Stability analysis of mixed convection in a porous horizontal channel filled with a Newtonian Al2O3/Water nanofluid in presence of magnetic field and thermal radiation

Abstract

• Stability analysis of mixed convection of Newtonian nanofluid in porous media. • Magnetic field and thermal radiation are taken into consideration in the problem. • Prandtl, and Richardson numbers maintain instabilities in convective flow . • Magnetic field, thermal radiation and medium's permeability stabilize the flow. • Nanoparticles into the base fluid increases the inertia of the fluid. This paper investigates a stability analysis of mixed convection of A l 2 O 3 / W a t e r nanofluid in a horizontal porous channel heated from below and cooled from above. Certain effects such as magnetic field and thermal radiation are taken into consideration. The permeability of the porous medium is described by Darcy's model. Starting from the Navier-Stokes equations to which the energy and Maxwell equations are coupled and under the assumption of an analysis in normal mode, a system of differential equations with eigenvalues governing the stability of the flow is derived and solved numerically by the spectral collocation method. The effects of the magnetic field, thermal radiation, volume fraction of nanoparticles, permeability of the medium and many other important parameters are presented and analyzed. The results show that the introduction of the nanoparticles into the base fluid increases the inertia of the fluid, which dampens the disturbances. Among the different geometric shapes of nanoparticles, the blade shape has a more stabilizing effect on the stability of the convective flow. It is also shown that oxide-type nanoparticles have a more stabilizing effect compared to metallic-type nanoparticles on small wave number disturbances. In the case of large wave numbers, the opposite is observed. Parameters such as Prandtl number and Richardson number maintain instabilities in convective flow. On the other hand, the magnetic field, the thermal radiation and the permeability of the porous medium affect the stability of the convective flow and all have stabilizing effects, which makes it possible to control the mixed convection of nanofluid.