Unsteadiness and control by using thermal boundary modulation in restricted fluid domain of vertical Bridgman apparatus

The behaviour of heat and mass transfer in a square vertical Bridgman cavity containing a low Prandtl number fluid and subjected to oscillatory heating is investigated with respect to the flow instability and transition from steady to unsteady regimes for fluid isothermally heated from below. Effects of thermal modulation on the all regimes occurring in the cavity when increasing the convection intensity are analysed. To focus on the control by using the modulation, two cases are distinguished according to the initial state of the melt flow, steady or time dependent. The steady regime exhibits the existence of a characteristic modulation frequency allowing the reduction of the average intensity of the flow. For the range of the unsteady flows considered in this study, the existence of a critical modulation frequency allowing the control of the amplitude of the oscillating heat and flow, has been identified.