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Fourth International Symposium on Turbulence and Shear Flow Phenomena
June, 27-29, 2005, Marriot Hotel, Williamsburg, Virginia, USA

DOI: 10.1615/TSFP4

NUMERICAL ANALYSIS OF RAYLEIGH-BERNARD CONVECTION USING LARGE EDDY SIMULATION AT HIGH RAYLEIGH NUMBERS

pages 983-988
DOI: 10.1615/TSFP4.1630
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RESUMO

Turbulent Rayleigh-Bernard convection in a 6 : 1 domain has been numerically studied using LES for Rayleigh numbers ranging from 6.3 × 105 to 109. The results show reasonable agreement with previous experimental and DNS analysis. The scaling analysis with the present LES data shows that Nu may be scaled by a single relation of Nu = 0.24Ra0.26, which lies approximately in line with the theoretical scaling for hard turbulence regime. In general, it was found that each characteristic scale considered can be fitted reasonably well with a single scaling relation. Nonetheless, for scales defined from thermal fluctuations and from properties in the off-wall mixed layer, to some extent, the transition from soft to hard turbulence has been reflected in the Ra-scaling between Ra = 107 and 4 × 107. The transition is characterized by the thermal dynamics and, as Ra number increases, its occurrence seems to be more detectable in the mixed layer than near the wall.

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