圆球绕流场的尾涡分析和升阻力研究

Numerical investigations of wake and force for flow past a sphere

采用自编的分块算法程序模拟了雷诺数在20～1000之间的圆球绕流场。在Re=25时捕捉到流动分离,与试验结果一致。对Re=250时稳态非对称尾流区内流体的输运情况进行研究,证实圆球绕流场中纵向对称面的存在。对于非稳态流动,主要研究了阻力和横向力的时间变化规律,并分析了频谱特征。计算发现横向合力主要在横截面上两个很窄的区间内偏移。经过几种不同涡定义方法的优劣测试,本文采用Hunt等人介绍的Q-定义方法对非稳态绕流场的尾涡结构进行了直观描述。

Flow past a sphere is studied using 3D DDM (Domain Decomposition Method). Flow separation is caught at Re = 25. For Re = 250, the transportation of fluid in the wake behind the sphere is visualized and a plane of symmetry is observed. The time histories and spectrum characteristics of the drag and the lateral force acted on the surface of the sphere are investigated. The dynamical characteristic of the lateral force is absent in many simulations of the flow past a sphere. The Q-definition proposed by Hunt is picked from several frequently used definitions of a vortex to identify the unsteady vortical regions behind the sphere.