The effects of perforated cylinders on the vortex shedding on the suppression of a circular cylinder

DANTEC DYNAMICS GmbH;LAVISION;MIT s.r.o.;TSI GmbH11th International Conference on Experimental Fluid Mechanics, EFM 2016 --15 November 2016 through 18 November 2016 -- --The aim of this study is the control of unsteady vortical flow occurred downstream of a circular cylinder located in shallow water flow using concentrically located outer perforated cylinder. The porosities, ß have been changed between 0.1 and 0.8 in the present study. The increments of porosity ß were taken as 0.05 in the range of 0.1 and 0.8 with a hole diameter of d=10 mm. The ratio of inner cylinder diameter to outer cylinder diameter, Di/Do was selected as 0.25, 0.3, 0.4, 0.5 and 0.6 the inner cylinder diameter is Di=50mm where the outer cylinder diameter is Dd=100mm. Experiments were performed at a constant depth of the water level as h=50mm (half of the outer cylinder diameter). Free stream velocity was taken as U=100 mm/s corresponding to a Reynolds number of Re Do=10000 based on the outer cylinder diameter. It has been observed that the inner circular cylinder was highly affected by the existence of surrounding outer perforated cylinders. It is observed that the intensity of Reynolds shear stress correlating, is completely attenuated in the region both downstream of concentric cylinder and between the concentric cylinders. It is determined from the experiments that porosity, ß =0.55 is the most effective parameter for control of flow structure that is occurred from the inner cylinder. © The Authors, published by EDP Sciences, 2017