LES Studies of Scalar Fluctuations at High Convective Mach Numbers

Abstract : A need has arisen for the development of RANS models for the prediction of scalar fluctuations and turbulent transport in the high speed flow regime. These models will have application, for example, in scramjet combustors and missile exhaust plume signature analyses and other important areas. However, in the high speed flow regime, experimentally derived scalar fluctuation validation data is not readily available due to the inability of relevant experimental measurement techniques (e.g. hot wires) to cope with this flowfield environment. Consequently, model development in this flow regime is difficult. To address this issue, a two part program has been initiated to fill the data gap and thus facilitate model development. Part I of this program involves the collection of LES data over a wide range of conditions. Part II involves the use of these data to evaluate and develop RANS tools to improve predictive capabilities. This paper presents results and preliminary finding of Part I of this program; the collection of LES data regarding scalar transport in planar shear layers. The findings of this study elucidate the effects of compressibility on the character of mean scalar profiles, variations in turbulent Prandtl number, and on scalar rms fluctuations.