Rayleigh--Taylor turbulence in two dimensions

Description

The first consistent phenomenological theory for two and three dimensional Rayleigh--Taylor (RT) turbulence has recently been presented by Chertkov [Phys. Rev. Lett. 91 115001 (2003)]. By means of direct numerical simulations we confirm the spatio/temporal prediction of the theory in two dimensions and explore the breakdown of the phenomenological description due to intermittency effects. We show that small-scale statistics of velocity and temperature follow Bolgiano-Obukhov scaling. At the level of global observables we show that the time-dependent Nusselt and Reynolds numbers scale as the square root of the Rayleigh number. These results point to the conclusion that Rayleigh-Taylor turbulence in two and three dimensions provides a natural physical realization of the long sought ``ultimate state of thermal convection'' [Lohse and Toschi, Phys. Rev. Lett. 90 034502 (2003)].

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