串列三圆柱的尾流特性及涡激振动研究

Wake Characteristics and Vortex-induced Vibration of Three Cylinders in Tandem

采用重叠网格技术,研究了低雷诺数下串列三圆柱的尾流特性及中游圆柱横向振动的涡激振动响应。结果表明,对于静止三圆柱在不同节径比(2.0~6.0)下的流场,随着节径比的增大,尾流模态将从“2S”模式变为“2P”模式;其上游圆柱与下游圆柱的涡脱临界节径比在3.0~3.5之间,中游圆柱的涡脱临界节径比在2.5~3.0之间;对于上下游圆柱固定-中游圆柱可横向振动的串列三圆柱,其中游圆柱产生横向振动的原因是发生了结构模态失稳。虽然中游圆柱在涡脱临界节径比前后的振动响应趋势相同,但是在临界节径比之后的情况将以更高的折减速度进入锁频状态,且锁频区间更宽。

At low Reynolds number,the wake characteristics of the three cylinders in tandem and the vortexinduced vibration response of the midstream cylinder are studied by using the overlapping grid technique.It is found that for flow field analysis under different pitch-to-diameter ratios(2.0~6.0)of stationary three cylinders,the wake mode changes from‘2S’to‘2P’with the increase of pitch-to-diameter ratio.The critical pitch-todiameter ratio of the upstream cylinder and the downstream cylinder is between 3.0~3.5,and the midstream cylinder is between 2.5~3.0.For the three cylinders where the upstream cylinder and downstream cylinder are fixed and the midstream cylinder can vibrate laterally,the lateral vibration of the midstream cylinder is caused by the structural mode instability.Although the vibration response trend of the midstream cylinder vortex is the same before and after the critical pitch-to-diameter ratio,it will enter the frequency locking state at a higher reduction speed and the lock-in range is wider,after the critical pitch-to-diameter ratio.