靠近排列的两个交错方柱三维绕流的数值模拟

NUMERICAL SIMULATION OF 3D VISCOUS LAMINAR FLOWAROUND TWO SQUARE CYLINDERS IN CLOSELY STAGGEREDARRANGEMENT

通过用时间分裂算法求解Navier－Stokes方程,对中等Reynolds数下靠近排列的两个交错方柱三维绕流进行了数值模拟,其中,中间速度场用四阶Adams格式计算,压力场通过结合近似因子分解方法AF1与稳定的双共轭梯度方法Bi-CGSTAB进行迭代求解．数值模拟发现当两个方柱靠得较近时,有互相吸引趋势,而且上游方柱的Strouhal数较大．方柱的交错排列方式对绕流影响明显．计算结果与实验定性吻合,而且比用MAC－AF1方法计算的结果好．

The transient 3D viscous laminar flow around two identical square cylinders in closelystaggered arrangement at moderate Reynolds numbers has been simulated numerically by solvingthe incompressible Navier-Stokes equations with a fractional algorithm, where the fourth orderAdams scheme were used to evaluate the intermediate velocity field, and the AF1 (approximatefactorization one) as well as the stablized bi-conjugate gradient (Bi-CGSTAB) algorithm werecombined to obtain the pressure field by solving the derived pressure Poisson's equation, fromwhich the velocity at the new time level was evaluated. It was found that, when the squarecylinders are closely stagger arrangement, the values for the spanwise-averaged mean lift indicatethat the hydrodynamic forces due to vortex motion will make them attracted each other. Inaddition, the Strouhal number for upstream cylinder is found larger than that for the downstreamone. The stagger arrangement appears a significant effect on the flow pattern. The results obtainedin the current study are qualiatively in a good agreemeat with experiments, and more elegantthan those obtained by MAC-AF1 method.