Bifurcation to oscillatory flow of the natural convection around a vertical channel in rectangular enclosure

Numerical computations were performed for the heat transfer and fluid flow characteristics of natural convection with an internal vertical channel composed by a pair of parallel plates in a rectangular enclosure. The inner plates and the bounding wall of the enclosure were maintained at uniform but different temperatures. The plates were symmetrically arranged. Unsteady computation was performed to simulate the evolution process of the natural convection developing from the zero initial field. The cases of Ra = 2 × 10⁴, 2 × 10⁵ and 10⁶ were studied. A symmetrical steady solution was achieved for the case of Ra = 2 × 10⁴. For Ra = 2 × 10⁵ and 10⁶, time dependent asymmetrical processes were observed. The flow oscillating process seemed to be more complex at Ra = 2 × 10⁵ than that at Ra = 10⁶, which is quasi‐periodic with two frequencies.