From cat's eyes to disjoint multicellular natural convection flow in tall tilted cavities

Numerical results of two-dimensional natural convection problems, in air-filled tall cavities, are reported to study the change of the cat's eyes flow as some parameters vary, the aspect ratio A and the angle of inclination ϕ of the cavity, with the Rayleigh number Ra mostly fixed; explicitly, the range of the variation is given by 12⩽A⩽20 and 0°⩽ϕ⩽270°; about Ra=1.1×10. A novelty contribution of this work is the transition from the cat's eyes changes, as A varies, to a disjoint multicellular flow, as ϕ varies. These flows may be modeled by the unsteady Boussinesq approximation in stream function and vorticity variables which is solved with a fixed point iterative process applied to the nonlinear elliptic system that results after time discretization. The validation of the results relies on mesh size and time-step independence studies.