有攻角方柱涡致振动的数值研究

Numerical simulation of the vortex-induced vibration of a square cylinder at the angle of attack

使用谱元法对弹性支承的有攻角方柱涡致振动进行了数值计算,分析了系统弹性刚度与质量比对振动响应的影响。数值计算得到了实验中发现的“高分支”。研究了质量比的影响,发现质量比对高分支的范围影响很大。对物体位移以及升力系数随时间变化曲线进行快速傅里叶变换,得到它们的频率组成。将质量比、系统刚度、以及不同主要频率成分组成一系列有效刚度。通过计算一系列不同系统刚度及质量比发现高分支大致分布在第一有效刚度大于零且第二有效刚度小于零的区域内。同时存在着一个临界质量,大于该质量,高分支消失。另外,还发现了高分支的基本频率可以是1/2 St,1/3St,1/4St。

Vortex-induced vibrations(VIV)of an elastically mounted square cylinder at the angle of attack were studied numerically using the spectral-element method to study the system response as a function of the spring stiffness and the mass ratio.The subharmonic mode of vibration dubbed the“higher branch”found in the experiment before was obtained.The effects of mass ratio were studied and it is found that the mass ratio has a great influence on the range of higher branch.The frequency contents of time traces of displacement and lift coefficient were obtained by taking Fourier transform.The main frequency contents,mass ratios and stiffness were composed into a series of effective rigidities.The higher branch exists in the regime that the first effective rigidity greater than zero and the second effective rigidity less than zero.There is a critical mass ratio and when the mass ratio is greater than that,the higher branch disappears.In addition,the fundamental frequency can be 1/2 St,1/3St,1/4St.