交互砂州の流下速度の低下要因について  [in Japanese] ON THE DECREASING FACTOR OF ALTERNATE BARS CELERITY  [in Japanese]

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Abstract

本研究では,交互砂州の流下速度が低下するときの力学機構について,模型実験における水面と水底面の同時計測手法STを用いて取得した時空間的に高密度な定量情報に基づいて考察した.STの計測値より算出した水面勾配ベクトルおよび無次元掃流力τ<sub>*w</sub>から,交互砂州の流下速度が低下する要因が砂州波高<i>H<sub>B</sub></i>の発達に伴う流れの迂回により砂州前縁部への掃流砂の供給が途絶えたことであることが示唆された.さらに流下方向の縦断底面勾配<i>i</i>と流路幅方向の横断底面勾配<i>j</i>が交互砂州の流下特性や発達状態を判定する指標となる可能性を示唆した.

 In this research, we verified dynamic mechanism when celerity of alternate bars decreases using spatial and temporal high density qualitative information of measured water surface and bed surface. As a result of Non-dimensional shear stress and vector of water surface gradient which calculated by measured water level, we confirmed the factor of decreasing celerity is that bedload in bar front decreases. Deceasing of bedload in bar front is caused by meandering of flow and bedload involved in increasing of wave height. Finally, we indicated longitudinal bed slope <i>i</i> and cross bed slope <i>j</i> can be index to evaluate develop conditions and flow-down characteristics of alternate bars.

Journal

  • Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering)

    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 74(4), I_1111-I_1116, 2018

    Japan Society of Civil Engineers

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