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Effects of Prandtl number and a new instability mode in a plane thermal plume

Published online by Cambridge University Press:  14 November 2007

R. LAKKARAJU  and
MEHEBOOB ALAM
R. LAKKARAJU
Affiliation:
Engineering Mechanics Unit, Jawaharlal Nehru Center for Advanced Scientific Research, Jakkur PO, Bangalore 560064, India
MEHEBOOB ALAM*
Affiliation:
Engineering Mechanics Unit, Jawaharlal Nehru Center for Advanced Scientific Research, Jakkur PO, Bangalore 560064, India
*
†Author to whom correspondence should be addressed: meheboob@jncasr.ac.in
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Abstract

The effect of Prandtl number on the linear stability of a plane thermal plume is analysed under quasi-parallel approximation. At large Prandtl numbers (Pr > 100), we found that there is an additional unstable loop whose size increases with increasing Pr. The origin of this new instability mode is shown to be tied to the coupling of the momentum and thermal perturbation equations. Analyses of the perturbation kinetic energy and thermal energy suggest that the buoyancy force is the main source of perturbation energy at high Prandtl numbers that drives this instability.

Type
Papers
Information
Journal of Fluid Mechanics , Volume 592 , 10 December 2007 , pp. 221 - 231
Copyright
Copyright © Cambridge University Press 2007

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