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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-421-2

International Heat Transfer Conference 15
August, 10-15, 2014, Kyoto, Japan

Turbulent Thermal Convection in an Enclosure with Differently Inclined Horizontal Wall: a LES Study

Get access (open in a dialog) DOI: 10.1615/IHTC15.cnv.009209
pages 1653-1664

Abstract

We performed a well-resolved Large-Eddy Simulations (LES) of turbulent thermal convection of air, confined within an enclosure with differently inclined lower wall. The lower wall is heated, the top wall is cooled (both walls kept at constant temperature), and all side walls are adiabatic. We considered two basic configurations of the lower wall, so called the "V" and "Λ" shapes under different inclination angles. We covered an intermediate range of Rayleigh numbers, i.e. 107Ra≤109. Two types of the subgrid turbulence closures (SGS) are used. The first is the Smagorinsky-Lilly [1] model with additional wall-damping of the turbulent viscosity in the proximity of walls, [2]. To eliminate need for the near-wall turbulent viscosity damping, a recently proposed SGS model of Vreman [3] is introduced, which is suitable for the transport phenomena where different flow regimes can coexist. A simple gradient diffusion hypothesis (SGDH) model for the unresolved turbulent heat flux is employed. The SGS model of Vreman [3] proved to produce integral heat transfer in very close agreement with the available DNS results for the flat lower wall configuration, and, as such, is recommended for future use in simulating thermal buoyancy driven flows. Numerical simulation provided detailed insights into the dynamics of the flow structure and heat transfer reorganization caused by changing lower wall inclination angles. We found that the wall heat transfer can be significantly affected by changes of the lower wall inclination. The integral wall-heat transfer was enhanced up to 25% for Ra=109 and up to 14% for Ra=107. It is shown that the heat transfer enhancement is caused by the large coherent structure reorganization.