LARGE EDDY SIMULATION OF A SMALL POOL FIRE

Large eddy simulation has been applied to the prediction of a small pool fire experimentally tested by Venkatesh et al. The Smagorinsky's eddy viscosity model is used for subgrid-scale (SGS) turbulence closure and a modified laminar flamelet model (MLFM) based on the Cook and Riley approach is used for SGS combustion modeling. The predictions have captured the unique characteristics of small pool fires such as flame anchoring and double flame, as shown in previous theoretical analysis and experiments. The existence of the premixed zone of fuel and air, which is thought to be the reason for flame anchoring, is evidenced by the low gradient of temperature and mixture fraction near the burner rim. The experimentally observed double flame can be seen from both the predicted temperature contour and velocity vectors. For the mean temperature field where experimental data are available for quantitative comparison, the predictions with the MLFM are found to be in very good agreement with the data. In line with general expectations, the study also reveals that the predicted small pool fire is nearly axially symmetric. Comparison of the predictions with the two different SGS combustion models have highlighted the importance of SGS combustion modeling in capturing the fine details of such small pool fires. Considerable discrepancies have been found in the predictions of the velocity and temperature fields, and the predictions of the mixture fraction model indicate a slightly higher and more centered premixed flame near the burner rim.

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