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Abstract
An appraisal is made of several subgrid scale (SGS) viscous/scalar dissipation closures via a priori analysis of direct numerical simulation data in a temporally evolving compressible mixing layer. The effects of the filter width, the compressibility level and the Schmidt number are studied for several models. Based on the scaling of SGS kinetic energy, a new formulation for SGS viscous dissipation is proposed. This yields the best overall prediction of the SGS viscous dissipation within the inertial subrange. An SGS scalar dissipation model based on the proportionality of the turbulent time scale with the scalar mixing time scale also performs the best for the filter widths in the inertial subrange. Two dynamic methods are implemented for the determination of the model coefficients. The one based on the global equilibrium of dissipation and production is shown to be more satisfactory than the conventional dynamic model.
Acknowledgements
This research was sponsored by the National Center for Hypersonic Combined Cycle Propulsion Grant FA-9550-09-1-0611. The technical monitors on the grant are Dr Chiping Li (AFOSR), Dr Aaron Auslender (NASA) and Dr Rick Gaffney (NASA). Computational resources are provided by the Center for Computational Research (CCR) at the State University of New York at Buffalo. We are grateful to Prof. Stephen Pope for his guidance in developing a new closure for SGS viscous dissipation. We are also indebted to Prof. Givi for many helpful discussions.