# I. Introduction ecent development in the field of heat and mass transfer through porous medium has led to the intensive research, as a result of that, many researchers have shown significant interest to explore the various aspects during the last few decades. The fundamental concept about the flow through porous medium and various applications encompassing it has been well documented by the recently published books by Nield and Bejan [1], Ingham and Pop [2], Vafai [3], Pop and Ingham [4] and, Bejan and Kraus [5]. The various aspects of the convective heat transfer pertaining to the various physical and geometrical parameters, is thoroughly discussed in the available literature . Especially the double diffusion phenomenon, which finds various industrial and technological applications such as; drying of vegetables, drying of seeds, migration of pollutants through soil, cooling of nuclear reactor and many more, has made eminent researchers to delved in to this particular area, to understand the micro details of the subject. It is evident from the literature that the specific geometries such as cavities find special applications in industries, therefore the research pertaining to the flow through porous cavities is of significant importance which is reflected in the literature [31][32][33][34][35]. The present work is an extension of [24] where only assisting flow was analyzed. The current work tries to understand the double diffusion due to opposing flow. The mathematical model of square porous cavity and its relevant equations are given in [24]. It should be noted that the current work focusses only on opposing flow caused by negative value of buoyancy ratio where thermal and concentration buoyancy opposes each other. # II. # Results and Discussion The results are discussed with respect to isotherms and iso-concentration lines in the porous medium. Figure 1 shows the heat and mass transfer behavior in terms of temperature, concentration and streamlines. The left column of figure corresponds to N=-0.2 where as right column belongs to N=-0.5. The whole figure is obtained by maintaining Ra=100, Rd=0.5 and Le=5. It is found that the isotherms move towards the hot surface due to change in N from -0.2 to -0.5. This indicates that as the magnitude of two buoyancy forces increases the heat transfer rate increases. Similar effect is seen with respect to mass transfer also. The concentration lines moves towards the hot surface when magnitude of opposing buoyancy increases. The penetration of higher concentration deep into porous region increased due to change in N from -0.2 to -0.5. # III. Conclusion Heat and mass transfer in a square porous cavity due to opposing buoyancy is studied. It is found that the heat transfer increases with increase in magnitude of opposing buoyancy forces. radiation on double conjugate diffusion in a porouscavity, AIP Conference Proceedings 1728, 020283(2016); doi: 10.1063/1.4946334.28. Irfan Anjum Badruddin, N. J. Salman Ahmed,Abdullah A. A. A. Al-Rashed, Jeevan Kanesan,Sarfaraz Kamangar, H. M. T. Khaleed, Analysis ofHeat and Mass Transfer in a Vertical Annular PorousCylinder Using FEM, Transp. Porous Media, 91(2),697-715(2012).29. Trevisan, Osvair and Adrian Bejan, Combined heatand mass transfer by natural convection in a porousmedium, Advances in Heat Transfer 20315-352 (1990). 30. G.H.R. Kefayati, Simulation of double diffusive natural convection and entropy generation of power-law fluids in an inclined porous cavity with Soret andYear 2017Dufour effects (Part I: Study of fluid flow, heat andmass transfer). Int. J. Heat Mass Transfer, Volume94, March, Pages 539-581 (2016). 31. Soto-Meca, J. Serna, F.J.Velasco. Heat and mass transfer enhancement in a double diffusive mixed convection lid cavity under pulsating flow. Comp. & Chem. Engg. Jul 30 (2016). 32. R. Rebhi, M. Mamou, P. Vasseur, M.Alliche, Form drag effect on the onset of non-linear convection and Hopf bifurcation in binary fluid saturating a tall porous cavity. Int. J. Heat Mass Transfer. Sep 30; 100: 178-90 (2016). 33. C.S. Balla, K. Naikoti, Soret and Dufour effects on free convective heat and solute transfer in fluid saturated inclined porous cavity. Engg. Sci. Tech., Int. J. Dec 31; 18(4): 543-54 (2015). 34. K. Al-Farhany, A. Turan, Numerical study of double diffusive natural convective heat and mass transfer in an inclined rectangular cavity filled with porous medium. Int. commun. Heat Mass Transfer, Feb 29; 39(2): 174-81 (2012). 35. Serrano-Arellano J, Gijon-Rivera M. Conjugate heat and mass transfer by natural convection in a square cavity filled with a mixture of Air-CO 2. Int. J. Heat Mass Transfer, Mar 31; 70: 103-13 (2014).Global Journal of Researches in Engineering ( ) Volume XVII Issue IV Version I A Global Journal of Researches in Engineering R© 2017 Global Journals Inc. (US) © 2017 Global Journals Inc. (US) * DNield ABejan Convection in Porous Media New York Springer Verlag 2006 3rd * Transport phenomena in porous media DBIngham IPop Pergamon, Oxford 1998 * Hand book of porous media KVafai 2000 Marcel Dekker New York * Convective heat transfer: Mathematical and computational modeling of viscous fluids and porous media DBPop Ingham 2001 Pergamon, Oxford * Heat transfer handbook A.D. 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