Edge Length Effect of Bluff Bodies on Flow Structure

Abstract

This study investigates the flow structure around two identical triangles placed side by side, through experiment. Its goal is to investigate the effects of the edge length of the bluff bodies on flow structure. The flow characteristics are performed for a Reynolds number range varying from 5.000 to 10.000 under steady state conditions, and the flow was assumed to be two-dimensional. The flow characteristics around the bluff bodies were analyzed using particle image velocimetry (PIV) velocity measurement techniques, with 200 images. Water was used as the working fluid. For each case, velocity distributions along the channel height, velocity vectors and stream lines were presented to get better idea of the change of flow field. The variation in Strouhal number versus Reynolds number is presented. It was concluded for all the gap ratios that the primary recirculation zone and the secondary recirculation zone both  occurred because the interaction was not strong. Asymmetrical and unstable flow structure behind the triangles was observed during the experiments. At the point at which the fluid made the first contact with the tips of the bodies, velocity became zero. The most
effective parameters were found to be the flow velocity and the back track region. It was concluded that the points on which flow separations occurred moved away by an increasing Reynolds number. Because the vortex fields were symmetrical behind the smooth and the symmetrical elements, the Strouhal number was constant with the changing Reynolds number.