Thursday 24 Oct 2013Critical layer and radiative instabilities in shallow water

Xavier Riedinger - University of Exeter

Harrison 101 15:00-16:00

In this presentation we present the mechanisms of critical layer instability and radiative instability in shallow water.
Modifying a boundary layer shear profile from piecewise to continuous we show that critical layer instability is related
to a resonance instability between a a normal mode and a quasi-mode (eigenmode not obtained on the real path).
Using a shooting code and a pseudo-spectral code on a path in the complex plain we obtain the characteristics of the modes.
Using asymptotic matching we get the similar mechanism for the two instabilities as an overreflexion process
associated to a bounded cavity. We show how to obtain growth rates and how the two instabilities interact.

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