Abstract
Recent advances in modeling Rayleigh-Benard convection have demonstrated
the existence of turbulent superstructures, whose life and morphology
largely varies with Rayleigh (Ra) and Prandtl (Pr) numbers. These
structures appear as a two scale phenomena, where small scale rolls
organize in larger convection cells, and can be modelled only in 3D on a
simulation box characterized by a very large (>10)
width/height (W/L) ratio, and sufficiently refined to resolve the
boundary layer up to Ra = 108 (>100
divisions in height) and to Ra = 1010
(>200 divisions). To achieve this goal, we use our own 3D
Parallel Python implementation of the Lattice Boltzmann Method, tested
to run with linear efficiency on thousands of cores. We show the
dependency of horizontal fluctuations of RMS of temperature and vertical
velocity in the middle of the box and illustrate how the superstructures
emerge for W/L ratios of Terrestrial Planets and Super Earths, and
quantify the duration of these superstructures and the likely
implications for the evolution of their surface features. The effect of
the P/T dependent viscosity and thermal conductivity is finally
discussed.