Computational investigation for sediment transport mechanism with wave breaking using Lagrangian model

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K04366
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 22040:Hydroengineering-related
• Research Institution: Kyoto University
• Principal Investigator: Eiji Harada 京都大学, 地球環境学堂, 准教授 (00362450)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 数値移動床 / 砕波

Outline of Final Research Achievements

A 3D DEM-MPS was developed based on fluid CFD analysis using the enhanced particle method and movable bed simulation using the discrete element method. The reproducibility of the developed DEM-MPS was confirmed by comparison with several moving bed experiments with free water surface fluctuation using a 2D wave-making channel and an oscillatory table. The numrical simulation results show that the inertia force contributes to the sediment transport as much as the drag force, and the accuracy of free water surface tracking is important for the prediction of sediment transport. In addition, it was confirmed that sediment transport was also active in the region of strong pore velocity, suggesting that the organized eddy structure near the surface of the movable bed is related to the pore velocity in the surface layer of the mobile bed.

Free Research Field

流砂水理学

Academic Significance and Societal Importance of the Research Achievements

砕波を含む激流条件下での底質輸送過程の検討は，それが非線形性の強い固液混相乱流現象であることから，観測や実験計測および数値シミュレーションの実施が困難である．本研究では，激しい自由水面変動を伴う条件におけるripple形成機構の一端を，水理実験およびDEM-MPSを用いた数値シミュレーションから検討した．砕破帯から波打ち帯で観察される土砂輸送機構を詳細に明らかにすることは、海浜変形計算の境界条件となる汀線付近の粗度予測に寄与する．したがって，海浜変形過程の予測精度の向上に役立つと期待される．