Explosive instability due to flow over a rippled bottom

Anirban Guha (Lead / Corresponding author), Raunak Raj

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Abstract

In this paper, we study Bragg resonance, i.e., the triad interaction between surface and/or interfacial waves with a bottom ripple, in the presence of background velocity. We show that when one of the constituent waves of the triad has negative energy, the amplitudes of all the waves grow exponentially. This is very different from classic Bragg resonance in which one wave decays to cause the growth of the other. The instabilities we observe are "explosive" and are different from normal mode shear instabilities since our velocity profiles are linearly stable. Our work may explain the existence of large-Amplitude internal waves over periodic bottom ripples in the presence of tidal flow observed in oceans and estuaries.

Original languageEnglish
Pages (from-to)283-290
Number of pages8
JournalNonlinear Processes in Geophysics
Volume26
Issue number3
Early online date21 Aug 2019
DOIs
Publication statusPublished - 2019

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