Aspects of turbulent combustion

A complete second-order closure program for the investigation of chemically reacting turbulent flowfields is being developed. Many of the turbulence models being used have been developed and tested during previous studies of a variety of incompressible and compressible shear flows. A number of additional scalar correlations have to be modeled for chemically reacting flows, and a "typical eddy" model has been developed for the joint probability density function for all of the scalars. A simpler model in which higher-order scalar correlations are set zero also is being used. The program has been extended recently to multispecies, multistep chemical reactions. Computations have been performed using the secondorder closure program to study the turbulence-chemistry interaction in deuterium fluoride chemical laser flows and in a hydrogen-air diffusion flame. The results demonstrate the importance of the inclusion of the concentration and temperature fluctuation correlations in turbulent reacting flows. Nomenclature