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

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, equ ipped with a shear generator was constructed. Laser-Doppler velocity m easurements were undertaken to describe the wake characteristics. Data are compiled over the ranges of 600 less than or equal to Re less tha n or equal to 1,200, the shear parameter K[=GD/U-c] up to 0.15, and th e 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 spec tra of velocity measurements at downstream locations were analyzed to examine the vortex shedding patterns. In general, the dominant sheddin g frequency is shifted to a higher value as \alpha\ and K increase. Wh en \alpha\ increases beyond a certain threshold value, the dominant fr equency becomes less distinct. If \alpha\ takes a value larger than ar ound 1.5, the velocity field becomes randomized and diffuse, and the o rganized Karman vortex street activity weakens. The variations of the Strouhal number with K and alpha are described The evolution of mean v elocity profiles in the wakefield is depicted. Characterizations of th e velocity profiles, as K and alpha vary, are made based on the measur ement data.