Unsteady coupled thermal boundary layers induced by a fin on the partition of a differentially heated cavity

The transition from steady to unsteady coupled thermal boundary layers induced by a fin on the partition of a differentially heated cavity was numerically investigated. Numerical simulations were performed over the range of Rayleigh numbers from Ra = 107 to 2 × 1010 (Pr = 6.63). The temporal development and spatial structure of natural convection flows in the partitioned cavity with a fin are described. It has been demonstrated that the fin may induce a transition to unsteady coupled thermal boundary layers and the critical Rayleigh number for the occurrence of the transition is between 3.5 and 3.6 × 108. Furthermore, the peak frequency of the oscillations induced by the fin has been obtained through spectral analysis. It has been found that the flow rate through the cavity with a fin is larger than that without a fin under unsteady flow, indicating that the fin may improve unsteady flow in the partition cavity.