Progress in Practical Scalar Fluctuation Modeling for High-Speed Aeropropulsive Flows

Abstract

A model for predicting scalar fluctuations in aeropropulsive flows is evaluated for various applications ranging from simple low-speed jets to more complex supersonic fuel/air injection flows. The model is formulated within a compressibility-corrected RANS k-e turbulence framework utilizing additional equations to calculate scalar variances along with their dissipation rates. Local values of turbulent Prandlt and Schmidt numbers are evaluated from these scalar variances along with the turbulent kinetic energy and its dissipation rate using time-scale relations. Applications involving both temperature and species transport yield non-unity turbulent Lewis numbers, which the current model predicts in a qualitatively reasonable manner. Good agreement with available data for mean and fluctuating scalar quantities is obtained for flat plates, round jets and mixing layers. Preliminary calculations for fuel injection in a hypersonic scramjet combustion environment show marked variations of turbulent Prandtl and Schmidt numbers, and turbulent Lewis numbers well above unity.