Comparison of the ASOM model and the PDF transport equation model in simulating turbulent jet combustion

A composition probability density function transport equation (PDF) model and an algebraic second-order moment (ASOM) model of turbulent combustion are used to simulate a methane-air turbulent jet flame, measured by Sandia National Laboratory. The prediction results are then compared with the experimental data, which shows that the predicted time-averaged temperature and species concentration using both of the models are, in most region, in good agreement with the experimental data. Considering that the computation time of the PDF model is approximately 100 times that of the ASOM model, the ASOM model is considered to be more suitable for engineering application, The statistical results of the PDF model predictions show that the correlations of the methane concentration fluctuation with the oxygen concentration fluctuation, of the temperature fluctuation with the methane/oxygen concentration fluctuation, and of the reaction-rate coefficient fluctuation with the methane/oxygen concentration fluctuation, show the similar trends with the products of the gradients of corresponding time-averaged variables, hence validating the closure assumptions made in the ASOM model.