定常流中横向振动圆柱的升力突变现象研究

Study on the sharp change of lift force of a cylinder with transverse vibration in the steady flow

基于Realizablek-ε模型,采用有限体积法对亚临界雷诺数下(Re=105)受迫振动圆柱的涡激振动问题进行了二维数值研究,着重研究了振动频率与振动幅度两个参数对圆柱振动响应的影响,计算了三类振动频率:①共振强迫;②振动频率小于静止圆柱脱落频率;③振动频率高于静止圆柱脱落频率,并分析了尾流涡度模式与横向受迫振动圆柱升力系数的关系。数值模拟结果表明,三类振动频率模式下的动力响应差异明显,振动频率与振动幅度对圆柱的脉动升力系数影响较大。随着受迫振动振幅的增加,圆柱脉动升力系数出现了突变衰减,圆柱静止情况下的脱落频率与受迫振动频率控制的波动出现了相位逆变,使得圆柱与流体的能量传递出现了逆向改变。尾迹涡度模式反映了脉动升力系数的突变,其中的"2P"模式反映出共振条件下,升力系数在圆柱振幅处于中等范围时保持较小值且变化较小。

Based on Realizable k-ε model, the vortex-induced vibration(VIV) of a forced two-dimensional circular cylinder at subcritical Reynolds number(Re=105) is numerically studied by the finite volume method. Firstly, the influence of vibration frequency and vibration amplitude on the dynamic response of the cylinder are analyzed. Several oscillation frequencies are considered:(a)resonant forcing,(b)frequency below the natural frequency of the wake,(c)frequency above the shedding frequency of the wake. Meanwhile, the relationship between the wake vorticity mode and the fluctuating lift coefficient of the transverse forced vibration cylinder is analyzed. The numerical results show that the response of the three modes are obviously different. The vibration frequency and amplitude have a great influence on the fluctuating lift coefficient of the cylinder. With the increase of the amplitude of the forced vibration, the fluctuating lift coefficient of the cylinder decreases abruptly, and the phase inversion between the shedding frequency and the oscillation frequency occurs, which makes the energy transfer between the cylinder and the fluid reverse. The wake vorticity model reflects the sudden change of the fluctuating lift coefficient, and ?2 P? model is observed, which reflects that the lift coefficient keeps a small value and changes little in the range of medium amplitude in the resonant mode.