Numerical investigation of drag force on flow through circular array of cylinders

A 2-D model for flow through a circular patch with an array of vertical circular cylinders in a channel is established using the Navier-Stokes equations with a hybrid RANS/LES turbulence model–the Scale Adaptive Simulation (SAS) model. The applicability of the model is first validated by test cases where experimental data are available for comparison with the computed results. It is verified that the present model can predict well the average velocity and turbulence structure. The drag force and drag coefficient are then calculated using the present model for a number of cases with different solid volume fractions, cylinder Reynolds numbers and patch diameters. It is shown that the drag coefficient increases with increasing solid volume fraction, but decreases with increasing Reynolds number. However, the drag coefficient is independent of the diameter of circular batch when the solid volume fraction and Reynolds number are kept constant.     

基于动网格技术对泥沙输运和局部冲淤的数值模拟

该文建立泥沙输运和床面冲淤的垂向二维模型,采用SST k-ω模型模拟湍流并使用VOF法处理自由面运动,同时用动网格技术实现水底地形变化,计算了水平射流的泥沙冲淤问题。流场和地形变化的计算结果与实验数据基本一致,从而验证了计算模型的可靠性。在此基础上,该文进一步研究动床条件下的带横向沟槽明渠流动中水底地形随时间的变化过程。结果表明,水流在上坡过程中,由于水深减小流速增大,上坡部分受到局部冲刷作用;而坡顶处由于泥沙沉积形成一个小沙丘,坡顶位置在来流作用下逐渐向下游推移,最终地形趋于平衡状态。     

泵站矩形及蜗形进水池的水力特性数值模拟

泵站进水池作为泵站的重要进水建筑物,后壁平面形状对水泵的进水流态和水泵的工作效率都有一定的影响。此文应用CFD技术,将流速均匀度和流量作为水泵性能评估的依据,设定了多个设计工况,对矩形后壁、蜗形后壁以及水面加设隔板后水流的流态进行了数值计算,系统地分析了各工况下的进水池内的流动特性,揭示了矩形和蜗形进水池水流流动的水力性能差异,对类似进水池的设计和改造具有一定的参考意义。