ABDELMADJID CHEHHAT2024-03-242024-03-242011http://dspace.univ-khenchela.dz:4000/handle/123456789/4517The subject of this paper is a direct numerical study of laminar and laminar-to-turbulent transient natural convection in a vertical duct, with a constant wall temperature, that exceeds the ambient fluid temperature. The governing equations are solved without modeling of the turbulence effect using a finite volume method. We presented the fields of velocity, temperature, and pressure as well as variation of the mean Nusselt number as a function of the Rayleigh number. The numerical simulation has been made for the Rayleigh number in the range from 1 to 105 for aspect ratios 3, 5, 8, and 12. The obtained results are compared with those given in the literature and a good agreement has been found.enArticle