串列双圆柱绕流问题的数值模拟

Numerical simulation of flow past two cylinders in tandem arrangement

本文运用有限体积方法 ,对绕串列放置的双圆柱的二维不可压缩流动进行了数值计算。为研究两圆柱不同间距对圆柱间相互作用和尾流特征的影响 ,选取间距比L / D(L为两圆柱中心间的距离 ,D为圆柱直径 )在 1.5～ 5.0之间每隔 0 .5共八个有代表性的间距进行了计算模拟。计算均在 Re =2 0 0条件下进行。计算结果表明 :对该绕流问题 ,流动特征在很大程度上取决于间距的大小。且间距存在一临界值 ,间距比从小于临界值变化到大于临界值将带来一些流动动力学量的突然变化 ,如下游圆柱阻力系数Cd2 、两圆柱升力系数振幅 CL 以及 Strouhal数的突然增大等 (在间距很小的情况下 ,后一圆柱甚至会出现阻力系数为负的现象 )。反映涡脱落频率的 Strouhal数 ,对于上下游圆柱来说基本相同 ,尽管两圆柱后的涡脱落并非一致。

A finite volume method is employed to study the incompressible flow past a pair of cylinders at Re=200 in tandem arrangement. The dynamic characteristics of the unsteady incompressible laminar flow, especially the interaction between the two cylinders and the wake behind the downstream cylinder are investigated numerically. Computations are carried out at a Reynolds number of 200 where the near wake is predominantly two dimensional and laminar and vortex shedding is known to occur on the flow over a single cylinder. Eight cases with different separation distances between the cylinders are considered. The results are compared with flows past a single cylinder at corresponding Reynolds number and with experimental observations or numerical results by other researchers. It is observed that the qualitative nature of the flow depends strongly on the distance between the cylinder. In all cases, when the flow becomes unsteady, the downstream cylinder which lies in the wake of the upstream one, experiences very large unsteady forces. The Strouhal number, based on the dominant frequency in the time history of the lift coefficient, attains the same value for both cylinders.