THE HORSESHOE VORTEX AND LEE WAKE VORTICES AROUND A VERTICAL CIRCULAR CYLINDER IN OSCILLATORY FLOW

Abstract

This paper has presented the results of numerical and experimental investigations on the flow fields around the base of a vertical circular cylinder subjected to the oscillatory flow. The calculated results from the three-dimensional unsteady Navier-Stokes equation have shown that the development of horseshoe vortex and lee-wake vortices governed by the Keulegan-Carpenter number agree reasonably well with those measured by Particle Image Velocimetory (PIV). Detailed analysis of numerical simulations has indicated that the horseshoe vortex exhibits a unique flow pattern which is different from the vortex topology in steady flow fields. The characteristics of lee-wake vortices near the bed and the bed shear stress beneath those vortices have been investigated in detail.