TECHNOLOGY AREAS: Air Platform, Sensors, Weapons

ACQUISITION PROGRAM: PMA-201, PMA-242, PMA-259

OBJECTIVE: Develop and demonstrate viscous modeling methodologies and algorithms applicable to Cartesian-based flow solvers that provide a high degree of automation and adaptive accuracy.

DESCRIPTION: Computational Fluid Dynamics (CFD) tools have become common components of aerodynamic design and development programs. Their usefulness, accuracy and applicability have been repeatedly demonstrated. However, due to significant time, labor and computer resources required for the generation of an aerodynamic database using general CFD methods it is commonplace to employ reduced order aerodynamic prediction tools such as linear potential methods or empirically based engineering tools extensively during a design process. Independent efforts within the Navy, NASA and academia over the last decade have produced tools that are able to provide rapid analytical results for complex vehicle geometries but these tools are limited to inviscid modeling. In the weapons development environment, inviscid modeling tools are of very limited usefulness and a general viscous capability is a requirement.

The focus of this STTR is to generate methodologies and algorithms that will allow viscous modeling capabilities within a Cartesian-based solver. The data structure of Cartesian-based flow solvers contains several features that make them amenable to CFD modeling. First, mesh generation is largely automated with few user parameters. Secondly, octree data structures enable adaptation to flow features by splitting or combining cells. Other features include uniform accuracy, low memory requirements, and the ability to model arbitrarily complex geometries, however, the octree data structure is not well suited for viscous modeling. The goal will be to implement a framework for viscous terms that will couple with existing technology for inviscid flow modeling and will provide a means by which common turbulence models can be easily incorporated into the solver. Innovative methodologies must be applicable to arbitrarily complex static geometrical configurations, address subsonic through high supersonic flow/vehicle speeds, provide for a high degree of automation, and impart the capability for solution based adaptation of viscous-dominated flow regions. The proposed framework should be able to support algebraic, one-equation and two-equation turbulence models as well as laminar flow. Resulting algorithms should be validated by comparing results against a selected set of benchmark experimental or computational cases that are generally applicable to external air vehicle flows. Demonstration of internal flow modeling validation cases applicable to air vehicle flowpath simulation may also be considered.

PHASE I: Develop and demonstrate conceptual methodologies. Efforts may assume that existing technology available for octree-based CFD methods is sufficient for inviscid simulation. Methodologies will be evaluated upon the following criteria; ease of implementation, numerical accuracy, resource requirements (CPU time, memory), generality and robustness when applied to arbitrarily complex geometries.

PHASE II: Develop, implement and demonstrate prototype algorithms based on Phase I research. Fully document the algorithmic formulations and validation data.

PHASE III: Work with the government to integrate the algorithms into a general capability that can be used to support Navy weapons development, acquisition and integration programs. This general capability may be used to generate aerodynamic databases for isolated weapons, generate aerodynamic heating rates for high-speed vehicles, assess flowpath performance for air-breathing vehicles and assess loads on weapons in carriage configurations. A Phase III effort may involve discussions and presentations across DoD to demonstrate the new capabilities.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Computational Fluid Dynamics (CFD) analysis has become quite popular within the private-sector due to affordable large-scale computer systems and demonstrated results across several disciplines. Industries currently making use of CFD technology include, medical research, chemical processing, automobile design, marine design and of course, air-vehicle design which today extends from large aircraft manufactures to small businesses designing and selling unmanned air systems (UAS). All of these industries are possible users of the technology developed under this STTR. Several possibilities exist for transition including direct engagement with contractors supporting DoD acquisition programs, performing research in support of government air vehicle technology development programs, or using resulting program documentation to construct or tailor an application to provide demonstrated analytical capability.

REFERENCES:
1. "A Quadtree-Based Adaptively-Refined Cartesian-Grid Algorithm for Solution of the Euler Equations.", De Zeeuw, Darren L., PhD dissertation, University of Michigan 1993.

2. "An Embedded Boundary Cartesian Grid Scheme for Viscous Flows using a New Viscous Wall Boundary Condition Treatment", AIAA 2004–0581, David D. Marshall and Stephen M. Ruffin School of Aerospace Engineering, Georgia Institute of Technology.

3. "Automated parameter studies using a Cartesian method." Murman, S.M., Aftosmis, M.J., and Nemec, M., AIAA Paper 2004-5076 , Aug. 2004.

KEYWORDS: CFD; Viscous; Turbulence; Cartesian; Adaptive; Modeling

TPOC: (760)939-8213
2nd TPOC: (760)939-0252