Numerical investigation of sediment transport mechanism under breaking waves by DEM-MPS coupling scheme
Numerical investigation of sediment transport mechanism under breaking waves by DEM-MPS coupling scheme
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DOI：
10.1016/j.coastaleng.2022.104146
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发表时间：
2022-05
影响因子：
4.4
通讯作者：
T. Tazaki;E. Harada;H. Gotoh
中科院分区：
文献类型：
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作者：
T. Tazaki;E. Harada;H. Gotoh
在海滩的碎浪和冲浪区的关键沉积物输运机制中，冲浪产生的漩涡悬浮了大量的沉积物，随着时间的推移，海滩形态发生了重大变化。由于涡旋和泥沙输移的不连续性和局部性，在实验室试验或现场调查中很难测量流场和泥沙浓度，使得这种研究对于研究海滩泥沙输移或作为预测海滩形态变化的基础的价值有限。本文试图通过对破碎波作用下泥沙输移机理的颗粒尺度数值研究来克服这些不足。采用离散单元法（DEM）和移动粒子半隐式法（MPS）耦合的方法对模型进行了三维数值模拟，并与小型波浪水槽试验结果进行了对比，验证了模型的有效性。数值模拟结果揭示了波内泥沙运动规律以及波生压力梯度对涟漪脊附近泥沙输移的贡献。在空间尺度上的单个泥沙颗粒相关联的旋涡，湍流，并施加力附近的涟漪槽的泥沙输运机制进行了研究。结果表明，在水面上产生的旋涡的冲击波影响的床料运动主要是通过一个大的压力梯度力的作用，由于床面附近的局部最小压力，这可以与一个涡区。
Plunging waves generate vortices that suspend significant amounts of sediment in the key sediment transport mechanism in the surf and swash zones of beaches, causing major changes in the beach morphology over time. The intermittency and locality of vortices and sediment transport make it difficult to measure the flow fields and sediment concentrations in laboratory experiments or field investigations, making such studies of limited value for studying the sediment transport at beaches or as a basis for predicting changes in beach morphology. An attempt is made in this study to overcome these shortcomings through a particle-scale numerical investigation of sediment transport mechanisms under breaking waves. The numerical simulation was performed using three-dimensional coupling of the discrete element method (DEM) and moving particle semi-implicit (MPS) method, with the validity of the numerical model confirmed by comparison with experimental results obtained in a small wave flume. The numerical results revealed the intra-wave sediment motion and the contribution of the wave-generated pressure gradient to the sediment transport near the ripple crest. Sediment transport mechanisms was investigated at the spatial scale of the individual sediment grains by associating it with the vortices, turbulence, and exerted forces near the ripple trough. The results revealed that vortices generated at the water surface by plunging waves affected the bed material motions mainly through the action of a large pressure gradient force that arises near the bed surface owing to a local minimum of pressure, which can be associated with a vortex region.