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Instabilities in variable-property flows, and the continuous spectrum

Presented by: 
R Govindarajan [JNCASR]
Wednesday 10th September 2008 - 12:10 to 12:30
INI Seminar Room 1
Session Chair: 
J Kim
The stability work to be presented here is motivated by our ongoing numerical study of vortex merger in the presence of density-stratification. We find that very strong density stratification (even ``stable'' stratification) can (a) prevent the merger and (b) cause the vortices to break up. At low diffusivity levels the latter results from an inviscid instability due to alternately-signed density jumps packed in a known pattern. The analytical solution yields several co-existing unstable modes, and transient growth can add significantly to the linear growth at moderate times, thus speeding up the break-up of a single vortex. A related problem of Couette-Poiseuille flow and its continuous spectrum in the presence of low levels of base-flow vorticity will be discussed.
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Presentation Material: 
University of Cambridge Research Councils UK
    Clay Mathematics Institute London Mathematical Society NM Rothschild and Sons