A computational study of turbulent natural convection in a side-heated near-cubic enclosure at a high Rayleigh number (Rn = 4.9 x 10(10)) is performed, aimed at gaining a better insight into the Bow pattern, particularly in the corner regions. Two types of thermal boundary conditions are applied at the horizontal walls: adiabatic and isothermal. Also, two kinds of lateral vertical walls are studied, corresponding to different experimental approximations of adiabatic conditions: the first by insulation and the second by imposing a stratified wall heating. The latter conditions ensure better flow two-dimensionality, with the temperature stratification on the vertical walls close to that expected in the parallel mid-plane. Computations are performed with both a two-dimensional (2D) and three-dimensional (3D) code using a low-Reynolds-number differential second-moment stress/flux closure and the related k-epsilon model (KEM) simplification. The numerical computations show that the second-moment closure (SMC) is better in capturing thermal three-dimensionality effects and strong streamline curvature in the corners. The KEM, however, still provides reasonable predictions of the first moments away from the corners.