The Influence of Turbulent Fluctuations on the Radiation Intensity Emitted from the Core Region of Exhaust Plumes

Turbulent radiation statistics are reported for the core region of three subsonic exhaust plumes. Spectrally integrated radiation inte nsity measurements were acquired using an infrared camera fitted with a narrowband filter (4.34+/-0.1 µm). Unsteady two-dimensional simulations were used to predict time-resolved and average temperature and partial pressure values of the exhaust species in the flow. The radiation intensity along diametric paths was calculated using the scalar values and a narrowband radiation intensity solver. Mean intensity values typically within agreed within 25% or better when using average and time-resolved scalar values. This indicates that tu rbulent fluctuations have little effect on the radiation intensity emitted from the cores of jets. Fluctuations in the measured radiation intensity increased markedly beyond the plume core. This corresponded with an increase in the skewness and kurtosis of the radiation intensit y. These findings indicate that the size of the core of a heated jet might be estimated using turbulent radiation statistics.