单自由度串列双圆柱协同作用下的流致振动试验研究

Experimental Investigation on Flow Induced Motion of Single Degree-of-freedom Two Tandem Circular Cylinders

为揭示不同间距比(L/D)下串列双圆柱协同作用下的振动特性,采用自循环水槽对等直径协同运动的单自由度串列双圆柱进行了流致振动试验研究。试验所采用的串列双圆柱间距比L/D范围为1~5,雷诺数Re范围1×10~4~4×10~4,串列双圆柱质量比均为1.95。结果表明,L/D=1时,在试验Re范围内串列双圆柱产生较小幅度的振动;L/D=2时,串列双圆柱的振幅比A*在VIV上端分支初始段有陡降现象,其后随Re的增大,振幅持续增大同时频率开始下降,但测试范围内并未出现显著的驰振特征;L/D=3~5时,串列双圆柱随间距比L/D的增加,上游圆柱脱涡对下游圆柱的影响减弱,突显出单圆柱的"自限制"涡激振动特点。

Aiming at analyzing the response for longitudinal pitch ratio L/D = 1 to 5,the flow induced vibration on two tandem circular cylinders with single degree of freedom was investigated in a circulating water channel. Experiments with two tandem circular cylinders( mass ratio m*= 1.95) were conducted from Re = 10 000 to 40 000. The results indicate that for L/D = 1,the two tandem circular cylinders with single degree of freedom had no significant vibration in the experimental velocity range and the amplitude ratio was at low level. For L/D = 2,the amplitude ratio A*of two tandem circular cylinders with single degree of freedom has a steep drop at the earlier upper branch of VIV. After that,with the increase of Re,the amplitude ratio of two tandem circular cylinders has a consistent increase while the frequency has a slow drop. The significant galloping response has no found within the experimental range of velocity. For L/D = 3 to 5,with the increase of longitudinal pitch ratio L/D,the wake effect of the upstream cylinder to the downstream cylinder decreases and the two tandem circular cylinders with single degree of freedom vibrate is similar to a circular cylinder with a self-limited response.