EXPERIMENTAL-STUDY OF UNIFORM-SHEAR FLOW PAST A ROTATING CYLINDER

Abstract

An experimental study is made of two-dimensional uniform-shear flow (U=U-c + 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 less than or equal to Re less than or equal to 1,200, the shear parameter K[=GD/U-c] up to 0.15, and the value of the cylinder rotation parameter alpha[=omega D/2U(c)], -2.0 less than or equal to alpha less than or equal to 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 \alpha\ and K increase. When \alpha\ increases beyond a certain threshold value, the dominant frequency becomes less distinct. If \alpha\ 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 alpha are described The evolution of mean velocity profiles in the wakefield is depicted. Characterizations of the velocity profiles, as K and alpha vary, are made based on the measurement data.