An experimental study has been performed on the turbulent structure behind a circular cylinder immersed in a uniform shear flow by a specially designed wind-tunnel.
A grid was installed at X/H = 3 to obtain the lower turbulent intensity and free-stream condition. Experiments were performed under the condition of constant open-ratio of dampers. The centerline Reynolds number ($Re_c$) ranges from $10^3$ to 2 × $10^4$ and the shear parameter in terms of wind-tunnel ($K_H$) was varied from 0.40 to 0.54.
As results of present experiments, the free-stream of uniform shear flow becomes homogeneous with lower turbulent intensity, though the shear rate ($dU_f$/dy) is reduced remarkably. In the wake the maximum velocity defect was found to be at the lower velocity side of shear flow and the distribution of longitudinal turbulence is also asymmerical. Vortex shedding frequency depends on shear parameter, and it can be expressed as the frequency gradient parameter ($K_F$). According to our limited results of experiments, the Strouhal number of uniform shear flow seems to be higher than that of uniform flow.
