・形成間隔・進行速度の各項目に着目して解析してゆく.本実験から,斜面勾配の増加に伴いガリの規模の拡大,ガリの分岐発生率の減少や侵食進行速度の増加という傾向が見られた.また,ガリの形成間隔は層高の違いにより斜面勾配の増加に伴い拡大する場合と縮小する場合の2パターン見られた.
  • The formation of dunes in closed conduits  [通常講演]
    Proceedings of the 6th IAHR Symposium on River, Coastal and Estuarine Morphodynamcis 2009年
  • The formation of small-scale fluvial bedforms with active suspended sediment transport  [通常講演]
    Proceedings of the 6th IAHR Symposium on River, Coastal and Estuarine Morphodynamcis 2009年
  • Linear stability analysis of channelization by seepage erosion  [通常講演]
    Proceedings of the 6th IAHR Symposium on River, Coastal and Estuarine Morphodynamcis 2009年
  • 高畑 知明, 泉 典洋
    理論応用力学講演会 講演論文集 2009年 
    流量、川幅、河床材料の粒径の他に上流からの土砂供給量によって、流路形態が決定する。網状流路は川幅水深比が大きく、土砂供給量が多い河川に見られるが、土砂供給が少なくなったときどのような応答をするのかはよく分かっていない。そこで今回は、直線水路を用いて流量、水路幅、河床材料が一定の元、給砂量の違う3パターンの実験を行い、土砂供給の違いが網状流路の流路形態に及ぼす影響を明らかにした。 給砂量の少ない2つの場合は早くから上流端付近で流路幅が狭くなったが、給砂量が最も多い場合は水路幅全体に流れている時間が長かった。また、実験終了時では給砂量が最も多い場合が給砂量の少ない2つの場合より上流から流路が分岐していた。
  • 平塚 智史, 関 陽平, 泉 典洋
    理論応用力学講演会 講演論文集 2009年 
    本研究は研究成果の少ない管路内における河床変動研究の一環として管路内におけるデューンの形成条件についてを実験的に調べたものである。
    実験には奥行80mm、高さ150mm、全長2mの管路を用い、砂を水と共に循環させることで、給砂および給水を使わずに連続して河床変動を観察できる装置を使用した。
    本研究は著者の研究室に所属していた修士、関陽平によって行なわれた管路内におけるデューンの線形安定解析を元にして行なわれており、そこでデューン形成の支配パラメータとして考えられたオイラー数、シールズ数によって実験結果を整理し、考察をすすめた。
    結果、線形安定解析による理論曲線と類似した曲線によってデューンの発生限界をオイラー数、シールズ数で示しうることが分かった。
  • A simple mathematical model of channel bifurcation  [通常講演]
    Mizushima H, Izumi N, Parker G
    RIVER, COASTAL AND ESTUARINE MORPHODYNAMICS: RCEM 2007, VOLS 1 AND 2 2008年
  • The formation of submarine gullies on continental shelves with arbitrary shapes by turbidity currents  [通常講演]
    Yamaguchi K, Izumi N
    RIVER, COASTAL AND ESTUARINE MORPHODYNAMICS: RCEM 2007, VOLS 1 AND 2 2008年
  • Linear stability analysis of fluvial dunes and antidunes incorporating nonequilibrium bedload transport  [通常講演]
    Sato H, Izumi N
    RIVER, COASTAL AND ESTUARINE MORPHODYNAMICS: RCEM 2007, VOLS 1 AND 2 2008年
  • Weakly nonlinear analysis of the dune-flat bed transition with the mixing length turbulent model  [通常講演]
    Izumi N
    RIVER, COASTAL AND ESTUARINE MORPHODYNAMICS: RCEM 2007, VOLS 1 AND 2 2008年
  • Gully development by groundwater seepage  [通常講演]
    Proceedings of Extended Abstracts and Full Papers of the 8th International Conference on Hydro-Science and Engineering 2008年
  • Experiments on the entrainment of sediment by turbidity currents with the use of submarine sediment  [通常講演]
    Proceedings of Extended Abstracts and Full Papers of the 8th International Conference on Hydro-Science and Engineering 2008年
  • Linear stability analysis between river flow and seepage flow  [通常講演]
    Proceedings of Extended Abstracts and Full Papers of the 8th International Conference on Hydro-Science and Engineering 2008年
  • 泉 典洋, 佐藤 博重
    日本流体力学会年会講演論文集 2008年 
    A flat bed becomes unstable and is covered with lower-regime, small-scale bed forms (dunes) when the Froude number is sufficiently small during floods. It is known that either of dune and flat beds can appear in the range of relatively large Froude numbers. This can be attributed by the fact that the the dune-flat bed transition is characterized by subcritical bifurcation. In this paper, a weakly nonlinear stability analysis is performed to show the bifurcation pattern at the dune and flat bed transition is subcritical with the use of a new sediment transport formula incorporating the effect of flow separation.
