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Onset of Convection in a Horizontal Porous Layer Saturated with Reacting Fluid
M.S. Malashetty and S.N. Gaikwad

The interaction of exothermic chemical reaction and the natural convection in a horizontal sparsely packed inert porous layer cooled from the top boundary with two different bottom thermal boundary conditions namely, isothermal and adiabatic, and with fluid viscosity different from the effective viscosity is investigated. A linear stability analysis was used to analyze the stability of the base state solution with respect to convective perturbations and the resulting eigenvalue problem is solved approximately, based on a single-term Galerkin method. The critical Rayleigh number and its cor-responding wave number are obtained for different values of the Frank–Kamenetskii number FK, porous parameter s and the viscosity ratio Kr. It is found that there is a critical value of Frank–Kamenetskii number FK = (FK)c at which the system is most unstable. It is also found that the viscosity ratio delays the onset of convection. It is found that, with chemical reactions, the fluid in the porous medium is more prone to instability as compared to the case in which chemical reactions are absent.

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