Positive and negative soret and dufour mechanism on unsteady heat and mass transfer flow in the presence of viscous dissipation, thermal and mass buoyancy

The combined effects of positive and negative Soret and Dufour on unsteady heat and mass transfer flow in the presence of viscous dissipation, thermal and mass buoyancy is considered. The governing boundary layer equations are formulated to be coupled, nonlinear partial differential equations and are non-dimensionalised. A robust, efficient and accurate spectral relaxation method is used to solve the dimensionless, unsteady, nonlinear and coupled partial differential equations. All pertinent flow parameters are analysed and presented graphically. The effect of flow parameters on the physical quantities of engineering interest is also tabulated. It was found out that the negative Soret reversed the concentration profile while negative Dufour reversed the temperature profile. The present results are compared with previous works and were found to be in good agreement.