单向流作用下近壁面圆柱的流向振动

在单向流水槽中对近壁面圆柱体的流向振动进行了实验模拟。分析了圆柱流向振动位移时程曲线,探讨了圆柱振动频率随水流速度的变化特征。研究了圆柱振动幅值和频率的变化特性,结合圆柱尾迹涡的变化规律,分析了流向振动的起因。实验结果表明:随着流速的增加,圆柱流向振动经历了发生、发展和消失的变化过程,振动频率呈现出缓慢增长的趋势;在流向振动触发初期和后期衰退时,流向振动频率存在多值现象,频谱中呈现多个谱峰;圆柱流向振动所对应的约减速度范围明显小于横向涡激振动所对应的范围。

Streamwise vibration of a near-wall cylinder exposed to unidirectional flow

The streamwise vibration of a cylinder near a plane boundary under the action of unidirectional flow was modelled experimentally in a flume. The time history curve of the cylinder vibration displacement was measured, and the variation of vibration frequency with flow velocity was examined. The characteristic of vibration amplitude and frequency of the cylinder was analyzed. The causes for the occurrence of streamwise vibration were discussed, in correlation with the characteristic of wake vortex. The experimental results indicate that the streamwise vibration experiences an occurrence-evolution-disappearance process with the increasing flow velocity. At the initiation and decay stages of the streamwise vibration, there exist multiple values of vibration frequency, i.e. multiple spectrum peaks appear at the frequency spectrum. The range of reduced velocity (Vr) corresponding to streamwise vibration is much less than that for transverse vibration.