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Effect of Thermal / Gravity Modulation on the Onset of Rayleigh-Benard Convection in a Couple Stress Fluid
M.S. Malashetty and D. Basavaraja

The stability of a Boussinesq couple stress horizontal fluid layer, when the boundaries are subjected to time periodic temperature modulation or in the presence of time periodic body force, is analyzed using linear theory. A perturbation method is adopted in arriving at the critical Rayleigh number and the critical wave number for small amplitudes of the temperature modulation or gravity modulation. The stability of the system characterized by a correction Rayleigh number is calculated as a function of the Prandtl number, couple stress parameter and the frequency of modulation. We have shown that it is possible to advance or delay the onset of convection by time periodic temperature modulation and to advance by time periodic body force. It is found that the couples stress parameter has a significant effect on the stability of the system. The influence of Prandtl number on the stability of the system is brought out.

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