Long internal waves in shear flows: topographic resonance and wave-inducedglobal instability

Issues pertaining to a mechanism whereby long internal waves in shallow sea s may give rise to enhanced rates of resuspension of sedimentary material a re addressed. The proposed mechanism is intimately related to the creation of conditions in the bottom boundary layer which are favorable for how sepa ration and spontaneous onset of global instability. It is shown that long w aves generated by topographic resonance and propagating upstream against th e oncoming current, especially a sheared current, have a strong tendency to release a coherent, pulsating dynamics in their footprint. The passage-thr ough-resonance problem For a sheared, stratified Row is considered, conditi ons for topographic resonance in the Row model are defined, and preliminary results for the unsteady dynamics in the boundary layer under the footprin t of a long wave packet are presented. (C) 2001 Elsevier Science B.V. All r ights reserved.