Search Results 1-20 of 60

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  • Experimental Examination of Two-layer Model for Debris Flows  [in Japanese]

    山上 路生 , 長坂 香織 , 岡本 隆明

    … In the mild slop situation, it is similar to open-channel flow with bed-load transport. … Between them, we can see a two-layer current composed of an upper clearwater layer and a lower highly-concentrated sediment layer. … The present study focuses on this two-layer debris flows and examine previous theory of velocity profile comparing with measured data in a short-fetch narrow flume. …

    京都大学防災研究所年報. B = Disaster Prevention Research Institute Annuals. B 63(B), 306-311, 2020-12

    IR 

  • ESTIMATION METHOD FOR FLOW DISCHARGE AND BED LEVEL/GRIAN SIZE DISTRIBUTIONS USING OBSERVED WATER LEVEL AND ONE-DIMENSIONAL NUMERICAL MODEL OF GRAVEL TRANSPORT  [in Japanese]

    SHIGE-EDA Mirei , AKIYAMA Juichiro , KANAYA Ryo , KATSURA Yuuki

    <p> 本研究は,従来の流量ではなく,比較的容易に観測が行える水位を境界条件とした1次元砂礫河床変動モデルを用いた水面形,流量,混合砂礫河床の河床位,流砂量,河床材料の粒度分布の時空間変化を推定する手法を構築するとともに,混合砂礫河床での実験結果に基づき,その予測精度について検討したものである.本研究から,水位を境界条件とした本手法は,流量を与条件とした従来の方法と同程度の精度で,直線 …

    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 75(2), I_889-I_894, 2019

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  • Study on setting of saturation concentration of suspended sediment in numerical simulation of sediment transport associated with tsunami for off Takahama Bay  [in Japanese]

    MURAKAMI Yoshikane , SHIKATA Takemi , TONOMO Koji , SUGAWARA Daisuke , HIRAISHI Tetsuya

    掃流砂層と浮遊砂層の交換砂量を考慮した津波移動床モデルのうち,高橋ほか(1999)の手法においては,飽和浮遊砂濃度が計算結果に与える影響が大きく,その設定方法の高度化が課題となっている。本研究では,関西電力高浜発電所の基準津波を用いて,既往の研究事例よりも広域の計算領域を対象に,藤井ほか(1998)および高橋ほか(1999)の手法により,飽和浮遊砂濃度を時空間的に一定の定数として与えた場合の地形変 …

    Journal of Japan Society for Natural Disaster Science 37(2), 165-176, 2019

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  • METHOD TO EVALUATE LONGITUDINAL SEDIMENT SORTING FOCUSING ON SEDIMENT TRANSPORT MECHANISM  [in Japanese]

    HARADA Daisuke , EGASHIRA Shinji

    <p> ネパール国ウエストラプティ川では,僅かな区間内で顕著な河床材料の分級が生じている.本研究は流砂機構の違いに着目して,この分級現象を説明しようとするものである.一般に適用されているような流砂量式を用いてウエストラプティ川で見られるような河床材料及び流砂の縦断分級を説明することは難しい.そこで,河床材料の評価方法として掃流砂層厚を,また無次元掃流力の5/2乗に比例する掃流砂量式を導 …

    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 74(5), I_907-I_912, 2018

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  • THE PROCESS OF DEFORMATION OF THE CLAY BED WITH SUPPLYING SAND IN THE CURVED OPEN CHANNEL  [in Japanese]

    SEKINE Masato , SATO Yu , ASHIZAWA Honami , YOSHIKAWA Fumitaka

    <p> 本研究では,上流側から掃流砂として輸送されてきた砂礫が,河道湾曲部の粘土河床上で生じる浸食・堆積のプロセスに及ぼす影響を実験的に明らかにすることを目指した.ここでは,給砂量や通水時間を様々に変化させた一連の系統的な実験を行った.実験の結果,輸送されてくる砂礫の量の違いにより,粘土河床の変動のプロセスに変化が現れ,次のような特徴的な河床構造となることがわかってきた.砂礫の接触に伴 …

    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 74(5), I_931-I_936, 2018

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  • SEDIMENTARY STRUCTURE OF NON-UNIFORM SAND UPSTREAM AND DOWNSTREAM OF DAM OR WEIR IN MEANDERING RIVER UNDER UNSTEADY HYDROGRAPH  [in Japanese]

