非对称波浪引起的薄层水流中沉积物微观力学的CFD-DEM研究
Sediment Micromechanics in Sheet Flows Induced by Asymmetric Waves: A CFD-DEM Study
摘要：
了解振荡流中的沉积物输运对于调查沿海地区的总体沉积物预算至关重要。在工程应用中，海岸线形态变化的预测是至关重要的。由于振荡流中的泥沙输运是稠密的颗粒流，因此颗粒相互作用的适当建模是至关重要的。虽然传统的双流体方法已被应用于振荡流中泥沙输移的研究，但这些方法没有解决颗粒之间的相互作用。振荡水流中泥沙运动的颗粒分辨模型和泥沙颗粒的细观力学研究还很缺乏。在这项工作中，一个并行的CFD-DEM求解器，可以解决颗粒间的碰撞被应用于研究泥沙颗粒在振荡流中的细观力学。利用粗砂和中砂的试验数据对CFD-DEM求解器的计算结果进行了验证。与试验结果的比较表明，用该模型计算的流速、输沙通量和净输沙率是令人满意的。此外，详细介绍了沉积床的微观力学量，包括Voronoi浓度、配位数和颗粒相互作用力。结果表明，这些细观力学量在振荡周期的不同阶段的变化是显着的，这是由于不同的床的响应。为了研究沉积物床的结构特性，Voronoi体积分数和配位数的相关性进行了比较，从流化床模拟的结果。结果表明，尽管流态不同，但输沙和流化床的微观结构相似。
英文摘要：
Understanding the sediment transport in oscillatory flows is essential to the investigation of the overall sediment budget for coastal regions. This overall budget is crucial for the prediction of the morphological change of coastline in engineering applications. Since the sediment transport in oscillatory flows is dense particle-laden flow, appropriate modeling of the particle interaction is critical. Although traditional two-fluid approaches have been applied to the study of sediment transport in oscillatory flows, the approaches do not resolve the interaction of the particles. Particle-resolved modeling of sediment transport in oscillatory flows and the study of micromechanics of sediment particles are still lacking. In this work, a parallel CFD-DEM solver that can resolve the inter-particle collision is applied to study the granular micromechanics of sediment particles in oscillatory flows. The results obtained from the CFD-DEM solver are validated by using the experimental data of coarse and medium sands. The comparison with experimental results suggests that the flow velocity, the sediment flux and the net sediment transport rate predicted by are satisfactory. Moreover, the micromechanic quantities of the sediment bed are presented in detail, including Voronoi concentration, coordination number, and particle interaction force. It is demonstrated that variation of these micromechanic quantities at different phases in the oscillatory cycle is significant, which is due to different responses of the sediment bed. To investigate the structural properties of the sediment bed, the correlation of the Voronoi volume fraction and coordination number are compared to the results from the fluidized bed simulations. The consistency in the comparison indicates the structural micromechanics of sediment transport and fluidized bed are similar despite the differences in flow patterns.
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