Graduate Student Seminar | Subasha Wickramarachchi, Evolution of the vorticity and flow field generated by oscillatory flows over ripples at a quasi-steady state

MC 5417

Speaker

Subasha Wickramarachchi
Department of Applied Mathematics, University of Waterloo

Title

Evolution of the vorticity and flow field generated by oscillatory flows over ripples at a quasi-steady state

Abstract

In this talk, I extend the previous talk by considering much longer time periods when the flow attains a quasi-steady state. During the quasi-steady state, the vortices generated remain close to the ripple and dissipate before reaching much higher for all cases except the all-symmetric case. For the asymmetric ripple and the asymmetric forcings, a consistent negative mean flow can be observed, which tends to attain a near-steady speed after about 35 cycles. Furthermore, vortex interactions with the ripple contribute a substantial amount of momentum flux to the system, as do the strong shear layers that can be seen to form at a short distance on either side of the ripple crest. The newly generated vortex pairs exhibit initial trajectories in the direction of the mean flow and are found to trace the transfer of momentum from near the ripple to area of mean current.