Accurate predictions of morphological changes in swash zones require a detailed understanding of sediment transport mechanisms, which are strongly related to bore-induced vortices and turbulence, surface-subsurface interactions, namely, infiltrate/exfiltrate flow, and swash-swash interactions. However, obtaining experimental or field measurements of instantaneous velocity and sediment flux is challenging owing to the suspended sediment, turbulence, and shallow depth characteristics of these regions. The present study simulates the gravel bedload transport under a dam-break bore at a grain-resolved spatial scale. The simulation uses a 3D Lagrangian–Lagrangian solid–fluid coupled model comprising the moving particle semi-implicit (MPS) method for a violent swash flow and the discrete element method (DEM) for gravels. The simulated water depth, velocity, and sediment flux agree with existing experimental results during a run-up. The gravel transport mechanisms for the lower, mid, and upper swash zones were discussed. Discussions on bedload mechanisms reveal that bore-generated horizontal vortices can reduce the onshore velocity near the beach surface, reducing sediment flux in the lower swash zone. Modified Shields numbers investigate the seepage effects: the frequently used standard Shields number value is insufficient to estimate bedload flux under the intense infiltration in the mid-swash zone. The simulation result also elucidates the turbulence characteristics in the upper swash zone.

中文翻译：

---

基于三维 DEM-MPS耦合的砾石分辨方案作用下爬升波作用


准确预测斜纹带的形态变化需要详细了解沉积物输运机制，这与钻孔引起的涡流和湍流、地表-地下相互作用（即渗透/渗漏流）以及斜纹-斜面相互作用密切相关。然而，由于这些区域的悬浮沉积物、湍流和浅深度特性，获得瞬时速度和沉积物通量的实验或现场测量具有挑战性。本研究在晶粒分辨空间尺度上模拟了溃坝孔下的砾石床载荷传输。该仿真使用三维拉格朗日-拉格朗日固-液耦合模型，该模型包括用于剧烈斜流的移动粒子半隐式 （MPS） 方法和用于砾石的离散元法 （DEM）。模拟的水深、速度和沉积物通量与助跑过程中的现有实验结果一致。讨论了下、中、上斜面区的砾石运输机制。关于床载机制的讨论表明，钻孔产生的水平涡流可以降低海滩表面附近的陆上速度，从而减少下斜区的沉积物通量。修正的 Shields 数研究了渗流效应：常用的标准 Shields 数值不足以估计中斜区强烈渗透下的床载通量。仿真结果还阐明了上斜盘区的湍流特性。