Flow control in the wake of a circular cylinder by means of perforated semi circular cylinder and splitter plate

The main purpose of the present experimental study was to control unsteady flow behaviors in the wake region of a circular cylinder (inner cylinder) by means of permeable semi circular cylinder (outer cylinder) and splitter plate. Inner and outer cylinder diameters and Reynolds number with respect to inner cylinder diameter were kept constant as 50 mm, 125 mm and Re=5000 respectively throughout the experiments. Two different porosity ratios were designated as cylinder porosity ratio (βC) and plate porosity ratio (βP). Three different cylinder porosity ratio and four different plate porosity ratio were determined as βC=0.3, 0.5, 0.7 and βP=0, 0.3, 0.5, 0.7 respectively. Also, plate angle (α) relative to the flow direction was defined to investigate the effect of splitter plate location to the flow behavior. And these plate angles were chosen as α=90°, 120°, 150°, 180°. For all configurations, dye visualization method was utilized initially, and then to have quantitative results PIV technique was applied. Results indicated that as the plate porosity ascends the TKEmax values has diminishing trend. Also cylinder porosity has remarkable influence on TKEmax values, TKEmax reduction was obtained for lower porous cylinders. And plate angles of 150° and 180° were found to be the most effective angles regardless of the plate porosity ratio. The highest TKEmax decrease was attained as 34% for the βC=0.3, βP=0.5 at 180°. On the other hand, βC=0.7 has insignificant control over flow by reason of its high permeability. Consequently, βC=0.3 and 0.5, βP=0.5 and 0.7, and plate angles of 150° and 180° were found as the most effective parameters in order to control the flow.