Three-dimensional large eddy simulations (LES) of two buoyant flows were performed in conjunction with a Smagorisky turbulence model. The flows included a non-reacting helium plume previously simulated with two-dimensional simulations and a methane/air turbulent diffusion flame. In comparison with the previous two-dimensional simulation results, the three-dimensional LES results for the helium plume show much better agreement with the available experimental data. A relatively simple combustion model involving Lagrangian thermal elements with a single empirical constant involving the time to burn out of notional fuel parcels was adequate for obtaining reasonable predictions of the mean velocity and vorticity fields. The model also captured the temperature distribution patterns in the methane/air diffusion flames reasonably well. The agreement between the measurements and predictions for these two flows establishes the basic capabilities of LES for buoyant fire applications.
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