Flow control downstream of a circular cylinder via a surrounding meshy cylinder in shallow water

The change of flow characteristics downstream of a circular cylinder (inner cylinder) surrounded by an outer cylinder which is constructed from screen has been investigated in shallow water for three different Froude numbers (Fr=0.25, 0.35 and 0.4) using particle image velocity technique. The diameter of the inner cylinder was kept constant during the experiments. In order to examine the effect of diameter and porosity of outer cylinder on the flow characteristics of inner cylinder, five different outer cylinder diameters (D=60mm, 70mm, 80mm, 90mm and 100mm) and four different porosity values (ß=0.4, 0.5, 0.6 and 0.7) were used. No significant effect of Froude number on the results was observed throughout the study. It was shown by the experimental results that in comparison to the bare cylinder, turbulent kinetic energy and Reynolds stresses remarkably decreased when outer meshed cylinders were placed around the cylinder. Thereby, interaction of shear layers downstream of the circular cylinder has been successfully prevented by the cited flow control method in the present investigation. The degree of weakening turbulent kinetic energy was also seen to be strongly dependent on both diameter and porosity of the outer cylinder. It was suggested by referring to the results that the outer cylinder having and should be preferred to have a better flow control downstream of a cylinder since the peak magnitude of turbulent kinetic energy was considerably low in comparison to bare cylinder and it was nearly constant for those emphasized cases..