Influence of Inlet Shear on Structure of Wake behind a Square Cylinder

Abstract

The force coefficients and the frequency of vortex shedding in the wake of a square cylinder exposed to a uniform shear flow and the flow structure around it were numerically investigated. The Reynolds number defined on the basis of cylinder width was in the range of 250–1,500. The shear parameter, namely the transverse velocity gradient, which is nondimensionalized using the obstacle width and the average incoming velocity, was varied between 0 and 0.2. Analyses were performed for a number of flow parameters using various combinations of Reynolds number and shear parameters. Results show that mean and root-mean-square values of drag coefficient initially decrease up to certain values of the shear rate and then increase with increase in shear parameter. The root-mean-square values of lift coefficient show a similar behavior. The Strouhal number decreases uniformly with increase in shear parameter. At higher shear rates, the von Kármán vortex street comprising alternating vortices breaks, and the far wake shows mainly clockwise vortices.