EFFECT OF TEMPERATURE MODULATION ON RAYLEIGH-B??NARD CONVECTION IN A ROTATING LAYER OF A FERROMAGNETIC FLUID

EFFECT OF TEMPERATURE MODULATION ON RAYLEIGH-B??NARD CONVECTION IN A ROTATING LAYER OF A FERROMAGNETIC FLUID

The stability of a rotating horizontal layer of ferromagnetic fluid heated from below is examined when, in addition to a steady temperature difference between the walls of the layer, a time-dependent sinusoidal perturbation is applied to the wall temperatures. Only infinitesimal disturbances are considered. The effects of the oscillating temperature field are treated by a perturbation expansion in powers of the amplitude of the applied field. The onset criterion is derived when the condition for the principle of exchange of stabilities is valid. The shift in the critical Rayleigh number is calculated as a function of the frequency of modulation, magnetic parameters, Taylor number and Prandtl number. The effect of various parameters is found to be significant for moderate values of the frequency of modulation. It is shown that, when the thermal excitation is symmetric, supercritical motion is more pronounced for low Prandtl number ferro fluids. Further, for the case in which only the bottom wall temperature is modulated, the effect of rotation is to stabilize the system at low frequencies and the opposite is true for moderately large frequencies. The problem throws light on external means of controlling convection in ferromagnetic fluid applications.

VENKATESH MURTHY RASHMI

Mathematics