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Journal Articles Journal of Fluid Mechanics Year : 2016

Reversal cycle in square Rayleigh-Bénard cells in turbulent regime

Abstract

We consider long-term data from direct numerical simulations of turbulent Rayleigh– Bénard convection inside two-dimensional (2-D) square cells. For the range of Rayleigh numbers Ra = 10 7 –10 8 and Prandtl numbers Pr = 3.0–4.3 considered, two types of flow regimes are observed: a regime consisting of consecutive reversals, when the global rotation switches sign; and a regime consisting of an extended cessation, when global rotation is absent. A filtering method discriminates these two regimes and allows us to identify two characteristic time scales for the former regime. A time rescaling is then used to tune our records to a common duration, thus putting into evidence a generic reversal cycle. This cycle is composed of three successive phases: acceleration, accumulation and release including a rebound event. We complement this view in terms of a global angular impulse, available mechanical energy, global kinetic energy and their corresponding transfer rates. For a particular realisation of a reversal, each phase is described in terms of the flow patterns (large diagonal roll, counter-rotating corner flows and thermal plumes) and tied to the corresponding energy processes. We conclude by performing linear as well as nonlinear stability studies to account for the triggering mechanism of the release.
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Dates and versions

hal-01429395 , version 1 (12-01-2017)

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Andrés Castillo-Castellanos, Anne Sergent, Maurice Rossi. Reversal cycle in square Rayleigh-Bénard cells in turbulent regime. Journal of Fluid Mechanics, 2016, 808, pp.614-640. ⟨10.1017/jfm.2016.647⟩. ⟨hal-01429395⟩
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