    SATO Takahiro , OTA Kazuyuki , ARAI Ryosuke

    <p> 蛇行河川に設置されたダム堰の上下流における混合砂の堆積構造を調べるため,移動床実験と平面二次元河床変動解析において同一波形の非定常ハイドロを連続して与え,ダム堰上流が満砂になるまでの堆積過程とダム堰下流への土砂流出による洗掘・堆積過程を調べた.実験では水位変化と河床位平面分布を測定するとともに,河床堆積物の粒度鉛直分布測定とX線CT撮影を行った.計算では流砂層モデルを用いて,ダ …

    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 74(5), I_1135-I_1140, 2018

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  • EVALUATION ON THE BOTTOM SHEAR FORCE IN STREAMWISE CANYON IN AN ARMORED BED ACTUALLY RELATED TO THE MOVEMENT OF THE SAND  [in Japanese]

    SAKATA Ryosuke , TANAKA Norio

    ダム下流河川など粗粒化した河床構造空間における土砂の移動には,巨礫・大礫で形成される粗度層内における流下方向の礫間空隙(流れが加速される空間:縦キャニオン)が重要な役割を果たす.同空間の底面せん断力を明らかにすることを目的として,粗度の流下方向間隔に注目して,風洞実験を行った.実験の結果,流下方向の粗度間隔が広いほど,底面近傍の流れが加速され対数分布に近くなり,逆に粗度間隔が狭まるにつれて,くの字 …

    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 73(4), I_787-I_792, 2017

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  • HYSTERESIS OF DYNAMIC EQUILIBRIUM BED COMPOSED OF FIXED BED AND MOVABLE BED  [in Japanese]

    KYUKA Tomoko , TAKEBAYASHI Hiroshi , FUJITA Masaharu

    … This study focuses on the hysteresis of dynamic equilibrium bed composed of fixed bed and movable bed. … By experimental results, the irreversibility of bed deformation between the movable and fixed beds was observed. … By supplying sediment, in a rate lower than the equilibrium rate from the upstream, the bed was widely exposed. …

    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 71(4), I_889-I_894, 2015

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  • VERTICAL STRUCTURE OF THE DYNAMIC EQUILIBRIUM STATE OF RIVERBED WITH LARGER STONES  [in Japanese]

    HIRAMATSU Yuki , SEKINE Masato , KENMOTSU Naoki

    … Experimental investigation was conducted on the dynamic equilibrium state of bed which was composed of extremely wide range of sediment. … A void of larger stones was filled with medium gravel which moves as bed load and finer sand which moves as suspended load. … The layer of only gravel was exposed on the bed surface under the condition that the discharge of sand was small. …

    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 71(4), I_865-I_870, 2015

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  • LES-BASED COMPUTATIONAL STUDY ON FRICTION FACTOR UNDER COARSE-GRAINED SHEET-FLOW  [in Japanese]

    HARADA Eiji , TSURUTA Naoki , GOTOH Hitoshi

    … は,数値漂砂力学的に漂砂量を検討する観点から,振動流下シートフロー漂砂を対象に粒子流のLESを実施する.底面せん断応力の位相変化に対応した摩擦係数の推移から,シートフロー層の下層に存在するimmobile bed表層の摩擦係数には,境界層外縁流速に対する位相の進みが示され,また固定床表層と比較してimmobile bed表層の摩擦係数は,粒子混入による流速の低下により増加する傾向が示された. …

    Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 71(2), I_493-I_498, 2015

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  • FIELD SURVEY OF BED MATERIAL EXCHANGE THICKNESS ON DIFFERENT RIVER BED TYPE  [in Japanese]

    YANO Masaaki , WATANABE Yasuharu , YABE Hiroki , WATANABE Kazuyoshi

    … For the purpose of understanding the thickness of riverbed material exchange at multiple places with different bed topography, we conducted cross-section surveys, gravel size surveys and buried markers surveys in the Toyohira River before and after snowmelt flooding. …

    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 70(4), I_1003-I_1008, 2014

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  • SEDIMENT TRANSPORT CALCULATION CONSIDERING COHESIVE EFFECTS AND ITS APPLICATION TO WAVE-INDUCED TOPOGRAPHIC CHANGE OF SHALLOWS  [in Japanese]

    NAKAMURA Tomoaki , CHO Yong-Hwan , MIZUTANI Norimi , LEE Kwang-Ho

    砂粒子の間隙に粘土が含まれることによる粘着力の効果を導入した漂砂計算手法を提案するとともに,それを組み込んだ波と地形変化の相互作用を解析できる数値計算モデルを構築し,浅場の地形変化現象への適用を通じてモデルの妥当性の検証と粘着力の効果の感度分析を行った.その結果,砂粒子の間隙に粘土があることによる効果は限界Shields数を大きくするだけでは表せず,粘着力の効果を適切にモデル化することの重要性を示 …

    Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering) 69(2), I_1036-I_1041, 2013

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  • EFFECT OF SAND TRANSPORT ON DEFORMATION OF BED WITH COHESIVE SEDIMENT  [in Japanese]

    SEKINE Masato , OKA Yukihiro , NOMURA Masakazu

    … The purpose of this experiment is to understand the effect of sand transported from upstream reach of river on both deformation of bed with cohesive sediment and vertical bed structure. … In this experiment, the amount of sediment feeding is equal to the amount of equilibrium bed-load transport, and experiment was continued until the deformation of the bed reaches the dynamic equilibrium state. …

    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 69(4), I_1027-I_1032, 2013

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  • Modeling 3D Numerical Movable Bed based on LBM and its Application to the Analysis of Bed-Load Layer  [in Japanese]

    HE Lulu , OKAJIMA Masashi , KIOKA Wataru , KITANO Toshikazu

    … The three-dimensional lattice Boltzmann method (LBM) is used to simulate the behavior of bed-load layer in open channel shear flow. … The present simulation predicts well the behavior of each particle in the bed-load layer both in saltation and sheetflow regimes. …

    Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 69(2), I_546-I_550, 2013

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  • NUMERICAL MODEL FOR GRAVEL TRANSPORT AND ITS APPLICABILITY TO BED DEGRADATION AND AGGRADATION WITH ARMOURING AND DOWNSTREAM FINING  [in Japanese]

    SHIGE-EDA Mirei , AKIYAMA Juichiro , SAKAMOTO Hiroshi

    … The model employs relation for hiding and bed-load transport of mixtures of Ashida and Michiue (1972) and Wilcock and Croew (2003) and links grain size distributions in the bed load, surface layer and subsurface with the gravel transfer function. … The model was applied to experimental data of a bed degradation and aggradation with armouring and downstream fining. …

    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 68(4), I_1189-I_1194, 2012

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  • Examine of Manning's coefficient and the bed-load layer for one-dimensional calculation of bed variation  [in Japanese]

    吉川 泰弘 , 渡邊 康玄

    Monthly report (662), 11-20, 2008-07

    IR 

  • EFFECT OF SHAPE OF SEDIMENT SIZE DISTRIBUTION AND MATHEMATICAL MODELS TO REPRODUCE SEDIMENT SIZE ON SPATIOTEMPORAL CHANGE CHARACTERISTICS OF ALTERNATE BAR GEOMETRY

    TAKEBAYASHI Hiroshi , EGASHIRA Shinji

    … Effect of shape of sediment size distribution on alternate bar geometry is discussed by use of linear bed stability analysis and numerical analysis. … The results show that bar geometry on bed with bimodal type sediment has large difference from the others. … Furthermore, bed load layer model is applied for reproduction of alternate bars and compared the results to those by exchange layer model. …

    PROCEEDINGS OF HYDRAULIC ENGINEERING (52), 595-600, 2008

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  • Relationship between Characteristics of Sediment Transport and Physical Environment in Riffles  [in Japanese]

    CHIBANA Takeyoshi , HAYASHI Toru , MIYAKE Motofumi

    河川物理環境の改善には,土砂動態の把握が不可欠である.そこで,早瀬内の微生息場が形成される過程を,土砂動態の観点から調べることとした. <BR>解析では,空間スケールの階層性に注目し次の三段階の過程に注目した.まず,土砂供給量が砂州の発達度を決定し早瀬形状が決まる過程,次に早瀬形状が決まり,その内部の水深・流速分布や河床形状が決まる過程,さらに早瀬内部での水理環境が決まった結果,砂の動 …

    JOURNAL OF JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES 20(4), 362-372, 2007

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  • A new treatment of the exchange layer thickness to evaluate sediment sorting and armoring

    Luu Xuan Loc , 江頭 進治 , 竹林 洋史

    Journal of Applied Mechanics, JSCE 9, 1025-1030, 2006

  • A new treatment of the exchange layer thickness to evaluate sediment sorting and armoring

    LUU Xuan Loc , EGASHIRA Shinji , TAKEBAYASHI Hiroshi

    … This study presents a new treatment of an exchange layer to evaluate the sediment sorting and armoring process. … In this treatment, a thickness of bed load layer is evaluated as a function of bed shear stress, and is introduced into a well known exchange layer model which firstly proposed by Hirano (1971). …

    Journal of applied mechanics (9), 1025-1030, 2006

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