The passive control of three-dimensional flow over a square cylinder by a vertical plate at a moderate Reynolds number

This paper presents three-dimensional simulation results to investigate the reduction of fluid forces acting on a square cylinder by a passive control method, i.e. placing a vertical control plate upstream of the cylinder. The simulations were carried out for Re W = 500, based on the width of the square cylinder (W) and the inlet flow velocity. The width of the control plate (h) varied between 0.1W and 0.9W and the distance between the control plate and cylinder (S) was set in the range of 1.1W–5W. The flow patterns, vortex shedding frequency, and wake vorticity structures were studied to determine the flow instabilities that existed over the square cylinder and control plate. In addition, the reduction of mean and fluctuating fluid forces acting on the square cylinder in the presence of a control plate was studied, and compared with the single square cylinder in order to identify optimum conditions. The results indicated that the case with h = 0.7W and 2.5W ≤ S ≤ 3W emerged as optimal, offering the highest reduction in the fluid forces that occurred over the square cylinder.