Onset of Convection in a Layer of Water Formed by Melting Ice from Below

The onset of convection, or the critical Rayleigh number in a layer of water formed continuously by melting ice from below, has been determined experimentally. Homogeneous, bubble-free ice was prepared, and used in all the experiments. The critical Rayleigh number Rac for a fluid undergoing phase change and density inversion is not a single value but may be correlated empirically as a function of warm plate temperature T8 by Rac = 14 200 exp (−6.64 × 10−2T8). This relation is valid for T8 varying from 6.72-25.50°C. The initial ice sample temperature T0 was varied from −4.8 to −22.00°C. The effect of T0 was found to be insignificant.