Instability of MHD mixed convection flow of nanofluid in porous channel with thermal radiation, chemical reaction, Dufour and Soret effects

Abstract

The present paper aims to investigate a stability analysis of the mixed convection of Al2O3/water nanofluid through an anisotropic porous channel heated from below and cooled from above. The effects of the magnetic field, thermal radiation, chemical reaction, mass transfer (Soret effect) and energy transfer (Dufour effect) are taken into consideration. The equations governing the motion of the nanofluid are converted by means of hydrodynamic stability theory into a system of eigenvalue equations which is then solved numerically by the spectral collocation method. The effects of Hartmann number, thermal radiation parameter, volume fraction of nanoparticles, permeability parameter, chemical reaction parameter, Dufour and Soret number are presented and analyzed. The results showed that in presence of nanoparticles the inertia of the working fluid increases, which dampens the disturbances and thus reduces their growth. The Hartman number attenuated the amplitude of the disturbances and thus has a stabilizing effect. The permeability parameter affected the stability of the flow and its growth prevented the redistribution of disturbances within the flow, which reflected its stabilizing character. The numbers of Soret and Dufour showed an important effect on the stability of the convective mixed flow. Their growth increased the transition Reynolds number for which there was a transition to instabilities, which prevented the transition to increasingly turbulent flows. On the other hand, the increase in the chemical reaction parameter decreased the values of transition Reynolds number, thus showing that the chemical reaction maintained the instabilities.