  • 関 陽平, 泉 典洋
    日本流体力学会年会講演論文集 2008年 
    Interfacial waves between sediment and water in open channels, which are called dunes or antidunes, are formed in the range of small and large Froude numbers. Moreover, a phase lag between Interfacial waves and the free water surface is of importance to the instability. However, instability of the interface without free water surface has not been well understood. In this study, we perform a linear stability analysis of the interface between sediment and water in pipes with the use of the mixing length turbulent model. The analysis results show that the governing parameter is the Euler number and Shields parameter, and that the interface is unstable in the range of relatively small Euler numbers.
  • 中里 遥介, 泉 典洋
    日本流体力学会年会講演論文集 2008年 
    A flat bed becomes unstable, and is covered with small-scale bed waves during floods. One of the purposes of this study is to extend existing linear stability analysis taking into account only bedload to the case with active suspended sediment transport. It is found from the analysis that, with increasing suspended sediment, the critical Froude number for the bed instability is reduced, and the formation of small-scale bed waves tends to be inhibited.
  • 関 陽平, 泉 典洋
    理論応用力学講演会 講演論文集 2008年 
    矩形管路内のデューンの発生条件を線形安定解析により求めた.今回は泉が行った方法に倣った.その方法は,Navier-Stokes方程式に混合距離モデルとChebyshev多項式を用いたスペクトル法を用い流関数を求め,これとexner方程式から発生条件を得るものである.その結果を波数とフルード数を両軸とするコンタ図にした.結果は不安定となりデューンが形成される領域が現れたが,卓越波数は現れなかった.従って,デューンは形成されるものの特定の波長を持たないと考えられる.
  • 佐藤 博重, 泉 典洋
    理論応用力学講演会 講演論文集 2008年 
    河床の形態は河川の流れに大きな影響を与えるため,水理量に応じた河床形態を予測することは非常に重要である.特にデューンと呼ばれる小規模河床形態の発生や発達を説明する際には,デューンの発生に伴って局所的に大きな河床勾配が生じるため,流砂量に対する局所勾配の影響が重要になる.本研究では,重力による局所勾配の影響が考慮されたKovacs & Parker式に,この局所勾配の影響を低減させる機構として予想できる圧力勾配の影響の加味した掃流砂量式を用いて弱非線形安定解析を行った.本解析結果はデューン-平坦床遷移過程に亜臨界分岐が現れることを示し,実験結果によっても本結果は良好に説明できることを示した.
  • 中里 遥介, 泉 典洋
    理論応用力学講演会 講演論文集 2008年 
    Froude数がある程度小さいとき,水深の数割程度の波高を持つDuneと呼ばれる河床波が形成される. 特に流量が大きく変化する状況下では,河床形態は複雑な挙動を示す.Duneの形成により河道抵抗の増加,水位の上昇が起こるため,河川工学上Duneの発生メカニズムをより精確に知る必要がある.本研究では,河床高さの時間変化式に浮遊砂項を導入し,線形安定解析を行った.解析の結果,抵抗係数C-1が増加し浮遊砂が活発に生じるようになると,Duneの形成は抑制されることが理論的に明らかとなった.
  • 新岡 真治, 泉 典洋, 山口 健治, 阪口 秀, 渦岡 良介, 木戸 ゆかり
    理論応用力学講演会 講演論文集 2008年 
    実際に海底から土砂を採取し, その特性を明らかにしていくことを本研究の目的とする.実験で使用する泥は2006年6月7日に十勝沖の海底から採取してきた泥である。実験に使用する水路は, 高さ15cm, 幅8cm, 長さ200cmの長方形断面の管路である.実験結果によれば、無次元巻上げ速度式 Es=k(u*/ws)^n におけるkとnの値は n=1, k=1.2×10-3 となった。これは従来の実験で得られた値より小さい。また、水路中の塩分濃度を変化させてもkとnの値に変化はなかった。
  • 山口 健治, 泉 典洋
    理論応用力学講演会 講演論文集 2008年 
    海底の大陸棚周辺部には平行に一定間隔で並んだ無数の渓谷群が形成されており,陸上に形成される渓谷群と良く似た幾何学的形状を有していることが分かっている.これら海底渓谷群の主な成因として,海底面を流下する高濃度の浮遊土砂を含んだ密度流である乱泥流が考えられている.この乱泥流は海底を流下するとき,底面からの土砂の巻上げを行い,その浮遊砂濃度や流速を変化させるという特徴を持つ.このとき海底面は侵食されることになり,乱泥流は海底渓谷の成因となる.本研究では海底面の侵食作用に加え,層内への海水の取り込みを考慮に入れ乱泥流を定式化する.そして,線形安定解析の手法を用いて乱泥流による大陸棚上における海底渓谷の初期形成間隔について理論的に考察した.
  • 佐藤 希世, 泉 典洋, 吉川 泰弘, 安田 浩保
    理論応用力学講演会 講演論文集 2008年 
    環境に影響を与える窒素やリンなどの様々な栄養物質は洪水中の微細粒子に吸着されて輸送されることが明らかになり,浮遊微細粒子(Suspended Solid)の輸送が注目を集めることになった.今回の研究の目的は洪水時の河道内SSの供給源を解明し,流水中のSSと河床内土砂の相互作用(洗掘・堆積)の過程を考察することである.SSの挙動を把握するには流水中のSS濃度がどのような供給源から大きく影響を受けているのか検討する必要がある.また流水中のSSと河床内土砂の相互作用の過程の考察では河床上シルトの存在率と河床変動高を見ることで行った.大規模洪水では上流からのSS流入量と河床変動によって微粒子の堆積量が決まる.
