In the present study, it was aimed to suppress the vortex shedding occurred in the near wake of a circular cylinder (inner cylinder) by perforated cylinder (outer cylinder) in shallow water flow. The inner cylinder (Di) and outer cylinder (Do) have fixed diameters, such as Di = 50 mm and Do = 100 mm, respectively. The effect of porosity, β, was examined using four different porosity ratios, 0.3, 0.5, 0.6 and 0.8. In order to investigate the effect of arc angle of outer cylinder, α, four different arc angles, α = 360°, 180°, 150° and 120° were used. The experiments were implemented in a recirculating water channel using the particle image velocimetry, PIV technique. The depth-averaged free-stream velocity was kept constant as U∞ = 100 mm/s which corresponded to a Reynolds number of Re = 5000 based on the inner cylinder diameter. The results demonstrated that the suppression of vortex shedding is substantially achieved by perforated outer cylinder for arc angle of α = 360° at β = 0.6. Turbulence Kinetic Energy statistics show that porosity, β, is highly effective on the flow structure. In comparison with the values obtained from the case of the bare cylinder, at porosity β = 0.6, turbulence characteristics are reduced by %80. Also, the point, which the values of maximum TKE, shift to a farther downstream compared to the case of bare cylinder.
Reduction of Cd in circular cylinder using three passive control at Re=500
