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ICHMT DIGITAL LIBRARY ONLINE

ISSN 961-91393-0-5

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Year 2001

Volume 1 - CHT'01 - Advances in Computational Heat Transfer II
Proceedings of a Second Symposium - Palm Cove, Queensland, Australia, May 20 - 25, 2001

729 pages

CHALLENGES IN 'RANS' MODELLING OF TURBULENT THERMAL AND MAGNETIC CONVECTION

Kemo Hanjalic
Department of Multi Scale Physics, Faculty of Applied Sciences, Delft University of Technology, The Netherlands. Present affiliation: Marie Curie Chair, DMA, University of Rome "La Sapienza", Roma, Italy

ABSTRACT

Various levels of one-point turbulence closures for flows driven by thermal buoyancy are scrutinized with reference to recent direct numerical simulation (DNS) of some canonic buoyant flows. Major deficiencies, limitations and possible remedies for models improvement are discussed. Some recent developments in the differential second-moment closure and its algebraic variant, based on DNS term-by-term modelling, show significant improvements, as illustrated by several examples. However, when used in the conventional RANS (Reynolds-averaged Navier-Stokes) frame, none of the models is capable of reproducing effects of large-scale coherent eddy structures. It is demonstrated that the latter can be well predicted using a kind of very-large eddy simulation (VLES), which fully resolves large-scale structures and uses an algebraic RANS-type closure as the subscale model. The potential of this techniques, called T-RANS, is illustrated in examples of classic and magnetic Rayleigh-Benard convection over flat and wavy bottom walls at a range of Rayleigh numbers.