A priori validation of subgrid-scale models for astrophysical turbulence

摘要: We perform a-priori validation tests of subgrid-scale (SGS) models for the turbulent transport momentum, energy and passive scalars. To this end, we conduct two sets high-resolution hydrodynamical simulations with a Lagrangian code: an isothermal box rms Mach number 0.3, 2 8, classical wind tunnel where cold cloud traveling through hot medium gradually dissolves due to fluid instabilities. Two SGS are examined: eddy diffusivity (ED) model wildly adopted in astrophysical "gradient model" Clark et al. (1979). find that both predict magnitude terms equally well (correlation coefficient > 0.8). However, gradient provides excellent predictions on orientation shape while ED predicts poorly both, indicating isotropic diffusion is poor approximation instantaneous transport. The best-fit range [0.16, 0.21] momentum transport, Schmidt Prandtl close unity, [0.92, 1.15].