有限长度钝体尾流的三维特性

运用X形热线,对高宽比分别为3,5和7的有限长度方形截面柱体尾流进行测量,并运用相平均方法对其尾流场进行研究.相关实验是在一低湍流度风洞中,雷诺数Red为3 500的条件下进行的.研究结果表明:壁面边界层与柱体自由端面后的下降流造成了柱体尾流显著的三维性;该三维性在柱体下游10d(d为柱体的宽度)处仍能清晰的观察到;对于高宽比为3的柱体,相平均的脉动速度以及脉动速度能谱在所有测量高度上均近似相同;而高宽比为5或7时,尾流中间高度附近流动周期性最强,且相平均脉动速度最大值为柱体顶部或底部附近对应值的2倍以上.

Three dimension characteristics of finite-length bluff body wake

The wake flow behind a finite-length cylinder with aspect ratio of 3,5 and 7 was measured using X-wire.Phase-averaged technique was applied.All experiments were conducted in a low-speed wind-tunnel at Red=3 500.It is found that the boundary layer on the wall and the free-end downwash flow make the near wake highly three dimensional.This three-dimensionality is clearly observed at 10d(d is the cylinder width) downstream from the cylinder.For H/d=3,the phase-averaged fluctuation velocity and the power spectra...