Abstract
Reversal motions are often observed in the system with a parity symmetry. Reversals of large-scale circulation also exist in the case of thermally driven turbulence in a container. We investigate the onset of chaotic reversals of thermal convection cell in a two-dimensional square cavity using direct numerical simulation. In this system, the first observable reversal is related to the one-vortex state. The symmetric pair of the stable one-vortex periodic orbits approach each other as Rayleigh number increases. These orbits touch the steady saddle, which exists on the basin boundary between them, and become the homoclinic orbits to the saddle. This event is the homoclinic explosion which leads to the onset of chaotic reversals.
