EXPERIMENTAL INVESTIGATION OF FLOW STRUCTURE DOWNSTREAM OF PERMEABLE CYLINDERS

Abstract

Flow structure downstream of permeable cylinders was investigated using high-image density Particle ImageVelocimetry technique in deep water. The free stream velocity is U∞= 156 mm/s, which corresponds to the Reynoldsnumber of Re=6250 based on the cylinder diameter D=37.5 mm. To reveal the effect of the porosity, four differentporosities (β= 0.4, 0.5, 0.6 and 0.7) were used. This study showed that the usage of permeable cylinder decreases theoccurrence of large-scale vortical structures downstream of the bluff body. As the porosity increases, turbulent kineticenergy, Reynolds shear stress and intensity of turbulences decrease as a sign of attenuated fluctuations in the wakeregion. For the permeable cylinders having the porosity higher than 0.6, the flow behaves as there is no object in flow.