[GTP] Seminar tomorrow: Zbigniew Piotrowski

[Silvia Gentile]

HAO Colloquium Series
(Refreshments served)
Speaker: Zbigniew Piotrowski—NCAR/GTP
Time: 1:30 pm
Date: Wednesday, January 19, 2011
Location: CG-1, South Auditorium

Title: Under-resolved simulations of Rayleigh-Benard convection; effects 
of anisotropic viscosity and Prandtl number Problems


Abstract:
The main stream of interest in studies of geophysical and astrophysical 
convection falls in the regime of large Rayleigh numbers. Rapid progress 
in computational technology already enables global-scale simulations of 
convective fields at unprecedented mesoscale resolutions. This in turn 
enables calculations free of convection parameterizations, in the spirit 
of large-eddysimulation (LES). Ironically, the simulated (as opposed to 
parameterized) convection can be largely under-resolved at the mesoscale 
resolutions, making numerical solutions sensitive to ad hoc filtering 
present in some form in all computational models. The latter shifts the 
virtual reality of convection toward moderate and low Rayleigh number 
regimes, rich in intriguing and attractive forms of the structural 
organization, yet unrealistic for the specified external parameter 
range. In the recent paper [Piotrowski et al., On numerical 
realizability of thermal convection, J. Comput. Phys. 228 (2009) 
6268-6290], the authors have documented the sensitivity of convection 
organization to the anisotropic viscosity at a fixed finite Prandtl 
number. The current work, in progress, extends the linear stability 
theory of Piotrowski et al. on the Rayleigh-Benard convection at low-to 
moderate Rayleigh numbers and anisotropic Prandtl numbers, with an aim to
mimic disparate approximations to the governing equations, not uncommon 
in geophysical fluid solvers.
Asymptotic predictions of the linear theory are discussed and 
illustrated with numerical examples.

-- 
Silvia Gentile
NCAR IMAGe
1850 Table Mesa Drive
Boulder, CO 803035
www.image.ucar.edu