2017/01/31 by Jan Verhoeven, Gary A. Glatzmaier
Engineering · Physics and Astronomy · #Compressibility #Compressible flow #Computational Fluid Dynamics and Aerodynamics #Convection #Fluid Dynamics and Turbulent Flows #Mach number #Marginal stability #Nonlinear system #Prandtl number #Solar and Space Plasma Dynamics #Turbulence #Turbulent Prandtl number #astro-ph.EP #physics.flu-dyn
paper · pdf · doi:10.1080/03091929.2017.1380800
23 pages, 8 figures
openalex created_date 2017/01/26 · arxiv created 2017/09/21 · arxiv updated 2017/09/22 · openalex publication_date 2017/10/06 · openalex updated_date 2026/08/05
The validity of the anelastic approximation has recently been questioned in the regime of rapidly-rotating compressible convection in low Prandtl number fluids (Calkins, Julien and Marti, Proc. R. Soc. A, 2015, vol. 471, 20140689). Given the broad usage and the high computational efficiency of sound-proof approaches in this astrophysically relevant regime, this paper clarifies the conditions for a safe application. The potential of the alternative pseudo-incompressible approximation is investigated, which in contrast to the anelastic approximation is shown to never break down for predicting the point of marginal stability. Its accuracy, however, decreases close to the parameters corresponding to the failure of the anelastic approach, which is shown to occur when the sound-crossing time of the domain exceeds a rotation time scale, i.e. for rotational Mach numbers greater than one. Concerning the supercritical case, which is naturally characterised by smaller rotational Mach numbers, we find that the anelastic approximation does not show unphysical behaviour. Growth rates computed with the linearised anelastic equations converge toward the corresponding fully compressible values as the Rayleigh number increases. Likewise, our fully nonlinear turbulent simulations, produced with our fully compressible and anelastic models and carried out in a highly supercritical, rotating, compressible, low Prandtl number regime show good agreement. However, this nonlinear test example is for only a moderately low convective Rossby number of 0.14.