Dual Solutions for Homogeneous-Heterogeneous Reactions on Stagnation Point Flow Over a Stretching/Shrinking Sheet in a Non-Darcy Porous Medium Saturated with a Nanofluid

The effects of a homogeneous-heterogeneous reactions on stagnation point flow over a stretching/shrinking sheet in a non-Darcy porous medium are numerically investigated in this paper. The model used for the nanofluid incorporates the effects of the volume fraction parameter. Two types of nanofluids, titanium oxide-water and gold-water nanofluids are used in this study. The model developed by Chaudhary and Merkin for homogeneous-heterogeneous reaction in boundary layer flow with equal diffusivities for reactant and autocatalyst is used in this study. The basic boundary layer partial differential equations of motion and concentration are reduced to a set of non-linear ordinary differential equations, that are numerically solved using the Matlab bvp4c package. A comparison is made with results available in the literature and found to be in good agreement. A dual solution obtained for some special case when stretching/shrinking parameter less than –1. The behaviour of the dual solution on velocity, concentration and skin friction are analyzed with other effective parameters as permeability parameter, Schmidt number, strength of homogeneous and heterogeneous reaction. The momentum boundary layer thickness increases in the case of first solution while an opposite phenomena observed for the second solution. The concentration boundary layer thickness increases with Darcy number while decreases with the strength of the homogeneous reaction.