双圆柱斜置排列时下游圆柱压力分布和振荡频率的实验研究

当两个圆柱斜置排列并靠得较近时,绕流下游圆柱的流动明显地不同于单一圆柱.本文研究了下游圆柱压力分布受到的影响,并着重于用FFT来分析圆柱表面某些特征点上的压力频谱,研究频谱与圆柱之间的相对距离和位置的关系.当圆柱间距较远时,压力振荡的频率与单圆柱卡门涡节的频率相接近,随着横向间距的接近,频率逐渐降低,然而当两圆柱十分接近时,外侧压力振荡的频率继续降低,但圆柱内侧压力振荡的频率却突然提高,出现了一个圆柱体两侧作用有不同频率压力的情况.

An Experimental Study About the Pressure Distribution and Fluctuating Frequency of Downstream Cylinder When Two Cylinders Are in Staggered Arrangement

Two cylinders with the same diameter in staggered arrangement, if they are very close, the flow field around the downstream cylinder is different from a single cylinder apparently. In this paper, the pressure distribution on the side face of the downstream cylinder is measured with a pressure transducer. The spectrum analysis for pressure of the downstream cylinder are made with a/d converter and a personal computer. The power spectrum are varied with the relative location and distance between two cylinders. When one cylinder is far from the other one, the frequency of fluctuating pressure acting on the downstream cylinder is very closed to the shedding frequency of Karmann vortex street of single cylinder, but the frequency is decreased when the distance between two cylinders is approached in lateral gradually. However, when the another cylinder was arranged very closely at front right, for example in this study, the distance between the centers of two cylinders is twice of the diameter of the cylinder in the flow direction and one diameter in lateral, a higher frequency with a slightly wider frequency band was found in the power spectrum of pressure at the side faced to the front cylinder, but the fluctuating frequency of pressure acting on the side faced to outside is decreased as usual. Two frequencies are different from which shedded from single cylinder. This means that two opposite sides of downstream cylinder are acted by the pressure with two different frequencices.