Advances in Scalar Fluctuation Modeling and Automated Validation Tools for High-Speed Propulsion Applications

Abstract

A scalar fluctuation model (SFM) that solves partial differential equations for energy/species variance and corresponding dissipation rates is presented, along with several applications to high-speed fuel/air mixing problems. The model is implemented in a kepsilon turbulence model framework with unified compressibility and low Re extensions, specialized for high speed aero-propulsive flow applications. It is used to predict the spatial variation of turbulent Prandtl and Schmidt numbers using time-scale relations, providing more accurate and reliable solutions than those based on user-specified average-values. Over the past several years, the authors and coworkers have systematically upgraded the SFM to treat flows of increasing complexity, using a “building-block” approach to ensure that modifications made to improve the analysis of more complex cases will not degrade the model performance in analyzing fundamental cases. A GUI-driven building-block data base (BBDB) tool has been developed to facilitate the validation/calibration process, which contains the various data sets we are working with (experimental and LES) along with grids and solution files, and scripts to take CFD output and put it into the format required to compare with the data. This paper will describe the latest version of the SFM, its application to select fundamental cases in the validation data base, and a detailed description of its analysis of the SCHOLAR fuel/air mixing/combustion data in which we have compared results using the SFM with those using different values of constant turbulent Prandtl and Schmidt numbers.