DOI: 10.1615/ICHMT.2009.TurbulHeatMassTransf
ISBN Print: 978-1-56700-262-1
ISSN: 2377-2816
The investigation of buoyant flows in differentially heated cavities
Краткое описание
This combined experimental and numerical investigation focusses on the effects of angle of inclination on buoyancy-driven flows inside tall, rectangular, differentially-heated cavities. It considers a rectangular cavity with an aspect ratio of 28.6, with its two long sides maintained at different temperatures and the two short, end-walls, thermally insulated. The Rayleigh number, based on the temperature difference and spacing on the long sides is 0.86 × 106 and the working fluid is air (Prandtl number 0.71). Experimental data, for the flow and thermal fields from a 2.18m × 0.52m × 0.0762m cavity, are presented for a cavity inclined at 60° to the horizontal, with the hot surface being the upper surface, and also for a 15° inclination angle, with the hot surface the lower one. Two-dimensional RANS computations are provided for a 60° and a 5° angle of inclination, with the hot surface being the upper one for both angles. A number of strategies are employed for the modelling of near-wall turbulence, including the analytical wall function (AWF) and also for the modelling of the turbulent stresses and heat fluxes. The experiments show that in the 60° stable case, the main differences from the vertical case are in the reduced levels of fluctuations of the velocity and temperature fields, while in the 15° unstable case, four longitudinal vortices are formed across the cavity which make the flow 3-dimensional and enhance mixing. Computations show that the AWF approach results in reliable flow and thermal predictions, while the prediction of temperature fluctuations improves with the introduction of 2nd-moment closures.