雷诺数对不同展弦比下长平板绕流湍流特性影响的实验研究

An experimental study on the effect of Reynolds number on the turbulent characteristics of a rectangular cylinder with different aspect ratio

利用粒子图像测速(PIV)实验研究了不同展弦比下,雷诺数对长平板绕流的影响。雷诺数为:Re=500、800、1000,平板板长L与厚度D的比值为L/D,L/D=3、6。实验结果表明,展弦比L/D=3时,流体从平板前缘分离后重新附着在平板尾缘处。展弦比L/D=3和6时,平板上方再附着长度及平板后的回流区长度会随着雷诺数的增大而增大,展弦比为6时,雷诺数对板上分离泡的影响较小。雷诺数和展弦比会影响流场的湍流特性。展弦比L/D=3时,雷诺数的增加会导致平板两侧的脉动强度增加,而板后的脉动强度减弱;随着展弦比L/D增加,流场的湍流脉动强度减小。同时随着雷诺数的增加,流场中的小尺度涡结构增加。

The particle image velocimetry(PIV)experiment was used to investigate the effect of Reynolds number on the flow around a long plate with different aspect ratio.The Reynolds number is Re=500,800 and 1000,respectively,and the ratio of plate flow length L to thickness D is L/D=3 and 6.The experimental results showed that when the aspect ratio was L/D=3,the fluid was separated from the leading edge of the plate and then re-attached to the trailing edge of the rectangular cylinder.When the aspect ratio was L/D=3 and 6,the length of the separation bubble above the plate and the reflux zone behind the plate increased with the steady build up of Reynolds number,and when the aspect ratio was 6,the influence of Reynolds number on the separation of bubbles on the plate was relatively small.Reynolds number and aspect ratio affected the turbulence characteristics of the flow field.When the aspect ratio was L/D=3,an increase in Reynolds number would lead to an increase in the pulsation intensity on both sides of the plate,while the pulsation intensity behind the plate would decrease.In addition,the turbulence fluctuation intensity of the flow field would decrease with the increase of the aspect ratio.At the same time,the smallscale vortex structure in the flow field increased with the increase of Reynolds number.