ONSET OF MANIFEST CONVECTION IN A LAYER OF FLUID WITH A TIME-DEPENDENT SURFACE TEMPERATURE

Experiments have been performed in deep layers of fluid in which the bottom surface temperature was increased at a constant rate. It was found that when the thermal boundary layer was only a small fraction of the total depth of the fluid layer, the onset of manifest convection was independent of the layer depth. The predictions of linear time-dependent theory that the time of onset of manifest convection should vary with the - 2/5 power of the rate of bottom surface temperature increase and that the horizontal spacing of the convection cells should vary with the -1/5 power of the rate of bottom surface temperature increase were verified within reasonable limits.