TECHNOLOGY AREAS: Air Platform, Weapons

ACQUISITION PROGRAM: F-35 Joint Strike Fighter Program Office, ACAT ID

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), which controls the export and import of defense-related material and services. Offerors must disclose any proposed use of foreign nationals, their country of origin, and what tasks each would accomplish in the statement of work in accordance with section 3.5.b.(7) of the solicitation.

OBJECTIVE: Develop innovative approaches for a time-accurate computational fluid dynamic (CFD) solution for moving bodies with control surfaces.

DESCRIPTION: CFD can be used to certify a store for safe release from the parent aircraft. In this approach, grids around the aircraft and stores need to be generated. For the past 20 years, the structured overset grid method has been successfully applied to store separation and validated against flight test. The drawback of this method is the excessive time and effort required to generate structured grids and ensure proper interpolations for overset grids. Two to three months are required to generate and assemble structured grids for store separation analysis, which leads to a delay in store certification. There is a strong need to automate or expedite the grid generation process for faster CFD solutions to support test and evaluation in a timely manner. Recently, there have been some efforts to attack moving-body problems with unstructured overset grid and deforming unstructured grid approaches. Compared to structured grids, unstructured grids can be generated quickly. However, the unstructured grid technology is not yet mature enough to be applied to moving body problems. For unstructured overset grid methods, handling the failed interpolation grid points, called "orphan points" is still an issue. On the other hand, large deformation and excessive computational requirements are issues that still need to be resolved for deforming unstructured grid approaches. A possible approach could be the combined use of Cartesian and unstructured overset grids but other innovative solutions will also be considered.

PHASE I: Develop a methodology for moving body simulation based on CFD and demonstrate feasibility by performing simple analysis.

PHASE II: Fully implement the methodology into a usable analysis tool. Perform preliminary validation and verification through analysis and testing

PHASE III: Transition the technology to the DOD weapon community and commercial aerospace industry.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Potential commercial applications include the aerospace industry and the weapon compatibility related aerospace industry.

REFERENCES:
1. Pandya, M. J. and Frink, N. T.: "Agglomeration Multigrid for an Unstructured-Grid Flow Solver," AIAA 2004-0759, January 2004.

2. Pandya, M. J. Frink, N.T., Abdol-Hamid, K.S., and A Chung, J.J.: "Recent Enhancements to USM3D Unstructured Flow Solver for Unsteady Flows", AIAA 2004-5201, August, 2004.

3. Pandya, M.J., Frink, N.T., and Noack, R.W.: "Progress Toward Overset-Grid Moving Body Capability for USM3D Unstructured Flow Solver," AIAA 2005-5118, June 2005.

4. Pandya, M.J., Abdol-Hamid, K.S., Campbell, R.L., and Frink, N.T., "Implementation of Flow Tripping Capability in the USM3D Unstructured Flow Solver," AIAA 2006-0919.

5. YikLoon Lee, Jame D. Baeder, "Implicit Hole Cutting - A New Approach to Overset Grid Connectivity," AIAA 2003-4128, The 16th AIAA Computational Fluid Dynamics Conference, Orlando, June 2003.

6. Nemec, M.N., and Aftosmis, M.J., "Adjoint error estimation and adaptive refinement for embedded-boundary Cartesian meshes,",AIAA Paper 2007-4187.

7. Murman, S.M., and Aftosmis, M.J., AIAA 2007-0074 "Dynamic analysis of atmospheric-entry probes and capsules," AIAA Paper 2007-0074.

KEYWORDS: Store Separation; CFD, Moving Body Simulation; Cartesian Grids, Unstructured Grids; Hole Cutting.

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