Evaluation and optimization-based modification of a model for the mean radiative emission in a turbulent non-reactive flow

Abstract

An analysis on turbulence-radiation interaction (TRI) effects and an evaluation and modification of a model for the mean radiative emission are presented, in the context of a non-reactive channel flow of a high temperature homogeneous participating gas. Large-eddy simulation is adopted to generate transient data that can be compared to independent calculations initialized with mean temperature and flow fields. Both the gray gas and the weighted-sum-of-gray-gases models are used to solve the radiative heat transfer, as a means of investigating how the consideration or not of the spectral variation of radiative properties influences TRI effects. Results show an overall small impact of TRI on both the mean radiative heat flux and the mean radiative heat source, but relatively greater effects are observed when the spectral dependence of the problem is not neglected. The model for the radiative emission does not have a good accuracy for the cases studied in this paper, probably because it was developed for higher temperature fluctuation intensities than the range predominant in the simulations. A modification on the values of two coefficients associated with the model, performed based on an optimization methodology, leads to a considerable reduction in the error in the predicted mean radiative heat flux compared to solutions fully neglecting turbulent fluctuations. Although the improvement in the estimation of the mean radiative heat source is not so substantial, in most of the domain this quantity is better predicted with the modified model than without it.