Analysis on the onset of microwave induced convection within a horizontal water layer

Abstract

This work is concerned with the onset of convection due to microwave incidence in a horizontal water layer. The onset characteristics in terms of critical Rayleigh (Rac) and wave (kc) numbers have been determined for various regimes of microwave heating, namely thin, sinusoidal and thick samples. It has been shown that both Rac and kc exhibit oscillatory patterns in sinusoidal regimes of microwave heating, while they attain asymptotes in thin and thick sample regimes. The variation patterns of critical Rayleigh and wave numbers from thin to thick samples have been correlated with the degree of asymmetry in internal heat source profiles. The analysis is carried out over the entire spectrum of microwave source configurations. It has been shown that there exists a one-to-one correlation between the variation patterns of Rac and kc with the degree of symmetry in internal heat source profiles. The total power required to initiate the convection has also been analysed in terms of the modified Rayleigh number .