  • 阪口 秀, 渦岡 良介, 泉 典洋, Kido Yukari
    日本地質学会学術大会講演要旨 2007年09月
  • A simple mathematical model of channel bifurcation  [通常講演]
    Proceedings of the 5th IAHR Symposium on River, Coastal and Estuarine Morphodynamics 2007年
  • Linear stability analysis of fluvial dunes and antidunes incorporating nonequilibrium bedload transport  [通常講演]
    Proceedings of the 5th IAHR Symposium on River, Coastal and Estuarine Morphodynamics 2007年
  • The formation of submarine gullies on continental shelves with arbitrary shapes by turbidity currents  [通常講演]
    Proceedings of the 5th IAHR Symposium on River, Coastal and Estuarine Morphodynamics 2007年
  • Weakly nonlinear analysis of the dune-flat bed transition with the mixing length turbulent model  [通常講演]
    Proceedings of the 5th IAHR Symposium on River, Coastal and Estuarine Morphodynamics 2007年
  • 佐藤 博重, 泉 典洋
    日本流体力学会年会講演論文集 2007年 
    Dunes formed in lower flow regimes disappear and antidunes appear when the discharge becomes larger than a certain amount during floods. It is important to elucidate the bed instability for the prediction of flow resistance of river channels. Colombini (2004) have performed linear stability analysis of fluvial dunes by the use of the mixing length turbulent model. In this study, we performed a linear stability analysis with the use of a sediment transport formula incorporating the influence of nonequilibrium bedload movement.
  • 大友 裕隆, 泉 典洋
    日本流体力学会年会講演論文集 2007年 
    A linear stability analysis is performed with the use of the Reynolds averaged Navier-Stokes equations and Darcy's law in order to investigate the instability of flow on permeable river beds. The spectral collocation method incorporated with the Chebyshev polynomials is employed in order to perform numerical solution of perturbed equations. It is found that, in the case of permeable beds, flow becomes unstable in the range of small Froude numbers where flow is stable in the case of impermeable beds.
  • 山口 健治, 泉 典洋
    日本流体力学会年会講演論文集 2007年
  • 水嶋 大樹, 泉 典洋, パーカー ゲーリー
    日本流体力学会年会講演論文集 2007年 
    This study proposes a simple mathematical model of channel bifurcation, in which a channel head is modeled by an opening on a flat plane composed of erodible bed material. A linear stability analysis is performed with the use of the depth-averaged momentum equations of flow and the Exner equation of beds subject to erosion. The analysis shows that channel bifurcation tends to take place as the discharge attracted by the channel head decreases.
  • 阪口 秀, 渦岡 良介, 泉 典洋, 木戸 ゆかり
    日本地質学会学術大会講演要旨 2007年
  • 泉 典洋
    日本流体力学会年会講演論文集 2006年 
    Weakly nonlinear stability analysis of fluvial dunes is performed with the use of the growth rate expansion method incorporated with the multiple scale parturbation technique. A series of perturbation equations are solved by the use of spectral collocation method with Chebyshev polynomial. The analysis reveals that the dune-flat bed transition is characterized by subcritical bifurcation when C^<-1> is large, where C is the friction coefficient.
  • The formation of beach cusps by waves with their crests parallel to shorelines  [通常講演]
    Proceedings of 4th IAHR Symposium on River, Coastal and Estuarine Morphodynamics 2005年
