Mie scattering measurements of probability density functions in compressible mixing layers

Planar Mie scattering visualizations in compressible mixing layers are used to compute the probability density function (PDF) of a passive scalar. Mixing layer flows with relative Mach numbers of 0.63 and 1.49 are studied. Ethanol condensation is used to generate both scalar transport seeding and product formation seeding. All PDFs exhibit a marching behavior. The condensation process in the product formation seeding is modeled to provide an estimate of the error embedded in the scalar transport PDFs. The mixing efficiency is found to be 0.56 in the product formation experiments, and the overprediction of mixing efficiency by the scalar PDFs is estimated to be 11 percent, based on results from the ethanol condensation model. (Author)