Experimental Study of Uniform-Shear Flow Past a Rotating Cylinder

Abstract

An experimental study is made of two-dimensional uniform-shear flow (U = Uc + Gy) past a rotating cylinder of diameter D. A water-tunnel, equipped with a shear generator, was constructed. Laser-Doppler velocity measurements were undertaken to describe the wake characteristics. Data are compiled over the ranges of 600≤Re≤1,200, the shear parameter K[≡GD/Uc ] up to 0.15, and the value of the cylinder rotation parameter α[≡ωD/2Uc ], – 2.0≤α≤2.0. The power spectra of velocity measurements at downstream locations were analyzed to examine the vortex shedding patterns. In general, the dominant shedding frequency is shifted to a higher value as |α| and K increase. When |α| increases beyond a certain threshold value, the dominant frequency becomes less distinct. If |α| takes a value larger than around 1.5, the velocity field becomes randomized and diffuse, and the organized Karman vortex street activity weakens. The variations of the Strouhal number with K and α are described. The evolution of mean velocity profiles in the wake field is depicted. Characterizations of the velocity profiles, as K and α vary, are made based on the measurement data.