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Annual Review of Fluid Mechanics

Volume 50, 2018

Double-Diffusive Convection at Low Prandtl Number

Abstract

This work reviews present knowledge of double-diffusive convection at low Prandtl number obtained using direct numerical simulations, in both the fingering regime and the oscillatory regime. Particular emphasis is given to modeling the induced turbulent mixing and its impact in various astrophysical applications. The nonlinear saturation of fingering convection at low Prandtl number usually drives small-scale turbulent motions whose transport properties can be predicted reasonably accurately using a simple semi-analytical model. In some instances, large-scale internal gravity waves can be excited by a collective instability and eventually cause layering. The nonlinear saturation of oscillatory double-diffusive convection exhibits much more complex behavior. Weakly stratified systems always spontaneously transition into layered convection associated with very efficient mixing. More strongly stratified systems remain dominated by weak wave turbulence unless they are initialized into a layered state. The effects of rotation, shear, lateral gradients, and magnetic fields are briefly discussed.

Keyword(s): astrophysical fluid dynamics, convection, direct numerical simulations, double-diffusive convection, semiconvection, thermohaline convection

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2018-01-05
2024-04-26
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Double-Diffusive Convection at Low Prandtl Number
Annual Review of Fluid Mechanics 50, 275 (2018); https://doi.org/10.1146/annurev-fluid-122316-045234
/content/journals/10.1146/annurev-fluid-122316-045234
/content/journals/10.1146/annurev-fluid-122316-045234
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Supplemental Material

Supplementary Data

  • Supplemental Video 1: Temporal evolution of the compositional perturbations C in a simulation at Pr = τ = 0.33, R0-1 = 1.15, in a large domain of size 200d x 200d x 400d. After a brief phase of oscillatory double-diffusive convection (ODDC) (which can be difficult to see in this fixed-scale movie), eight layers spontaneously appear. The layers progressively merge until only two are left, at which point the movie ends. These layers ultimately merge much later (not shown). Simulation from Wood et al. (2013).

  • Article Type: Review Article

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