Evaluation of a subgrid-scale model for the temperature fluctuations in reacting turbulence

Abstract

A direct numerical simulation database is used to develop a new model for the subgrid-scale temperature fluctuations for use in the large-eddy simulations of turbulent hypersonic flows. The model uses a probability density representation of the temperature fluctuations where the parameters that describe the probability density function (PDF) are based on local resolved-scale flow conditions. The model is calibrated and tested by comparison to direct numerical simulation results. The simple single-variable PDF captures the temperature fluctuations reasonably, but it over-predicts the magnitude of the density fluctuations and the rate of reaction. This is caused by the coupling between the temperature and density (or pressure) fluctuations in the compressible flow. Therefore, a more complicated multiple-variable or conditional PDF model is required.