明渠层流近床面颗粒拖曳力研究

泥沙颗粒受到的拖曳力是泥沙运动的主要驱动力，而当前应用于计算流体力学-离散颗粒法(CFD-DPM)耦合模型进行水沙运动模拟的泥沙颗粒拖曳力公式均没有考虑明渠流底床边壁作用的影响。求解不可压缩Navier-Stokes方程，对明渠层流不同雷诺数条件下床面附近不同高度处颗粒所受拖曳力进行了模拟，根据模拟结果变化规律，提出了综合考虑床面和水流惯性对标准拖曳力影响的修正拖曳力计算公式。与常用的单颗粒标准拖曳力公式和考虑遮蔽效应的多颗粒拖曳力公式相比，采用本文修正公式得到的水沙作用力更接近高精度数值解，应用于CFD-DPM输沙模拟获得的输沙结果与输沙率公式结果一致，应用分析表明输沙模拟应当采用粗糙底床边界。

Drag force of particle near bed in laminar open channel flow

Drag force is the main driving force of sediment movement under water.At present,the drag force formulae used in a coupled model of CFD-DPM (Computational Fluid Mechanics-Discrete Particle Method) for water and sediment simulation near bottom,do not consider the effect of sediment bed-induced wall effect.The drag forces of particles at different heights away from the bottom wall under different Reynolds numbers in laminar open channel flow were simulated.Based on the simulated forces,a modified formula for the drag force of a sediment particle near bottom under the combined influence of bottom boundary and fluid inertia in laminar open channel flow was fitted.Compared with two commonly used formulas in CFD-DPM,the standard drag force of a single particle and the uniformly hindered drag forces for multiple particles,the fitted formula produced better simulation results when compared with high-resolution reference values.When used in sediment transport simulation,the transport rate simulated by the fitted formula agrees with empirical formula prediction.The application analysis indicates that sediment transport simulation must be conducted above a rough bottom.