不同翼片扰流特性的PIV对比实验

利用粒子成像测速（PIV）技术对圆管内置梯形翼片后方流场进行了测量，分析了翼片迎流（UFW）和顺流（DFW）两种放置方式对流场的扰动特性。结果表明，迎流翼片形成的涡沿周向延展范围较大，持续性好，涡偶内侧为向壁流；顺流翼片形成的涡沿径向延展范围较大，在较短距离内扰动较为明显，涡偶内侧为背壁流。两种流动结构都能有效提高壁面附近的速度分量，促进主流和壁面附近流体的质量交换。随着Reynolds数增大，纵向涡的稳定性减弱，在Re=3000时，翼片的扰流效果均较好。

PIV experiment on turbulence characteristic with different winglets inserted

The velocity fields in the circular tube with trapezoid-winglets inserted were investigated by particle image velocimetry (PIV) technique and the turbulent characteristics induced by different arrangement winglets were also compared. The results showed that swirling flow induced by the up-flow winglets extent along the radial direction and had greater intensity as well as better persistence. Inside vortex pair the flow was to the wall direction while outer vortex pair the flow was away from the tube wall, which flow pattern was inversed for the down-flow winglets. In addition, the swirling flow induced by down-flow winglets extent more along the circumference direction and the disturbance effect was obvious in a short distance downstream the winglets. Both swirling flow patterns could disturb the near wall region flow, destroying the velocity boundary layer and notably improving the velocity component normal to the mainstream, which lead to the intensification of the transverse mixing action and mass transfer in the tube. As the Reynolds number increasing, the dissipative interaction between the two flow layers was enhanced, decreasing the stability of longitudinal vortex. In a certain range of Reynolds numbers involved in the experiment, it could be drawn that both arrangement winglets showed better disturbance effect when Re=3000.