  • Inception of channelization on slopes with arbitrary shapes: erosional and depositional case  [通常講演]
    Proceedings of 4th IAHR Symposium on River, Coastal and Estuarine Morphodynamics 2005年
  • Weakly nonlinear analysis of dunes by the use of a sediment transport formula incorporating the pressure gradient  [通常講演]
    Proceedings of 4th IAHR Symposium on River, Coastal and Estuarine Morphodynamics 2005年
  • 山口 里実, 泉 典洋
    理論応用力学講演会 講演論文集 2005年 
    デューンの発生や発達を説明する際、流砂量式に局所勾配の影響をどう取り入れるかが従来課題となっている.著者らは、流砂量式に経験式を用いてデューンの弱非線型安定解析を行い,デューン_-_平坦床の遷移過程に見られる二価性やヒステリシスが解の亜臨界分岐に起因した現象であることを説明しているが、理論式であるKovacs&Parker式を用いると,重力による局所勾配の影響が効き過ぎるために亜臨界分岐が現れず、実現象を説明できない.本研究では,この理論式に圧力勾配の影響を加味し、再度デューンの弱非線型安定解析を試みた.その結果、重力による局所勾配の影響が低減し、理論式を用いても亜臨界分岐の現れることがわかった.
  • 水路頭部の分岐過程  [通常講演]
    泉 典洋
    理論応用力学講演会 講演論文集 2005年 
    水路頭部では周辺の流れが集まるため更に活発な侵食が生じ,水路は上流側へと発達していく.上流側へ発達する際,水路頭部は時折二つあるいはそれ以上の水路へ分岐することがある.このような分岐を幾度となく繰り返すことによって,最初単純だった水路群は複雑な水路網へと変化していく.本研究は,このような分岐が生じる原因が水路頭部周辺に生じる2次不安定現象であるとの観点から,水路頭部前縁部に円周方向の擾乱を与えることによって分岐の物理機構を理論的に説明したものである.解析の結果から,限界水深/抵抗係数と水路頭部半径の比が小さくなると,水路頭部は擾乱に対して不安定となり,分岐が生じ始めることが明らかとなった.
  • 島田 典和, 泉 典洋
    理論応用力学講演会 講演論文集 2005年 
    粘性土で構成された侵食が卓越する河床では,侵食が進行する際,水深よりかなり小さな規模の波状形状が形成されることがある.このような波状形状が塊状に剥離することによって急激に侵食が進行していく.本研究は,このような波状河床形状が侵食性河床上に形成されたリップルのようなものであるとの観点から,河床が擾乱に対して不安定となることを,線形安定解析の手法を用いて明らかにしたものである.解析によると,粘性底層の数十倍から数万倍の波長を持った擾乱に対して河床は不安定となり,数百倍から数千倍の範囲で擾乱の発達速度が最大となることが明らかとなった.
  • ポンプロミン アディチャイ, 泉 典洋, 辻本 哲郎
    日本流体力学会年会講演論文集 2004年 
    The existing linear stability analysis of incipient channellization was limited to the case of self-preserving slope profiles. In this study, the theory is extended to include the channellization on slopes with arbitrary shapes. Since arbitrary base state slope shape is evolving in time, the frozen time approach and the concept of momentary stability are employed. The analysis showed the possibility of channellization in the case of the arbitrary slope profile. It is found that the dominant wavelength decreases with increasing curvature of the slope.
  • 泉 典洋, 谷川 麻子, 田中 仁
    日本流体力学会年会講演論文集 2004年 
    Beach cusps are uniformly spaced, arcuate scallops formed at beaches. They are inseparably connected with nearshore current. The nearshore current system forms a vriety of circulation patterns, which have been attracting many researchers' interest since long time ago. While several theories have been proposed on formation nearshore current systems, Hino attributed their formation to the dynamic instability, and explained it in terms of liner stability analysis. In this study, his theory is revisited and improved in several aspects.
  • ピライラ シタン, 泉 典洋, 田中 仁
    日本流体力学会年会講演論文集 2004年 
    In most of the existing models of suspended sediment transport, the fine sediment is assumed to be abundant on the bed. This is not the case in most of actual rivers. Once most of fine sediment on the bed is removed from the bed, the entrainment rate is reduced due to the lack of fine sediment on the bed. This study proposes a new transport model of fine suspended solids in rivers. The model takes into account of the variation of the amount of fine particles on the bed by introducing an availability function and the continuity equation of fine particles on the bed. The model is applied to SS data obtained in a field observation during a small flood. It is found that the proposed model describes the behavior of the SS concentration considerably well compared with an existing model.
