不同截面形状对流致振动特性影响的试验分析

Experiment alanalysis on characteristics about fow-inducedvibration of bluff body with different section shapes

为了比较不同截面形状钝体的流致振动特性,找到适用海流能转换装置的柱体截面形式,在水槽中开展了不同折合速度下,相同质量比和相同特征长度的圆形、菱形、方形、梯形、类梯形、T字形6种不同截面形状钝体在水槽中的流致振动试验.试验结果表明:类梯形、梯形、T字形、方形截面获得的振幅响应较大,其振幅随着折合速度增加而不断增加,表现为驰振特征.发生驰振时,不同截面的振动频率却比较稳定,随折合速度的变化不大;棱形和圆形截面获得振幅响应较小,随着折合速度的增加而不断减小,表现为涡激振动下端分支特性,振动频率随着折合速度的增加而增大;6种截面的振幅响应从大到小依次为类梯形、梯形、T字形、方形、菱形、圆形.研究发现不同截面的振动响应大小主要跟截面在流场中分离点的位置、截面后沿部分面积占比及附加质量等因素有关.

In order to find the most suitable cross-section shape for the ocean current energy conversion,experiments in circulating water channels were carried out to identify the influence of different bluff body shapes on the characteristics of the flow-induced vibrations.Six different cross-sections,circular,square,diamond-shaped,trapezoidal,trapezoid-like,T-shaped cross-sections,with the same mass ratio and the same characteristic length were chosen in this experimental study.The experimental results show that the amplitude responses of trapezoid-like,trapezoidal,T-shaped and square cross-sections are large,and the amplitude increases with the increase of reduced speed,which is characterized by galloping.When galloping occurs,the vibration frequencies of different sections are relatively stable,and change little with the reduced speed.The amplitude responses of cylinder and rhombus are small and meet the characteristics of lower branch of VIV,the responses decreasing and frequencies increasing with the increase of the incoming flow.The amplitude responses of the six cross-sections in decreasing order are trapezoid-like,trapezoidal,T-shaped,square,diamond-shaped,circular.The vibrations of different sections are mainly related to the position of separation point of the boundary layer,the proportion of the back edge area,and the added mass.