This paper examined the mechanism of both positive and negative effects of Soret‐Dufour with heat and mass transfer processes over an accelerating permeable surface. The partial differential flow equations were simplified using similarity variables, and the resulting equations were solved numerically using the spectral homotopy analysis method (SHAM). The SHAM is used in separating nonlinear equations into linear and nonlinear. The physics of each pertinent flow parameters was used to examine their influence on velocity, temperature, and concentration fields. The effect of Soret‐Dufour was examined separately, and its negative effect was used to determine its influence on velocity, temperature, and concentration fields. The result revealed that positive Soret‐Dufour enhances the boundary layer, whereas negative Soret‐Dufour parameter decreases the boundary layer. The result presented in this paper is in good agreement with existing works in literature.

ABSTRACT:The objective of this paper is to study Dufour, Soret and thermal conductivity on unsteady heat and mass transfer of magneto hydrodynamic (MHD) oscillatory flow of Jeffery fluid through a porous medium in a channel. The partial differential equations governing the flow have been solved numerically using semi-implicit finite-difference scheme with the aid of MATLAB software. The results obtained are displayed graphically and in tabular form to illustrate the effect of various parameters on the dimensionless velocity, temperature and concentration profiles, to show the effects of different parameters entering in the problem. Results from these study shows that velocity and temperature increases with the increase of Soret and Dufour why the thermal conductivity increases as temperature profile increasing. Also, it is observed that soret number increases as concentration profile decreases. © JASEM http://dx.doi.org/10.4314/jasem.v19i4.32 KEY WORDS: Heat and Mass Transfer, Dufour, Soret, Jeffery Fluid and Thermal Conductivity INTRODUCTIONThe Jeffery fluid flow with heat and mass transfer problem have many practical applications in sciences and technology. It is used in agricultural engineering to study the underground water resources, seepage of water in river-beds, food processing, magneto hydrodynamics (MHD) generators, geothermal energy extraction, electromagnetic propulsion, polymer solution and the boundary layer control in the field of aerodynamics and so on. The combined heat and mass transfer has many applications in difference branches of science and technology. The influence of heat transfer on MHD oscillatory flow of Jeffery fluid in a channel has been done by Kavita et .al. (2013). The problem was solved analytically using perturbation technique and the solution obtained shows that a rise in the chemical reaction parameter leads to reduction of the velocity as well as species concentration.

The effects of Kuvshinshiki fluid on Magnetohydrodynamic (MHD) heat and mass transfer flow over a vertical porous plate with chemical reaction of nth order and thermal conductivity was carried out. The governing partial differential equations were solved numerically using implicit Crank-Nicolson method. A parametric study was performed to illustrate the impact of visco-elastic parameter, radiation parameter, thermal conductivity parameter, magnetic parameter, Prandtl number on the velocity,temperature and concentration profiles.The results were presented graphically with tabular presentations of the skin-friction,rate of heat and mass transfer which were all computed and discussed for different values of parameters of the problem. The numerical results revealed that the visco- elastic of Kuvshinshiki fluid type is growing as concentration profile increases, while the velocity and temperature profile falls ,then the radiation and thermal conductivity were growing as velocity and temperature increases. Also Sherwood number decreases as radiation increases but Sherwood number remains unchanged as thermal conductivity growing.

This study investigated the effects of magnetic field, thermal radiation and wall slip on a Newtonian, incompressible, viscous fluid flowing through a saturated porous medium. Boundary conditions for slip at the wall hold in the fluid. The governing equations are formulated, simplified and non-dimensionalised. The dimensionless equations were solved with the help of Crank Nicolson's finite difference method. This method converges faster and it is unconditionally stable. Numerical results are presented with the aid of graph to account for the fluid parameters affecting the flow on velocity and temperature profiles.