低雷诺数串列双方柱流致振动质量比效应的数值研究

为澄清串列双方柱流致振动的质量比效应, 采用数值模拟方法, 在雷诺数为150时, 研究了质量比($m^{\ast }=3$, 10, 20)对下游方柱振动响应特性的影响规律, 分析了下游方柱尾流模态的演变过程, 探讨了导致下游方柱振动的流固耦合机制. 结果表明: 质量比对下游方柱的流致振动有重要影响, 低质量比($m^{\ast }=3$)时下游方柱的振动响应更为复杂, 随着折减速度的增大, 下游方柱并未出现传统“锁定”现象(即振动频率比$f_{y}$/$f_{\rm n} \approx1$的锁定), 而发生了“弱锁定”现象(即$f_{y}/f_{\rm n}<1$的锁定); 随着质量比的增加($m^{\ast }=10$和20), “弱锁定”现象消失, 而出现传统“锁定”现象, 且下游方柱横流向最大振幅减小. 质量比对串列双方柱的柱心间距有明显影响, 低质量比($m^{\ast }=3$)时的柱间距在振动锁定区内会急剧减小, 而较高质量比($m^{\ast }=10$和20)下的柱间距则变化不大. 此外, 质量比对串列双方柱的尾流模态和流固耦合机制也有显著影响, 其中低质量比($m^{\ast }=3$)下的情况更为多样. 

NUMERICAL INVESTIGATION OF MASS RATIO EFFECT ON FLOW-INDUCED VIBRATION OF TWO TANDEM SQUARE CYLINDERS AT LOW REYNOLDS NUMBER1)

To clarify the mass ratio effect on the flow-induced vibration of two tandem square cylinders, numerical simulation is employed to investigate the effect of mass ratio ($m^{\ast }=3$, 10, 20) on the vibration response characteristic of the downstream square cylinder at $Re=150$. The evolution of the wake modes are discussed, and the fluid-structure interaction (FSI) mechanism of the downstream square cylinder is analyzed as well. The results show that the mass ratio plays an important role in the flow-induced vibration of the downstream cylinder. When the mass ratio is small ($m^{\ast }=3$), the vibration response is very complicated for the downstream cylinder. With the increase of reduced flow speed, the downstream cylinder does not have the traditional lock-in phenomenon (with the lock-in frequency ratio around 1) but has the soft-lock-in phenomenon (with the lock-in frequency ratio less than 1). When the mass ratio is large ($m^{\ast }=10$ and 20), the soft-lock-in phenomenon disappears, while the traditional lock-in phenomenon occurs instead. The maximum transverse amplitude of the downstream cylinder decreases gradually with the increase of the mass ratio. Furthermore, the mass ratio has an obvious effect on the distance between two square cylinders. The distance between two cylinders severely decreases in the lock-in region for the small mass ratio but keeps almost constant for the larger mass ratio. In addition, the mass ratio also has a significant effect on the wake modes and FSI mechanisms of two tandem square cylinders. For the small mass ratio ($m^{\ast }=3$), the wake modes and the FSI mechanism are very diverse.