Nonlinear stability analysis of double diffusive convection in a fluid saturated porous layer with variable gravity and throughflow

Abstract

This paper develops a detailed study of linear and nonlinear stability analyses, for the double diffusive convection problem in a porous medium, when heating is done from below and, salting is done from below as well as from above. The linear analysis is performed using normal mode technique and nonlinear analysis is developed using energy technique. The Chebyshev pseudo-spectral technique is performed to analyze the effect of variable gravity field and throughflow on the behavior of system stability. The results obtained from linear and nonlinear analysis are compared and found that the results are in better agreement for the heated from below and salted from above system however, the comparatively less agreement is obtained for the system when both heating and salting are done from below. The direction of throughflow and gravity field have considerable effect on the stability of system. The behavior of gravity field is invariant for both the type of system heating and salting from below as well as heating from below and salting from above. The solute Rayleigh number stabilizes the system for heating from below and salting from below, however, destabilizes the system for heating from below and salting from above. In the absence of gravity field, a comparatively good agreement between thresholds is seen for Q = 0, however, the agreement is shifted towards positive value of Q or negative value of Q when gravity is found to be present in the system. Thus, effect of gravity field is dominant on the influences of throughflow on the stability of system.