The flow downstream of a plain cylinder with attached permeable plates having various porosity ratios was investigated experimentally using both Particle Image Velocimetry (PIV) and dye visualization techniques to control the vortex shedding around the circular cylinder. The diameter of the cylinder and length to diameter ratio of the plate were kept constant as d= 50 mm and L/d=1.0, respectively. The porosity ratio, β which can be defined as the ratio of open area to the whole body surface area was taken as β=0.4, 0.5, 0.6, 0.7 and 0.8 (permeable plates). The study was performed considering deep water flow conditions and depth-averaged free stream velocity was taken constant as U = 95.2mm/s which corresponded to a Reynolds number of Re_d = 5000 based on the cylinder diameter. The results of a plain cylinder were compared with the results of cylinder with permeable plates in order to understand the control effect. Both qualitative and quantitative results revealed that the plates are effective on the unsteady flow structure downstream of the cylinder, i.e. the vortex formation length was increased, turbulent statistics was reduced and both width and length of the wake were changed by usage of permeable plates attached around the separation point of the cylinder.
展开▼
