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Convection in a rapidly rotating spherical shell at infinite Prandtl number: transition to vacillating flows

1992; Elsevier BV; Volume: 72; Issue: 3-4 Linguagem: Inglês

10.1016/0031-9201(92)90204-9

1872-7395

K. Zhang,

Geology and Paleoclimatology Research

Stability of steadily drifting three-dimensional finite-amplitude columnar rolls at infinite Prandtl number, in a rapidly rotating spherical fluid shell of radius ratio η = rir0 = 0.4, is examined. Two types of instability, modulational and amplitude-vacillating, are found. Both instabilities result in the simultaneous breaking of temporal and spatial symmetry of the drifting columnar rolls. Amplitude-vacillating instability leads to a periodic change in amplitude without substantially changing the pattern or scale of convection. Modulational instability gives rise to the transition from the regularly placed columnar rolls to ones which are strongly spatially modulated on a large scale. A dramatic enhancement in heat transfer is produced in both cases through the combined effects of time-dependence and spatial modulations.