Title: Large Eddy Simulation of turbulent thermal convection using a Mixed Scale Diffusivity Model

Authors: A. Sergent, P. Joubert, P. Le Quere

Addresses: LIMSI, CNRS, BP 133, 91403 Orsay, France. ' LEPTAB, Universite de La Rochelle, Avenue M. Crepeau, 17042 La Rochelle cedex 1, France. ' LIMSI, CNRS, BP 133, 91403 Orsay, France

Abstract: The Mixed Scale Diffusivity Model, originally developed in the case of the differentially heated cavity, is applied to compute turbulent Rayleigh-Benard flow in an infinite fluid layer at Pr = 0.71 for a large range of Rayleigh numbers (6.3 × 10⁵ – 2 × 10¹¹). The effect of this SGS modelling, which adjusts locally the SGS diffusivity to the thermal scales of the flow and results in variable Pr_SGS like the dynamic approach, is emphasised by comparison with LES and TRANS literature data. A single scaling regime is found in a range of Rayleigh numbers 6.3 × 10⁵ – 2 × 10¹⁰, whose properties include the Ra^0.302 scaling law for the Nusselt number and for the thermal boundary layer thickness, in agreement with the experimental correlation of Niemela et al. (2000). The first indication of a transition towards a new regime appears above Ra = 10¹¹.

Keywords: thermal convection; Rayleigh-Benard; turbulence modelling; large eddy simulation; CFD; computational fluid dynamics; turbulent flows.

DOI: 10.1504/PCFD.2006.009481

Progress in Computational Fluid Dynamics, An International Journal, 2006 Vol.6 No.1/2/3, pp.40 - 49

Published online: 05 Apr 2006 *

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