Effect of topographic features on surface, interfacial and internal gravity waves
Orateur : Anirban Guha, University of Dundee, UK
Abstract : The first part of this talk will focus on surface and interfacial gravity wave interactions with rippled-bottom - the well known "Bragg resonance". While classical theory used for developing surface/interfacial wave triads, and more importantly, their numerical implementation using the Higher Order Spectral method, assumes irrotational flow, it will be shown that such stiff requirements can be slightly relaxed - piecewise constant vorticity in multi-layered setting (each layer of constant density and vorticity) is amenable to the same theoretical and numerical schemes. Velocity shear strongly influences the resonance conditions since, in addition to changing the intrinsic frequencies, it can cause unequal Doppler shifts between the surface, pycnocline (interface), and the bottom.
The second part of the talk will be a short discussion on the effect of classic Bragg resonance (surface wave - topography interactions) on Stokes’ drift, a key mechanism for tracer transport in oceans. It will be shown that a patch of bottom ripple acts as a non-surface-invasive particle trap, and thus can have applications in ocean pollution mitigation.
The third part of the talk will focus on the energy exchange in resonant and near-resonant triads consisting of weakly nonlinear internal gravity wave packets in a bounded domain in the presence of a slowly varying topography. The effect of variation of the wavenumbers on the horizontal and vertical wavenumber condition given by k1 + k2 + k3 = 0 will be discussed as the waves constituting the resonant triads interact in region of a varying domain height in uniform and non-uniform stratification. Moreover, the effect of the shape of the topography (quantities such as (dh/dx)2 and d2h/dx2, where h is the topography) in the interaction of three waves will be discussed.
Date et lieu : le vendredi 10 avril à 11h00, salle de séminaires IRPHE
Voir en ligne : la page personnelle de l’orateur