双圆柱尾流致涡激振动的质量比效应及其机理

双圆柱尾流激振受多种因素影响,情况复杂,质量比m*(相同体积的圆柱与流体质量的比值)对双圆柱尾流激振的影响规律尚未澄清。采用数值模拟方法,在低雷诺数下(Re=100),研究了三种质量比(m*=2,10,20)对串列双圆柱尾流致涡激振动特性和尾流流场结构的影响规律,分析了下游圆柱的升力与位移的相位差,探讨了涡激升力与能量输入的内在联系。结果表明:质量比对串列圆柱尾流致涡激振动有重要影响。随着质量比的增大,横流向最大振幅减小,并发生在较小折减速度下,振动锁定区域范围变窄;质量比越小,升力与位移之间的相位差对下游圆柱振幅的影响越显著;在较小质量比时尾流出现“2S”、不规则和平行涡街模态,而在较大质量比时只有“2S”和平行涡街模态。

Effects of mass ratio on wake-induced vibration of two tandem circular cylinders and its mechanism

The wake-induced vibration of two cylinders is complicated and affected by many factors.The mass ratio,which is the ratio of the system mass and the mass of the displaced fluid,has significant influence on the wake induced vibration of two tandem cylinders.However,the effect of the mass ratio has not been clarified.Numerical simulation is applied to study the wake-induced vibration of two circular cylinders in tandem arrangement.Three different mass ratios,m*=2,10 and 20,are examined to identify the effect of mass ratio on the vibration characteristics of the wake-induced vibration and wake flow structures of the twin tandem circular cylinders at Re=100.The phase difference between the lift and displacement of the downstream cylinder is analyzed.The internal relationship of the downstream circular cylinder between the vortex-induced lift force and the energy input is also explored.The results display the mass ratio has a significant influence on the wake-induced vibration of twin circular cylinders in the tandem arrangement.As the increased of mass ratio,the maximum amplitude in transverse direction decreases,and it occurs at a relatively small reduced velocity,and the lock-in area for the vortex-induced vibration of the downstream cylinder narrows.With the decrease of the mass ratio,the influence of the phase difference between lift and displacement on the amplitude of the downstream cylinder is more remarkable.Wake flow structures such as′2S′,irregular and parallel vortex street mode appear at the smaller mass ratio.However,only′2S′and parallel vortex street mode appear,when the mass radio is large.