This effort entails the validation of a RANS turbulent scalar transport model (SFM) for high speed propulsive flows, using new experimental data sets and accompanying large-eddy simulation (LES) solutions. The SFM has been used to predict local values of the turbulent Prandtl and Schmidt numbers and also provides the rms scalar fluctuation values that are used with assumed PDF models for turbulent combustion. Performing the experimental work in unison with LES studies ensures that the two sets of data will be fully compatible, and may be used to support SFM model validation. Work to date indicates some deficiencies in the present SFM model for high speed mixing problems where the two streams have very different densities, which we will attempt to resolve in this program. PIV data for the transverse injection of hot air and helium/nitrogen mixtures into a Mach 3.5 stream will be obtained in unison with LES studies to yield scalar fluctuation data not readily obtained in experiments. SFM upgrades will be performed using this unified data. Experiments will be performed by Dr. Seiner and coworkers at U. Miss using a new 12"x12" trisonic tunnel and existing slot/round jet injector models.