Symmetry-breaking natural convection of water in an infinite vertical channel maintained at different temperatures

The transition to chaos in natural convection in a water layer between two differentially heated infinite vertical plates is investigated using direct numerical simulation under the Boussinesque approximation. After the primary instability of the base flow in the conduction regime at Rayleigh number Ra_c ∼ 58,000, a sequence of bifurcations leading to unsteady three-dimensional flow follow, and the flow eventually becomes chaotic at approximately 2Ra_c. In particular, at 6Ra_c, the symmetry between the upward flow near the hot wall and the downward flow near the cold wall breaks, and either the upward or downward flow appears with intermittent transition between them. As the Rayleigh number increases, the asymmetry increases and the transition between the upward and downward flows becomes less frequent, and only one of these two flows persists with net flow in one direction.