Investigation of the role of turbulent fluctuations on the time-averaged radiative emission in large-scale, turbulent pool fires

Abstract This paper presents an analysis of turbulence-radiation interaction (TRI) effects on the radiative emission. Correlations and auto-correlations that arise from the time-averaging of the emission term are investigated using global data numerically generated for large-scale ethanol and methanol pool fires. The data corresponds to points in the vicinity of the flame and within the hot gas plume. The numerical calculations consists of high-resolution, fully-coupled, large eddy simulation, with the participating medium is treated as non-gray using the weighted-sum-of-gray-gases model. The results show that TRI can increase the mean radiative emission by more than 100% and the magnitude of its effects is highly correlated to the intensity of temperature fluctuations. The blackbody radiation intensity auto-correlation I b ¯ has the dominant contribution to TRI, followed by the absorption coefficient-blackbody radiation intensity correlation, which is in general more important than the absorption coefficient auto-correlation κ P ¯ . Despite this, considering only fluctuations of temperature within the blackbody radiation intensity is not sufficient for an accurate prediction of the mean radiative emission. An approximation for I b ¯ and another for κ P ¯ are also tested; while the former performs reasonably well, yielding average errors of around 17%, the latter performs quite poorly, with its associated errors surpassing 100%.