双圆柱斜向排列时旋涡脱落频率的实验研究

本研究用热线风速仪测量了斜向排列双圆柱的尾迹,并分析了尾迹中某些特征点上的速度频谱,从旋涡脱落频率的规律来研究双圆柱绕流相互之间的干扰。当两圆柱间距较远时,速度振荡的频率与单圆柱卡门涡街的频率相接近,随着两圆柱间距的接近,前、后圆柱各有其不同的旋涡脱落频率,且都不同于单圆柱旋涡脱落的频率。特别是当两圆柱处于某一相对位置时,出现双峰值的功率谱,其中一个峰值的频率大大地高于另一个峰值对应的频率,而且这两个峰值谁主谁副是不确定的,呈现出不稳定流动的特性。

AN EXPERIMENTAL STUDY ON THE VORTEX SHEDDING FROM TWO CIRCULAR CYLINDERS IN STAGGERED ARRANGEMENT

In this study,the velocity in the wake behind two circularcylinders arranged in staggered arrangement was measured with TSI hotwire anemometer.The spectra of velocity fluctuation at some locationsin the wake were made by FFT and the frequency of vortex sheddingwas obtained by spectrum analysis,The frequencies of vortex sheddingfrom upstream and downstream cylinders are different when two cylin-ders are not very close,and both frequencies are different from thevortex shedding frequency from single cylinder.Especially,a series ofdouble peak spectrum graphics have been found when two cylindersare arranged as L/d=2,Y/d=1,the frequency corresponding to the firstpeak ismuch lower than that of single cylinder, and the frequencycorresponding to the second peak is much higher than that of singlecylinde(?).It cannot be determined which one is the dominant peakbetween two peaks in the power spectrum graphics wherever the measur-ing locations in the wake and whenever the sampling time segment forFFT.The gap flow is unstable,sometimes two cylinders behave as asingle blunt body regarding to the vortex shedding,and sometimes thegap flow is strong.