The effect of suspension on mean velocity profile

The vertical gradient of suspended sediment concentration often exists in estuarine and coastal regions. The existence of such concentration gradient, particular that of cohesive suspended sediment concentration gradient, affects the flow velocity profile. Based on the wave-current full depth combined model, k-ε turbulent model is employed in this paper to simulate the effect of sediment concentration on the wave-current flow. A quantitative analysis of change mechanism of mean velocity profile is presented. The results show that the change mechanism of Eulerian mean current velocity under clear water is different from that under sediment-water mixed flow.     

Linear gravity waves on Maxwell fluids of finite depth

Linear surface gravity waves on Maxwell viscoelastic fluids with finite depth are studied in this paper. A dispersion equation describing the spatial decay of the gravity wave in finite depth is derived. A dimensionless memory (time) number 0 is introduced. The dispersion equation for the pure viscous fluid will be a specific case of the dispersion equation for the viscoelastic fluid as θ=0. The complex dispersion equation is numerically solved to investigate the dispersion relation. The influences of θ and water depth on the dispersion characteristics and wave decay are discussed. It is found that the role of elasticity for the Maxwell fluid is to make the surface gravity wave on the Maxwell fluid behave more like the surface gravity wave on the inviscid fluid.     

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。