Flow control behind a circular cylinder via a porous cylinder in deep water

Abstract

Abstract. In this present work, the effects of surrounding outer porous cylinder on vortex structure downstream of a circular inner cylinder are investigated experimentally in deep water flow. The porosity of outer cylinder were selected as β = 0. 4, 0.5, 0.6, 0.65, 0.7, 0.75, 0.8 and 0.85. Porosity is defined as the ratio of the gap area on the body to the whole body surface area. The ratio of outer cylinder diameter to inner cylinder diameter, D o /D i was selected as 2.0, i.e. the inner cylinder diameter is D i = 30 mm where the outer cylinder diameter is D o = 60 mm. All experiments were carried out above a platform. The water height between the base of the platform and the free surface was adjusted as 340 mm. Free stream velocity is U = 156 mm/s, which corresponds to the Reynolds number of Re i = 5,000 based on the inner cylinder diameter. It has been observed that the outer porous cylinders have influence on the attenuation of vortex shedding in the wake region for all porosities. The turbulent intensity of the flow is reduced at least 45% by the presence of outer porous cylinder compared to the bare cylinder case. The porosities β = 0.4 and 0.5 are most suitable cases to control the flow downstream of the circular cylinder.

Passive Flow Control for Drag Reduction on a Cylinder in Cross-Flow Using Leeward Partial Porous Coatings

“…This resulted in an approximate relative error e a =| ( f 1 − f 2 )/( f 1 ) |= 3.98% and a fine-grid convergence in-dex GCI f ine = (1.25e a )/(r p − 1) = 1.36%. The apparent order p is defined according to Equation (13), where q(p) = 0 in this case as r is constant, 32…”

“…There is good agreement on the impact of a full porous coating on the wake of a cylinder, with the wake being stabilised due to the reduction or the delay of vortex shedding [2,[9][10][11][12][13][14][15][16][17][18][19]. Consequently, many studies concluded that the porous coating reduced the fluctuation of aerodynamic forces [2,9,10,[17][18][19].…”

Control of cylinder wake flow and noise through a downstream porous treatment

“…Gozemen [21] suppressed vortex shedding from a circular cylinder by using a porous coating in deep water, showing that the turbulent intensity of the flow downstream the porous cylinder was much smaller than the rigid solid cylinder. Sueki et al [22] cylinder with a diameter of D=25mm.…”

Experimental-laboratory study of the flow around mussel shocks

“…This technique was recently used successfully by [13] who studied experimentally the effects of surrounding outer porous cylinder on vortex structure downstream of a circular inner cylinder in deep water flow. Furthermore, PIV experiments were conducted by [14] and also included in the recent research by [15].…”