Effect on Flow Characteristics around a 3D Square Cylinder with Corner Codifications

Abstract

The flow behavior around a square cylinder of finite height placed on a surface gets effected by application of corner modifications. The aim of current simulation based research is to investigate the effect of applying two corner modifications i.e. corner chamfer and corner radius, on the turbulent wake region which is formed behind the square cylinder and understand the effect various corner modifications have on the flow characteristics., The study also involves the understanding of how the wake region is improved by applying corner modification and, thus, decreasing the vibrations induced by the passing flow and improving structural integrity. The formation or horseshoe vortex (HSV) and its characteristics are also a part of this study in order to observe the effect on HSV by introducing corner modification. Two types of medications were applied i.e. corner chamfer and corner radius with various ratios. For corner chamfer, the ratio 0.1d, 0.2d and 0.3d were studies where d=0.0127m i.e. the width of the cylinder. Radius ratio from 0.1d to 0.5d (circular cylindrical) were applied and flow behavior was observed. Aspect ratio for the cylinder was kept at 4 for all cases and Reynold Number (Re) was kept at 12,000. Investigations were carried out using Improved Delayed Detached Eddy Simulation (IDDES) turbulence model in Fluent in order to note the effect on flow characteristics focusing on the turbulent wale around the wall mounted square cylinder by introducing various corner modifications. The simulation results were then validated against already performed wind tunnel experiments at Re=12,000 having similar geometry. Results were compared for various horizontal and vertical planes in the wake of the bluff body and analysis was carried out. It was observed that by applying corner chamfer there is a decrease in turbulent wake. By increasing the chamfer, improvement in flow was observed and a smaller horseshow vortex zone was noted. Flow separation at the edges of the cylinder was noted to get delayed and reverse flow reduced due to chamfer. Introduction of chamfer effected the flow behind the cylinder significantly as well as the formation of HSV. For corner radius case, the wake region reduced till ratio of 0.4 d however, at corner radius ratio of 0.5d i.e. circular cylinder case, a growth in wake region was observed. The flow pattern for 0.1d & 0.2d radius and 0.3d & 0.4d radius showed similarity. The slope of HSV increased as corner radius increased indicating that the flow gets deflected more. As ratio of corner radius in increased, the HSV start to diminish sooner in the stream-wise direction.