SBIR-STTR Award

Our Phase I program will extend and validate a high-speed engineering transitional model (ETM) using new CUBRC data sets (such as HIFIRE-1) of interest to the Air Force. The ETM is responsive to tunnel noise and wall heating, and predicts the overshoot in heat transfer observed in transitional data. The model solves PDEs for transition onset as well as for an intermittency parameter that blends the viscosity from laminar to turbulent levels. The ETM has full 3D capabilities, viz., the PDEs solved generate a swept onset curve and variable transitional lengths downstream of the onset curve, and it is incorporated into Navier-Stokes codes in a manner akin to the inclusion of 2-equation turbulence models. Validation using fundamental high-speed data sets has been limited to axisymmetric or planar geometries. In this program, ETM predictions will be compared with those of the STABL parabolized stability (PSE) code to examine differences in their onset predictions emphasizing tunnel noise and surface temperature effects. Studies using the ETM will be performed for several basic 3D flows and modeling refinements will be incorporated to improve overall performance. Phase II experimental planning will be performed in collaboration with Holden / CUBRC to support ETM model improvements. BENEFIT

Keywords:
Hypersonics, Transition Onset, Intermittency, Engineering Transition Model (Etm), Parabolized Stability Equations (Pse)

Our Phase II program concentrates on extending, rectifying, and validating the ETM engineering transition model for 3D flows. ETM solves PDE’s for both transition onset and intermittency and has full 3D capabilities, shown to generate swept onset curves and variable transitional lengths downstream of the onset curve. It is incorporated into Navier-Stokes codes in a manner akin to the inclusion of 2-equation turbulence models. Previous efforts validated the ETM using fundamental axisymmetric data sets. This program will concentrate on high-speed (as well as subsonic) 3D flows using published measurements, as well as those from the CUBRC high-speed facilities. Experiments will concentrate on quantifying tunnel noise levels as well as on capturing boundary layer stability characteristics using innovative hot-wire measurement techniques. Results will be used to rectify and validate the 3D ETM, while also benefiting future 3D stability-based model development. All numerical and experimental datasets will be archived in the CRAVE web-based, GUI-driven CFD validation database for access by other users to perform their own validation studies. Finally, modules incorporating the ETM will be developed for use in other structured or unstructured CFD solvers.

Benefit:
Commercialization will result from additional licenses for our CFD codes that will now have a validated “engineering-oriented” model that can predict transitional processes for complex 3D flowfields. Having this unique capability permits CRAFT Tech to obtain additional system and design support work for problems where transition plays a major role. CUBRC should also gain additional experimental support having tunnels with noise levels quantified. The CRAVE validation tool is being commercialized and licensed to varied research facilities and having validation sets included will greatly enhance its utility. Unique to CRAVE is the inclusion of both data as well the CFD solutions, synchronized via specialized scripts, so that external users can try out their codes on varied data sets and compare results with existing CFD solutions in an automated “black-box” manner. The modules developed that solve the ETM equations working with other CFD codes are also a very viable commercial product. The use of CUBRC data sets to firmly establish transitional modeling capabilities in an engineering-oriented code should lead to additional experimental programs for them in the transitional arena. In addition, having their data included in CRAVE is good publicity for CUBRC.

Keywords:
Hypersonics, Transition Onset, Intermittency, Engineering Transition Model (Etm), Parabolized Stabil