Global stability for convection induced by absorption of radiation.

Abstract

We study the linear instability and nonlinear stability of a model, for convection induced by selective absorption of radiation, due to Krishnamurti. The nonlinear analysis yields critical Rayleigh numbers very close to the critical ones of linear instability theory and this demonstrates that linear theory effectively captures the physics of the onset of convection. Realistic boundary conditions appropriate to fixed surfaces are analysed and these reflect the experiments performed by Krishnamurti. The results obtained here lend much credence to use of the model of Krishnamurti for convection in a fluid layer stably stratified when the heat source depends on the concentration of the stratifying agent.