Efficient Turbulent Compressible Convection in the Deep Stellar Atmosphere

This paper reports an application of gas-kinetic BGK scheme to the computation of turbulent compressible convection in the stellar interior. After incorporating the Sub-grid Scale (SGS) turbulence model into the BGK scheme, we tested the effects of numerical parameters on the quantitative relationships among the thermodynamic variables, their fluctuations and correlations in a very deep, initially gravity-stratified stellar atmosphere. Comparison indicates that the thermal properties and dynamic properties are dominated by different aspects of numerical models separately. An adjustable Deardorff constant in the SGS model $c_\mu=0.25$ and an amplitude of artificial viscosity in the gas-kinetic BGK scheme $C_2=0$ are appropriate for current study. We also calculated the density-weighted auto- and cross-correlation functions in Xiong's (\cite{xiong77}) turbulent stellar convection theories based on which the gradient type of models of the non-local transport and the anisotropy of the turbulence are preliminarily studied. No universal relations or constant parameters were found for these models.