DYNAMICS OF RIPPLE BED VORTICES

This paper presents the results of an experimental investigation into the dynamics of vortices formed by and shed from ripples under oscilla tory motion. Particle Image Velocimetry (PIV) was used to acquire deta iled velocity measurements at several phases of oscillation for each o f four flow conditions: three purely horizontal oscillations and a 're al' wave with a vertical velocity component. For each of the flows, th e vortices were located in the flow maps and defined at each time-step by their circulations and sizes. These calculated characteristics wer e compared with the predictions from a discrete-vortex model (DVM) dev eloped at the University of Wales, Banger.