Vertical sorting process in oscillating water tank using DEM-MPS coupling model
Vertical sorting process in oscillating water tank using DEM-MPS coupling model
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DOI：
10.1016/j.coastaleng.2020.103765
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发表时间：
2020-08
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
在天然海滩，海床由分级沉积物组成。在冲浪带和碎波带，波浪作用导致沉积物的选择性搬运和分离。因此，在确定海滩上的沉积物输运速率和形态动力学时，需要考虑尺寸分离。然而，由于强烈的非线性和大变形的自由表面，以前的实验或观测调查未能获得足够的知识，分选过程中的冲洗区。在这项研究中，作为第一个调查步骤的大小分选过程中的冲带，实验进行了振荡水槽，而垂直分选过程进行了观察。此外，为了进一步研究流动和移动床的结构，进行了三维数值模拟。采用离散单元法（DEM）和移动粒子半隐式法（MPS）耦合的方法模拟了垂直分选过程。结果表明，垂向分选的发展导致了床面粗化和水平速度的转换。此外，作用力的调查显示，水面梯度的惯性引起的振荡的沉积物，其中包括元素，在水槽中，而导致频繁的元素碰撞和接触，这导致元素被向上推。
In natural beaches, sea-beds consist of graded sediments. In swash and surf zones, wave actions lead to selective transportation and segregation of sediments. Thus, size segregation needs to be considered while determining the sediment transport rate and morphological dynamics on beaches. However, because of the strong non-linearity and the large deformed free surface, previous experimental or observational investigations failed to obtain enough knowledge about the sorting process in the swash zone. In this study, as the first investigation step of the size sorting process in the swash zone, an experiment was conducted with an oscillatory water tank, while the vertical sorting process was observed. Moreover, to further investigate the structure of the flow and movable bed, a 3D numerical simulation was performed. A coupling scheme of the discrete element method (DEM) and the moving particles semi-implicit (MPS) method was applied to reproduce the vertical sorting progress. The result revealed that the development of the vertical sorting brought about bed surface armoring and a horizontal velocity transition. Additionally, an acting force investigation disclosed that the inertia of the water surface gradient induced oscillations of the sediments, which consisted of elements, in the water tank while leading to frequent element collisions and contacts, which caused the elements to be pushed upward.