Reduction in drag and vortex-induced vibration of a circular cylinder covered by a porous layer in the laminar regime

Abstract

The reduction in drag and vortex-induced vibration (VIV) of a circular cylinder covered by a porous layer is numerically studied in the laminar regime. The mass ratio and damping ratio of the system are fixed at mr = 2 and ξ = 0.01, respectively. The effects of the Darcy number (Da = 10−4, 10−3 and 10−2), the relative layer thickness (b = 0.25, 0.5 and 1), the Reynolds number (Re = 100, 150 and 200), and reduced velocity (2 ≤ Ur ≤ 10) on the vortex shedding pattern, vibration amplitude, and dynamic forces on the system are investigated. Both the one and two degrees of freedom of motion are considered. Results show that the porous layer with Da = 10−2 is effective in drag reduction and VIV suppression for various Reynolds numbers. A porous layer with Da = 10−3 could also suppress VIV while enlarging the drag force on the system.