ASSUMED JOINT PROBABILITY DENSITY-FUNCTION APPROACH FOR SUPERSONIC TURBULENT COMBUSTION

In a recent experiment, Cheng et al. used uv spontaneous vibrational R aman scattering and laser-induced predissociative fluorescence techniq ues for simultaneous measurements of temperature and concentrations of O2, H-2, H2O, OH, and N2 (and the rms of their fluctuations) in super sonic turbulate reacting shear layers. Because present computational t echniques are not suited for the prediction of all of the above measur ements, a new approach has been developed and is being used to predict all relevant flow properties and the rms of their fluctuations (where appropriate). The approach explores the use of a multivariate Beta PD F for concentrations. In particular, a version developed by Girimaji t o model scalar mixing in turbulent flows is employed. Predictions usin g this model were, in general, satisfactory in regions preceding ignit ion, but not in regions downstream of ignition. Part of the discrepanc y is a result of our current inability to relate Favre and time averag es.