分区Lagrangian涡方法及瞬时起动圆柱初期流动的模拟

A ZONAL VORTEX METHOD AND IMPUL SIVELY STARTED FLOW AROUND A CIRCULAR CYLINDER

本文提出一种分区Lagrangian涡方法:将附着流动和分离流动分开处理,在附着区解边界层方层,只在分离区用涡方法解N-S方程。由于将尺度不同的区域分开了,求解分离区流动的涡方法中,每一时间步上物面引出的涡数在较小程度上依赖于Re数。这样,求解高Re数流动时,流场内的涡数,因而计算机内存和时间得以大大减小。用该方法计算了瞬时起动圆柱的初期流动,与实验结果比较相符很好。

In this paper, a zonal vortex method and its application to simulatingthe impulsively started flow of a circular cylinder are presented. This method treats the attached viscous flow region and the separated flow region separately- These two regions have length scales of O(Re-1/2) and O(1) respectively. The attached flow region is computed through solving boundary layer equations by finite difference method, which is fast and does not take large computer storage. Only the separated flow is computed by vortex method. Since the separated flow region has a length scale of O(1), in the vortex method used for this region, the number of new vortices introduced at the surface of the body pertime-step is relatively insensitive to the Reynolds number of the flow. For simulation of high Reynolds number flows with massive separation, the total number of vortices in the flow field, hence the computer-storage and computer-time is greatly reduced.