分流板对圆柱绕流湍流结构演化影响的实验研究

The experimental investigation on the effects of the splitter plate on the evolution of turbulent structures in flow around a circular cylinder

采用粒子图像测速(Particle Image Velocimetry,PIV)技术实验研究了带分流板的圆柱绕流流动特性,分析了分流板对圆柱绕流湍流结构演化特性的影响。雷诺数为3.9×10^(3),分流板长度L与圆柱直径D之比L/D为0~2.50。实验结果表明,随着L/D从0增大至1.00,圆柱后方回流区长度和回流区面积显著增大;当L/D>1.00时,L/D对圆柱后方回流特性的影响较小。分流板影响圆柱绕流湍流结构的演化特性:当L/D<1.00时,分流板抑制尾涡脱落,斯特劳哈尔数Sr减小,L/D从0增大至1.00,Sr减小了26.34%。此外,圆柱尾涡在分流板后缘诱导形成旋转方向相反的二次涡,二次涡沿分流板向上游运动。1.00≤L/D<2.00时,分流板作用于圆柱尾涡,尾涡发生破碎,形成一些小尺度尾涡。L/D≥2.00时,尾涡附着于分流板上,二次涡主要分布于圆柱后方。随着L/D增大,分流板减小了圆柱后方的湍流脉动强度。

The flow characteristics of a circular cylinder with a splitter plate are investigated experimentally with Particle Image Velocimetry(PIV),and the effects of the splitter plate on the evolution of turbulent structures in the flow around the cylinder are examined.The Reynolds number is Re=3.9×10^(3),and the ratio of the splitter plate length L to the cylinder diameter D is L/D=0~2.50.The results show that the length and the area of the recirculation region significantly increase as L/D increases from 0 to 1.00,and the effects of L/D on the characteristics of the recirculation flow behind the cylinder are small for L/D>1.00.The evolution of turbulent structures is affected by the splitter plate.For L/D<1.00 the shedding of the wake vortex is suppressed by the splitter plate,and the Strouhal number(Sr)is decreased.As L/D increases from 0 to 1.00,there is a 26.34%decrease of Sr.In addition,the cylinder wake vortex induces the formation of the secondary vortex with opposite direction of rotation in the trailing edge of the splitter plate,and the secondary vortex moves upstream along the plate.For 1.00≤L/D<2.00,the splitter plate interacts with the cylinder wake vortex,and the wake vortex breaks down into some small-scale wake vortices.For L/D≥2.00,the wake vortex is reattached on the splitter plate,and the secondary vortex is mainly distributed behind the cylinder.As L/D increases,the splitter plate reduces the intensity of turbulence fluctuations behind the cylinder.