Experimental and numerical simulation of a buoyant fire

Abstract Measurements of velocity and temperature, using laser anemometry and fine wire thermocouples, respectively, are reported in a buoyant, turbulent natural gas flame burning on a porous refractory burner, 25 cm in diameter. Detailed comparisons are made between these measurements and numerical predictions using a parabolic formulation, k -ϵ turbulence modeling and a flamelet description for the combustion chemistry. The predictions are shown to be strongly dependent on initial conditions, particularly in relation to the scalar field which is crucial to the satisfactory reproduction of the effects of large scale flame motion so evident in fires driven wholly by buoyancy. Good agreement between prediction and experiment is observed for calculations initiated from measured values at a station immediately downstream from the first appearance of the buoyant instability, characteristic of such flames. The influence of the large scale, low frequency flowfield inhomogeneities on the measurement techniques for velocity and temperature is fully reviewed.

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