Drag reduction by the effect of rounded corners for a square cylinder

Abstract

Flow around square cylinders has been studied via unsteady simulations done at a Reynolds number of Re = 100. In the present study, the effects of rounded corners on different flow characteristics have been evaluated. The main influence of rounded corners has been considered for various ratios (r*) up to 0.45 in terms of drag coefficient values. Flow stagnation points have been obtained in front of the square cylinders. These points constitute the maximum pressure. The cluster sizes for cross-stream velocity components are nearly the same. Viscous flow generates vortices around the top and bottom edges of the square cylinder. The produced vortices have been affected by the wake region. When moving away from the bodies, streamwise velocity profiles have been influenced by the variation of the rounded corner ratios. The wake region has shrunk owing to the rounded corners, and the drag reduction has been provided. The drag coefficient (CD) has been obtained as 1.418 for r* = 0. As a result of increasing the ratio for the rounded corners, drag coefficients decreased for the square cylinders. The percentage values are 4.6%, 7.2%, 8.4%, 9.6%, 11.1%, 11.9%, 12.5%, 13.3%, and 14.3% for the drag decrement from r* = 0.05 to r* = 0.45 when compared to the reference value. The most effective value for drag reduction has been attained as 4.6% for the ratio of rounded corners in a row. Even though the decrement percentage tends to increase by enhancing the ratio of the rounded corners, the increment rate indicates the decreasing trend.