过渡流下异管径三圆柱绕流的可视化实验

Visualization Experiment on the Flow Passed Three Circular Cylinders with Different Diameters in Transitional Flow

为研究过渡流下不同雷诺数Re,不同横向中心距Ps的异管径三圆柱绕流的流动特性,采用二维粒子图像测速系统(PIV)对过渡流下异管径三圆柱绕流进行可视化实验研究。结果表明,Re=120、150和200时,横向中心距的变化对上下游圆柱尾流有着明显影响。横向中心距的变化主要影响上下游圆柱的互相作用,从而引起尾流旋涡形态的变化。在研究的工况中,随着横向中心距的增大,上下游圆柱尾流的旋涡尺度逐渐减小,下游小圆柱前的时均速度越来越小,从而降低了有效雷诺数。

In order to study the flow characteristics of flow around three circular cylinders at different Reynolds Numbers and dif⁃ferent transverse center distances in transition flow,a two-dimensional particle image velocimetry system(PIV)was used to com⁃plete the flow visualization.The results show that,the flow characteristics of the wake of upstream and downstream circular cylin⁃ders wakes are related to the change of transverse center distances obviously at Re=120、150 and 200.The change of transverse center distances mainly affects the interaction between upstream and downstream circular cylinders,resulting in the change of vortex structure.According to this study,with the increase of the transverse center distances,the vortex scale of the upstream and downstream circular cylinders wakes decreases gradually.Meanwhile,the time-mean velocity in front of the downstream small circular cylinder becomes smaller and smaller,which reduces the effective Reynolds Numbers.