Stratified shear flow instabilities in the non-Boussinesq regime

E. Heifetz, Julian Mak

Research output: Contribution to journalArticlepeer-review

Abstract

Effects of the baroclinic torque on wave propagation normally neglected under the Boussinesq approximation is investigated here, with a special focus on the associated consequences for the mechanistic interpretation of shear instability arising from the interaction between a pair of vorticity-propagating waves. To illustrate and elucidate the physical effects that modify wave propagation, we consider three examples of increasing complexity: wave propagation supported by a uniform background flow; wave propagation supported on a piecewise-linear basic state possessing one jump; and an instability problem of a piecewise-linear basic state possessing two jumps, which supports the possibility of shear instability. We find that the non-Boussinesq effects introduce a preference for the direction of wave propagation that depends on the sign of the shear in the region where waves are supported. This in turn affects phase-locking of waves that is crucial for the mechanistic interpretation for shear instability, and is seen here to have an inherent tendency for stabilisation.
Original languageEnglish
Article number086601
Number of pages15
JournalPhysics of Fluids
Volume27
Early online date19 Aug 2015
DOIs
Publication statusPublished - Aug 2015

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