Double-diffusive convection from a permeable vertical surface under convective boundary condition

The objective of the present study is to investigate the simultaneous effects of thermal and concentration diffusions on a mixed convection boundary layer flow over a permeable surface under convective surface boundary condition. Using the local similarity method, it has been shown that a set of suitable similarity transformations reduce the non-linear coupled partial differential equations governing the flow, thermal and concentration fields into a set of non-linear coupled ordinary differential equations. Next, two point boundary value problem for non-linear coupled ordinary differential equations have been solved numerically using an implicit finite difference scheme in combination with the quasi-linearization technique. It is interesting to note that dual solutions exist for buoyancy assisting flow, besides that usually reported in literature for buoyancy opposing flow. Further, the buoyancy assisting force causes considerable overshoot in the velocity profile. Prandtl and Schmidt numbers strongly affect the thermal and concentration boundary layer thicknesses, respectively. (C) 2011 Elsevier Ltd. All rights reserved.