Reynolds number effects on three-dimensional flow control over a square cylinder

Abstract

In this article, the effects of Reynolds number on three-dimensional flow over a square cylinder with flow control are discussed at moderate Reynolds numbers, i.e. ReW = 200–1000 (based on the width of the square cylinder and the inlet flow velocity). The flow is controlled by a thin vertical plate placed upstream of the cylinder. The vorticity structures at different Reynolds numbers, turbulent kinetic energy, Reynolds stresses, and mean and fluctuating fluid forces on the square cylinder in the presence of the control plate are investigated in order to determine the characteristics of the transient flow regime at the wake region behind the square cylinder. The results show that the transitional process of the flow regime from laminar to turbulent in the wake region behind the square cylinder at ReW = 300–600 causes the pulsation phenomena to happen in the instantaneous lift signals of the square cylinder, and both of spanwise instability modes of A and B, as well as the dislocation phenomena are presented in the wake region behind the cylinder. It is also found that the mean and fluctuating fluid forces of the square cylinder in the presence of the control plate decrease in comparison to the single square cylinder, except for the rms drag coefficient at ReW = 300.