过渡流下近壁插入圆柱流动特性的实验研究

Experimental Study on Flow Characteristics of Wall Interpolated Cylinder Under Transitional Flow

为研究间隙比对近壁单圆柱绕流结构的影响,解明圆柱尾流对壁面不稳定性的作用机理,搭建了开式循环水槽实验台,通过粒子图像测速(PIV)系统,对过渡流下近壁单圆柱模型进行了实验研究。结果表明:Re=300时,间隙比对圆柱绕流结构和壁面扰动强度影响明显。间隙比较小时,圆柱下游剪切层发展被抑制;随着间隙比的增加,圆柱尾流开始形成旋涡对,且旋涡对尺度逐渐减小并趋于对称;同时,近壁区域流体的加速效果先增强后减弱,加速区域不断增加,壁面流动不稳定性先增强后减弱。相比于无壁面影响的单圆柱,近壁单圆柱尾流形成了周期更长的旋涡交替脱落运动,增强了壁面流动的不稳定性。

In order to study the influence of clearance ratio on the flow structure of near-wall single cylinder and reveal the mechanism of cylinder wake on wall instability,an open circulating flume experimental rig was set up.The near-wall single cylinder model under transitional flow was experimentally studied is carried out using particle image velocimetry(PIV).The results show that the clearance ratio has an obvious effect on the flow structure and wall disturbance intensity around the cylinder at Re=300.When the gap is relatively small,the development of the shear layer downstream of the cylinder is suppressed;with the increase of the gap ratio,the cylindrical wake begins to form a vortex pair,and the scale of the vortex pair gradually decreases and tends to be symmetrical;at the same time,the acceleration effect of the fluid near the wall increases firstly and then weakens,and the wall flow instability increases at first and then weakens.Compared with the single cylinder without wall effect,the wake of the single cylinder near the wall forms a longer period of vortex alternating shedding motion,which enhances the instability of the wall flow.