【作者】 邹建锋； 任安禄； 邓见；

【Author】 ZOU Jianfeng, REN Anlu, DENG Jian, Chen Wenqu (Department of Mechanics, Zhejiang University, Hangzhou 310027, P. R. China)

【机构】 浙江大学力学系流体工程研究所；

【摘要】 本文把Goldstein等人提出的虚拟边界法推广到三维情况,研究了Re=250时不同间距比下串列双圆球的绕流场。研究发现,在小间距比(L/D≈1.5)的情况下,由于上下游圆球尾流区的相互抑制消除了压力不稳定性,整个流场呈现稳态轴对称特征。间距比为2.0时,周向压力梯度诱发出流体的周向输运,流场呈现稳态非对称性,但流场中存在特定的对称面。间距比增大到2.5后,绕流场开始周期振荡,原有的对称面依旧存在。文中详细研究了间距比为3.0时的流场三维特征,给出了一个流动周期内的涡结构脱落情况,发现下游圆球上表面的涡脱频率为下表面的2倍频。进而对上下游尾流场频谱特征的分析明确的给出了不同间距比下占优频率的竞争机制。间距比增至7.0时,整个流场恢复稳态特征,两圆球尾部同时出现双线涡,这时流场对称面的位置发生了变动。本文的绝大多数数值结果在浙江大学工程与科学计算中心的SGI Origin3900并行机上完成,在此致谢。更多还原

【Abstract】 The virtual boundary method is extended to 3D application and used to simulate the flow field of two spheres in tandem arrangement for Re=250. The numerical results show that for small gaps (L/D≈1.5), due to the mutual suppress between the wakes of the two spheres, the full flow field is stable and axisymmetric. As the gap is increased to 2.0, the azimuthal pressure gradient induces the azimuthal fluid flow and an asymmetric but stable flow is constructed through a certain bifurcation. The flow field has a planar symmetry at gap 2.0. For L/D≥2.5, the vortices are periodically shed from the top and bottom sides of the downstream sphere, but the planar symmetry persists. The case for L/D=3.0 is investigated in detail. The vortical structure and the flow topology on a few typical cross sections along the axis are presented, respectively. The shedding frequency of the top side of the downstream sphere is found to double of the frequency of the bottom side. With the flow spectra of various gaps given, the underlying competitive mechanism between two dominated frequencies is revealed. For larger gaps (L D>7.0). the flow field recovers the stable state but the position of the symmetric plane rotates with an angle of 45°. All these numerical computations were performed on an SGI Origin3900 machine at the Center for Engineering and Scientific Computation of Zhejiang University.更多还原