Summary. The linear and non-linear stability of double diffusive convection in a sparsely packed porous layer is studied using the Brinkman model. In the case of linear theory conditions for both simple and Hopf bifurcations are obtained. It is found that Hopf bifurcation always occurs at a lower value of the Rayleigh number than one obtained for simple bifurcation and noted that an increase in the value of viscosity ratio is to delay the onset of convection. Non-linear theory is studied in terms of a simplified model, which is exact to second order in the amplitude of the motion, and also using modified perturbation theory with the help of self-adjoint operator technique. It is observed that steady solutions may be either subcritical or supercritical depending on the choice of physical parameters. Nusselt numbers are calculated for various values of physical parameters and representative streamlines, isotherms and isohalines are presented.
The investigation of Non-Darcian Benard Marangoni Convection (NDBMC) is carried out in a Superposed Fluid-Porous (SFP) layer, which consists of an incompressible, sparsely packed single component fluid saturated porous layer above which lies a layer of the same fluid, with temperature dependent heat sources in both the layers. The upper surface of the SFP layer is free with Marangoni effects depending on Temperature, where the lower surface of the SFP layer is rigid. The thermal Marangoni numbers are obtained in closed form for two sets of thermal boundaries set (i) Adiabatic-Adiabatic and set (ii) Adiabatic-Isothermal. Influence of temperature dependent heat source in terms of internal Rayleigh numbers, viscosity ratio, Darcy Number, thermal diffusivity ratio on NDBMC, is investigated in detail.
The effect of Soret parameter on double diffusive Marangoni convection in a two-layer system, comprising an incompressible two component fluid saturated porous layer over which lies a layer of the same fluid under micro gravity condition is investigated analytically. The upper boundary of the fluid layer is free, the lower boundary of the porous layer is rigid and both the boundaries are insulating to heat and mass. At the interface, the velocity, shear stress, normal stress, heat, heat flux, mass and mass flux are assumed to be continuous. Thermal Marangoni number is obtained by solving ordinary differential equations using method of exact solution. The effect of different physical parameters on double diffusive Marangoni convection are also investigated in detail.
The problem of triple diffusive Marangoni convection is investigated in a composite layer comprising an incompressible three component fluid saturated, sparsely packed porous layer over which lies a layer of the same fluid. The lower rigid surface of the porous layer and the upper free surface are considered to be insulating to temperature, insulating to both salute concentration perturbations. At the upper free surface, the surface tension effects depending on temperature and salinities are considered. At the interface, the normal and tangential components of velocity, heat and heat flux, mass and mass flux are assumed to be continuous. The resulting eigenvalue problem is solved exactly for linear, parabolic and inverted parabolic temperature profiles and analytical expressions of the thermal Marangoni number are obtained. The effects of variation of different physical parameters on the thermal Marangoni numbers for the profiles are compared.
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