  • 島田 典和, 泉 典洋
    日本流体力学会年会講演論文集 2004年 
    In the erosion process of beds composed of cohesive clay, small waves are observed to be formed on the bed surface. In this study, a liner stability analysis of the formation of ripples on noncohesive beds is applied to the formation of small waves on purely erosional beds. The analysis reveals that flat beds become unstable, resulting in the growth of sinusoidal perturbations when the wavenumber is somewhere between 0.001 and 0.07. The characteristic wavelength is of 5-10 times the reciprocal of the shear velocity. The agreement between results of the analysis as well as an experiment are found to be reasonably good.
  • 泉 典洋, 藤井 健司
    日本流体力学会年会講演論文集 2003年 
    This paper presents a mathematical model of the formation of gullies on slopes composed of material having relatively weak cohesivity such as freshly deposited volcanic ash. A linear stability analysis is performed with the use of the momentum equations of flow, the dispersion equation of suspended sediment, and the Exner equation extended for beds subject to erosion and deposition of suspended sediment. The analysis shows that the dominant gully spacing is of the order of 1000 times the Froude-critical depth of the sheet flow on the slope. Evaluating the Richardson-critical thickness is of the order of 0.1 m, the spacing of gullies is of the order of 100m, which is equivalent to the spacing of gulleis formed on slopes composed of cohesive material.
  • 島田 典和, 泉 典洋
    日本流体力学会年会講演論文集 2003年 
    The purely erosional beds of steep are often characterized by a series of steps. In this paper, experiments were performed in order to study the formation and the evolution of the steps. In the experiments, the wavelength of steps were found to be of the order of six to sixty times the initial flow depth before the formation of steps. It was observed that the wavelengths reduced over time. The experimental results were compared with the theoretical results derived from a linear stability analysis. The agreement between theory and experiments were found to be good.
  • 山口 里実, 泉 典洋
    日本流体力学会年会講演論文集 2003年 
    Stage-discharge relations of flow in streams with movable beds are known to show hysteresis between on ascending and descending stages. In this study, a weakly nonlinear stability analysis is performed in order to provide a physical explanation for the hysteresis in the transition between dune and flat bed regimes. The growth rate expansion method with the multiple scale perturbation technique is applied to the two-dimensional Reynolds-averaged, Navier-Stokes equations and a sediment continuity equation. It is found that the dune-flat bed transition is characterized by the subcritical bifurcation in the case of steep channels. The theory suggests that suspended load reduces the critical Froude number.
  • 坂巻 隆史, PILAILAR Sitang, 泉 典洋, 西村 修
    日本水処理生物学会誌. 別巻 = Journal Japan Biological Society of Water and Waste 2002年10月 口頭発表(一般)
  • 山口里実, 泉典洋
    土木学会東北支部技術研究発表会講演概要 1999年03月
  • IZUMI N, TANAKA H, DATE M
    River Sediment Theor Appl 1999年
  • 軽部裕, 泉典洋, 池田駿介
    土木学会年次学術講演会講演概要集 第2部 1995年09月

