On numerical realizability of thermal convection

  • Authors:

  • Zbigniew P. Piotrowski;Piotr K. Smolarkiewicz;Szymon P. Malinowski;Andrzej A. Wyszogrodzki

  • Affiliations:

  • Institute of Geophysics, University of Warsaw, Warsaw, Poland and Institute of Meteorology and Water Management, Warsaw, Poland;National Center for Atmospheric Research, Boulder, CO 80307, USA;Institute of Geophysics, University of Warsaw, Warsaw, Poland;National Center for Atmospheric Research, Boulder, CO 80307, USA

  • Venue:
  • Journal of Computational Physics
  • Year:
  • 2009

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Abstract

Astounded at the regularity of convective structures observed in simulations of mesoscale flow past realistic topography, we investigate the computational aspects of a classical problem of flow over a heated plane. We find that the numerical solutions are sensitive to viscosity, either incorporated a priori or effectively realized in computational models. In particular, anisotropic viscosity can lead to regular convective structures that mimic naturally realizable Rayleigh-Benard cells, which are unphysical for the specified external parameter range. Details of the viscosity appear to play a secondary role; that is, similar structures can occur for prescribed constant viscosities, explicit subgrid-scale turbulence models, ad-hoc numerical filters, or implicit dissipation of numerical schemes. This implies the need for a careful selection of numerical tools suitable for convection-resolving simulations of atmospheric circulations. The implicit large-eddy-simulation (ILES) approach using non-oscillatory schemes is especially attractive, as for under-resolved calculations it reproduces well the coarsened results of finely-resolved boundary layer convection.