期刊
ASTROPHYSICAL JOURNAL
卷 731, 期 1, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/731/1/66
关键词
convection; hydrodynamics; planets and satellites: general; stars: interiors
资金
- NSF [NSF-0807672]
- NASA [NNG05GG69G, NNG06GD44G, NNX07A2749]
- NSF-MRI
- Direct For Mathematical & Physical Scien [0807672] Funding Source: National Science Foundation
- Division Of Astronomical Sciences [0807672] Funding Source: National Science Foundation
Double-diffusive convection, often referred to as semi-convection in astrophysics, occurs in thermally and compositionally stratified systems which are stable according to the Ledoux criterion but unstable according to the Schwarzschild criterion. This process has been given relatively little attention so far, and its properties remain poorly constrained. In this paper, we present and analyze a set of three-dimensional simulations of this phenomenon in a Cartesian domain under the Boussinesq approximation. We find that in some cases the double-diffusive convection saturates into a state of homogeneous turbulence, but with turbulent fluxes several orders of magnitude smaller than those expected from direct overturning convection. In other cases, the system rapidly and spontaneously develops closely packed thermo-compositional layers, which later successively merge until a single layer is left. We compare the output of our simulations with an existing theory of layer formation in the oceanographic context and find very good agreement between the model and our results. The thermal and compositional mixing rates increase significantly during layer formation and increase even further with each merger. We find that the heat flux through the staircase is a simple function of the layer height. We conclude by proposing a new approach to studying transport by double-diffusive convection in astrophysics.
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