Natural-convection flows are investigated using regularized Oberbeck–Boussinesq equations which are solved by the finite element method with the same order of approximating functions. Coherent structures are revealed in a square channel with heat-insulated side walls and ends of different temperature under conditions of certain orientation to the direction of the effect of gravity on the dividing line between the counter flows of hot and cold air. Jet flows are calculated which develop from the heated internal walls of a “submerged” channel. It is demonstrated that a maximum of the intensity of flows exists under conditions of variation of the channel orientation with respect to the direction of the force of gravity. For a square channel, the maximum of intensity is observed for nonzero angle between the longitudinal axis and the direction of the effect of gravity; in the case of a “submerged” channel, this maximum is observed for zero angle.