SBIR-STTR Award

Computational Fluid Dynamics (CFD) is playing a crucial role in the development of the next generation of advanced aerodynamic vehicles, such as the National Aero-Space Plane (NASP). CFD tools are critical to analyze the high Mach number flows typical of these advanced flight vehicles because of limitations on experimental facilities under these extreme flight conditions. However, the validity of CFD codes is limited by their ability to accurately model the complex turbulence processes of high speed flows. Our recent innovations in the development of turbulence transport models based on renormalization group (RNG) methods promise to render many of the most difficult engineering problems of the NASP tractable. Here, we propose to extend and then apply these models to high Mach number wall-bounded compressible flows in which previous modeling efforts have failed. We shall use our HERCULES unstructured grid code as the initial platform for these studies. To expedite access to the new technology for Wright-Patterson personnel, as well as to provide critical feedback to CHI for the commercialization phase, we also propose to implement the new turbulence models in appropriate Air Force software. This work will yield a practical engineering analysis tool for the NASP project.

In Phase II we propose to further develop our near-wall compressible nenormalization group (RNG) model for high Mach number turbulent flows in production CFD code environments. In Phase I we demonstrated that the new near-wall RNG model offers significant advantages over classical wall function based approaches to compressible turbulence. Further analysis will be made of shock-turbulence interaction effects on the character of turbulence production, dissipation, and non-equilibrium strain and relaxation. This work should clarify the experimentally observed time-dependence of large scale flow features in highly deformed compressible flows. The production codes to be enhanced by the new turbulence model will include both structured and unstructured grid codes in order that numerical issues like efficiency, formulation dependence, resolution dependence, and accuracy be delineated. Three codes will be used: SPARK 3D, UTNS (developed by our Phase II partner United Technologies Research Center), and HERCULES/RAMPANT (a modified version of RAMPANT, a code developed by our Phase III partner, Fluent, Inc.). Both intermediate and final versions of SPARK 3D will be delivered to enhance operational Air Force CFD design and analysis capabilities. A comprehensive test matrix, including both prototype and realistic scramjet combustor geometries, will be studied.