Journal of Applied Sciences1812-56541812-5662Asian Network for Scientific Information10.3923/jas.2007.334.341AbdelkaderSlimaniMebroukRebhiAbdellahBelkacemKhadidjaBouhadef3200773A numerical analysis is performed to study the influence of the amplitude b of the sinusoidal undulation, of bottom wall, of an horizontal enclosure on the heat transfers by two-dimensional natural laminar convection. The hot wavy bottom wall and the cold straight top wall are kept isothermal at temperature equal, respectively to T_{h} and T_{c}. And the two vertical straight walls (right and left) are considered symmetrical. Results are presented in the form of local and global Nusselt numbers distribution for a selected range of Raleigh (10^{3}-10^{6}) and for four values (0.00, 0.15, 0.25, 0.35) of aspect ratios A = 2.b/a. Air of Pr = 0.71 in an enclosure of non dimensional length As = L/H equal to 4 is chosen as the flow model to examine the influences of the aspect ratios at various Raleigh Number. The natural convection equations are discretised, using an implicit finite difference method, based on the finite volume approach. The SIMPLE algorithm, assumes the linkage between velocities and pressure fields. The variation of the Raleigh Number has allows the obtaining of several types of flows and several forks between these flows. The flow in enclosure is characterized with recirculation zones over summits and in hollows, where the local Nusselt numbers is always minimal. The numerical results show that the flow and the heat transfer are strongly affected by the amplitude b. In a general the transfers developed within an enclosure by not flat topography are lower than those obtained in a horizontal and uniform enclosure of the same length.]]>Adjiout, L., O. Imine, A. Azzi and M. Beikadi,2002Asako, Y. and M. Faghri,1987Aydin, O., A. Unal and T. Ayhan,1999Chen, C.L. and C.H. Cheng,2002Dalal, A. and M.K. Das,2005Das, P.K. and S. Mahmud,2003Eisherbiny, S.M.,1996Gao, W., Lin and E. Lu,2000Hadjadj, A. and M.E. Kyal,1999Hamady, F.J., J.R. Lloyd H.Q. Yang and K.T. Yang,1989Kumar, B.V.R., P.V.S.N. Munhy and P. Singh,1998Kumar, B.V.R.,2000Kumar, B.V.R. and Shalini,2003Mahmud, S.,2002Mahmud, S., P.K. Das, N. Hyder and A.K.M.S. Islam,2002Mahmud, S. and A.K.M.S. Islam,2003Murthy, P.V.S.N., B.V.R. Kumar and P. Singh,1997Nishimura, T., Y. Ohori and Y. Kawamura,1984Oztop, H.F.,2005Ozoe, H., H. Sayma and S.W. Churchill,1975Patankar, S.V., 1980Peric, M.,1993Saidi, C., F. Legay and B. Pruent,1987Soong, C.Y., P.Y. Tzeng D.C. Chiang and T.S. Sheu,1996Varol, Y. and H.F. Oztop,2006Wang, G. and S.P. Vanka,1995