Viscous Forces Acting on Oscillating Flat Plate and Circular Cylinder in Steady Flow

Abstract

Viscous hydrodynamic forces acting on an oscillating circular cylinder and an oscillating flat plate in steady flow are experimentally investigated. The steady-drag, oscillating-drag, added-mass and lift coefficients obtained from measured forces show significant effects of the oscillating flow and the steady flow. The simulation results by a discrete vortex method demonstrate that it is partly because the separated vortices grow much bigger than those for a purely oscillation mode, and that a modified Keulegan-Carpenter number based on the relative displacement of the fluid governs the flow field around an oscillating cylinder in steady flow, The experimental results also show that the increase or the relative velocity on the cylinder surface due to the added steady flow causes the increase of the drag coefficients, and that the time history effect due to the separated vortices generated in previous cycles is significant particularly at low modified K_c number.