International Journal of Modern Embedded System (IJMES) ISSN: 2320-9003(Online) Volume 3, Issue 3, November, 2015 RES Publication © 2012 Page | 28 http://ijmes.info Effect of Porous Medium on Unsteady Heat & Mass Transfer Flow of Fluid P.Biswas1 st Mathematics Discipline Khulna University Khulna-9208 pronabbiswas16@gmail.com M.K.Das2 nd Mathematics Discipline Khulna University Khulna-9208 mahadeb.ku@gmail.com A.islam3 rd Mathematics Discipline Khulna University Khulna-9208 is_arif@yahoo.com Abstract: The effect of porous medium on unsteady heat and mass transfer flow of fluid in a porous medium and non-porous medium is investigated. The problem is governed by coupled non-linear partial differential equations. The dimensionless equations of the problem have been solved numerically by using explicit finite difference method. The effect of flow parameters on the velocity field, temperature field and concentration field are discussed quantitatively and the obtained solutions are shown graphically. Keywords: Heat and Mass Transfer, MHD, Porous Medium, Non-porous medium, explicit finite difference method. I. INTRODUCTION The phenomenon of heat and mass transfer has been the object of extensive research due to its science and technology. Magneto hydrodynamic (MHD) is currently undergoing a period of great enlargement and differentiation of subject matter. The MHD heat and mass transfer processes are of interest in power engineering, metallurgy, astrophysics, and geophysics. Unsteady convective flows in a porous medium have received much attention in recent time due to its wide applications in geothermal and oil reservoir engineering as well as other geophysical and astrophysical studies. [1]The unsteady fluid flow past a moving plate in the presence of free convection and radiation were studied by Cogley et. al. (1968),[2] Das, Deka and Rang Soundarker (1996),[3] Abdus Satter and Hamid Kalim et. al.(1996), [4] Grief et. al.(1971), [5] Ganeasan and Loganathan (2002). All these studies have been confined to unsteady flow in a nonporous medium. From the previous literature survey about unsteady fluid flow, we observe that little papers were done in porous media. The effect of radiation on MHD flow and heat transfer must be considered when high temperatures are reached. [6] Cookey et. al. (2003), researched the influence of viscous dissipation and radiation on unsteady MHO free-convection flow past on infinite heated vertical plate in a porous medium with time dependent suction. [7] E. I. Naby et. al. (2004), studied unsteady MHD convective heat transfer past a semi- infinite vertical porous moving plate. [8] Anwar et. al. (2009), studied and combined the effects of Soret and Dufour diffusion and porous impedance on laminar magneto- hydrodynamic mixed convection heat and mass transfer of an electrically-conducting, Newtonian, Boussinesq fluid from a vertical stretching surface in a Darcian, porous medium under uniform transverse magnetic field. Heat and mass transfer for Soret and Dufour's effect on mixed convection boundary layer flow over a stretching vertical surface in a porous medium filled with a visco-elastic fluid in the presence of magnetic field. [9] N. Ahmed and H. Kalita et. al. (2012) is examined and investigates the problem of an oscillatory MHD free convective flow through a porous medium with mass transfer, soret effect and chemical reaction when the temperature as well as concentration at the plate varies periodically with time about a steady mean. Recently, [10] Dr. S. Anuradha, P. Priyadharshini (2014), studied and combined the effects of unsteady MHD free convective heat and mass transfer on the flow of viscous fluid past an impulsively started semi-infinite vertical plate with Soret effect. In the present analysis, it is proposed to study the effect of heat and mass transfer flow of viscous fluid through porous media and non-porous media. Hence our aim of this research is to compare the effect the speed of fluid in porous and non-porous medium for non- dimensional velocity U, concentration C, and Temperature profile T for different parameters Garsof Number, Modified Garshof Number, Prandtl Number and Schimidt Numbe. II. MATHEMATICAL FORMULATION We discussed an unsteady two dimensional natural convection flow of an incompressible viscous fluid past an impulsively started vertical plate through porous medium and non-porous medium. The positive x coordinate is measured along the plate in the direction of fluid motion and the positive y coordinate is measured normal to the plate. A uniform transverse magnetic field 0 B is imposed parallel to y-direction. The magnetic Reynolds number of the flow is taken to be small enough and the magnetic field is negligible in comparison with applied magnetic field and the magnetic lines are fixed relative to the fluid. The level of concentration of foreign mass is