mrep2017.pdf (3.22 MB)
Subcritical convection in rapidly rotating liquid metal spheres
presentation
posted on 2017-11-20, 21:42 authored by Nathanael SchaefferNathanael Schaeffer, Elliot Kaplan, Philippe Cardin, Céline Guervilly, Jérémie VidalPlanetary cores consist of liquid metals (low Prandtl number Pr) that convect as the core cools.
Here we study nonlinear convection in a rotating (low Ekman number Ek) planetary core using a fully 3D direct numerical simulation. At high rotation rate, the convection onsets in a turbulent state, and can be maintained well below the linear onset of convection (down to Ra=0.7 Racrit in this study).
We highlight the importance of the Reynolds stress, which is required for convection to subsist below the linear onset. In addition, the Péclet number is consistently above 10 in the strong branch.
We further note the presence of a strong zonal flow that is nonetheless unimportant to the convective state.
Our study suggests that, in the asymptotic regime of rapid rotation relevant for planetary interiors, thermal convection of liquid metals in a sphere onsets through a subcritical bifurcation.
Here we study nonlinear convection in a rotating (low Ekman number Ek) planetary core using a fully 3D direct numerical simulation. At high rotation rate, the convection onsets in a turbulent state, and can be maintained well below the linear onset of convection (down to Ra=0.7 Racrit in this study).
We highlight the importance of the Reynolds stress, which is required for convection to subsist below the linear onset. In addition, the Péclet number is consistently above 10 in the strong branch.
We further note the presence of a strong zonal flow that is nonetheless unimportant to the convective state.
Our study suggests that, in the asymptotic regime of rapid rotation relevant for planetary interiors, thermal convection of liquid metals in a sphere onsets through a subcritical bifurcation.
