Double Diffusive Flows over a Stretching Sheet of Variable Thickness with or without Surface Mass Transfer

This paper presents a numerical investigation of the steady two-dimensional mixed convection flow along a vertical semi-infinite stretching sheet of variable thickness. The effect of double diffusion on velocity, thermal and concentration fields in presence of power-law temperature and concentration distributions at wall along with surface mass transfer is considered. The nonlinear coupled partial differential equations governing the flow, thermal and concentration fields are first transformed into a nondimensional set of coupled nonlinear partial differential equations and solved numerically using an implicit finite-difference scheme in combination with the Newton's linearization technique to obtain nonsimilar solutions at each stream-wise location. Numerical results are presented to discuss the effects of various physical parameters on the velocity, temperature, and concentration fields. Furthermore, the numerical results for the local skin friction coefficient, local Nusselt number, and local Sherwood number are also reported. For a fixed buoyancy force, the skin friction coefficient and Nusselt number increase with Prandtl number. The increase in the Prandtl number causes about a 30% reduction in the thickness of the thermal boundary layer. The wall thickness parameter enhances the thickness of the momentum boundary layer and the velocity overshoot is observed up to 20% for wall thickness parameter α = 0.9. In contrast, the increase of power-law index parameter m from m = 0.5 to m = 1.5 reduces approximately 10% to 25% the momentum and thermal boundary layer thicknesses depending on the values of other parameters.