その他活動・業績

受賞

  • 2013年09月 土木学会応用力学委員会 土木学会応用力学論文賞
     河床上昇・低下を伴う蛇行の線形安定解析 
    受賞者: 泉 典洋;青木章宜
  • 2012年 土木学会水工学論文賞
  • 2010年 土木学会水工学論文賞
  • 2006年 土木学会論文賞
  • 1995年 土木学会水工学論文奨励賞

共同研究・競争的資金等の研究課題

  • 火星北極冠に見られる螺旋状地溝の成因に関する研究
    研究期間 : 2011年
  • 水路網を伴う河口デルタの形成機構に関する研究
    研究期間 : 2011年
  • The formation of spiral troughs on the north polar cap of Mars
    研究期間 : 2011年
  • The formation of river mouth deltas with tidal channels
    研究期間 : 2011年
  • 塩水表面の凍結に伴い発生する対流と氷のパターン形成
    研究期間 : 2009年
  • 中規模河床波の形成機構に関する研究
    研究期間 : 2007年
  • 小規模河床波に関する研究
    研究期間 : 2001年
  • The formation of dunes and ripples
    研究期間 : 2001年
  • 海底乱泥流による海底峡谷の形成機構に関する研究
    研究期間 : 2000年
  • The formation of submarine canyons due to turbidity currents
    研究期間 : 2000年
  • 水路網の形成機構に関する研究
    研究期間 : 1993年
  • The formation of channel networks
    研究期間 : 1993年

教育活動情報

主要な担当授業

  • 卒業論文
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 工学部
  • 大学院共通授業科目(教育プログラム):PARE
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : エネルギー,バイオマス,水資源,地下水,通信ネットワーク,交通システム
  • インターンシップⅠ
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 工学部
  • Sediment Transport(土砂輸送特論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 : 河川,流域,土砂輸送,河床変動,河床形態,河床波,界面不安定,自己組織化,線形安定解析
  • インターンシップⅡ
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 工学部
  • 流域土砂管理工学特論
    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 : 河川,流域,土砂輸送,河床変動,河床形態,河床波,界面不安定,自己組織化,線形安定解析
  • 大学院共通授業科目(一般科目):複合領域
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : 風水害、雪害、土砂災害、火山災害、地震・津波災害
  • 大学院共通授業科目(教育プログラム):JICA開発大学院連携プログラム
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : Disaster prevention; Natural disaster; Flood; Heavy rainfall; Tsunami; Liquefaction; Earthquake; Japan’s ODA
  • Sediment Transport(土砂輸送特論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 : 河川,流域,土砂輸送,河床変動,河床形態,河床波,界面不安定,自己組織化,線形安定解析
  • 流域土砂管理工学特論
    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 : 河川,流域,土砂輸送,河床変動,河床形態,河床波,界面不安定,自己組織化,線形安定解析
  • 物理学Ⅰ
    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 : 運動、力、運動の法則、仕事、エネルギー、運動量、保存則、剛体、流体、単振動、音と光、干渉、回折
  • 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 : 都市,社会基盤,経済,海洋,地盤,橋梁,道路,鉄道,港湾,防災,河川
  • 水圏工学
    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 : 水循環,水文学,水資源工学,河川工学,河川環境,河川防災
  • 国際交流Ⅱ
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 国際本部
    キーワード : 水循環,水文学,水資源工学,河川工学,河川環境,河川防災
  • 技術者倫理学
    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 : 技術者倫理,倫理規定,土木技術史,倫理問題事例研究

大学運営

学内役職歴

  • 2019年4月1日 - 2021年3月31日 大学院工学院副学院長
  • 2019年4月1日 - 2021年3月31日 大学院工学研究院副研究院長

委員歴

  • 2017年 - 2019年   土木学会 論文集編集小委員会B1,2,3   委員長
  • 2016年 - 2018年   土木学会 応用力学委員会   委員長
  • 2011年 - 2013年   土木学会水工学委員会   河川部会部会長   土木学会
  • 2009年 - 2011年   土木学会   河川部会副部会長   土木学会
  • 2006年 - 2008年   日本流体力学会   代議員   日本流体力学会
  • 2005年 - 2007年   土木学会 応用力学委員会   幹事長   土木学会応用力学委員会
  • 2007年   土木学会   水工学委員会幹事   土木学会


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