8 April 2013 to 3 May 2013
Nordita
Europe/Stockholm timezone

Implicit large-eddy simulation of rotating turbulent convection with the EULAG code

Not scheduled
132:028 (Nordita)

132:028

Nordita

Talk

Speaker

Gustavo Guerrero (Solar Physics, HEPL, Stanford University)

Description

Solar and stellar activity is thought to be the result of the collective effects of turbulent-rotating convection. It develops large-scale flow patterns like differential rotation and meridional flows, induces the generation of magnetic fields as well as enhances their diffusion. In this work we explore the first part of the process, namely, the physic governing the development of the large-scale flows. We performed anelastic global simulations of rotating convection in a model whose stratification resembles that of the solar interior. The numerical models correspond to the so called implicit large-eddy simulations since they capture the contribution of the small, non-resolved, scales through the non-linear computation of the numerical viscosity. The amount of viscosity is the minimal necessary to keep the system stable, so that the Reynolds number is maximized for any resolution. We obtained two different regimes of rotation, with zonal flows accelerated either in the direction of rotation (solar-like) or in the opposite direction. Simulations with different rotation rates and different convection strength indicate that the resulting pattern depends on the ratio between buoyancy and Coriolis forces (i.e., the Rossby number). Thanks to the presence of a strongly subadiabatic layer at the bottom of the domain, we have been able to reproduce regions of strong radial shear similar to the solar tachocline. Similarly, enhanced superadiabaticity at the top of the domain results in the formation of a near-surface shear layer located mainly at lower latitudes. The models develop a gradient of potential temperature at the base of the convection zone and the stable region, however, it does not propagates across the entire domain. Thus, the baroclinicity remains small and so the rotation iso-contours align in cylinders in agreement to the Taylor-Proudman balance. Simulations with different resolution are also presented and the convergence of the sub-grid scale method is discussed.

Primary author

Gustavo Guerrero (Solar Physics, HEPL, Stanford University)

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