下游圆柱涡致振动的升阻力特性及涡脱落模态分析

采用分块耦合方法结合任意拉格朗日欧拉法数值求解非定常二维不可压缩NS方程和Poisson
方程，分析了下游圆柱涡致振动的涡脱落模态以及升阻力特性。圆柱振荡频率比值为0.30～1.49。分析了
各种模态之间相互转化的跃迁点、升力与振幅间相位和模态间转化的关系，以及初始涡量形成的差异与模
态间转化的关系，研究了当涡脱落向下游移动时的演化和重组现象。研究发现，涡的横向和流向间距以及
涡街的大小随频率比的变化而变化；存在3种典型的涡脱落模态，即2P、2S 和 P+S模态，各种模态之间相
互竞争从而促进了流体与结构间相互作用的发展。

Forces and wake patterns of downstream oscillating circular cylinder induced by vortex shedding

The vortex shedding from vortex-induced vibration on downstream circular cylinder was studied by numerical simulations of the two-dimensional incompressible unsteady NS and Poisson equations. The domain decomposition method (DDM) incorporating the arbitrary Lagrangian-Eulerian (ALE) method was adopted. The frequency ratio varied from 0.30 to 1.49. The transitions between different wake states were investigated. The magnitude and phase shift of the lift force corresponding to mode alterations in both near the cylinder and the whole flow wake were also investigated. Then, the vortex reorganization and evolvement in the wake of the downstream cylinder due to the nonlinear instability were studied. The results show that accompanying the variations in frequency ratio were changes in the separation distance and the width of the vortex wake. Three wake modes, 2S (single), 2P (pair) and P S, were observed competing actively in enhancing the interaction between the fluid and structure.