F-35 CFD Validation via Infrared Thermography Comparisons Using the Lockheed Martin Falcon CFD Solver

This paper describes recent validation efforts of the Lockheed Martin Aeronautics in-house computational fluid dynamics (CFD) solver Falcon on the F-35 using NASA Ames Unitary Plan Wind Tunnel infrared (IR) thermography imagery. Prior work on the F-35 has demonstrated outstanding experimental match at challenging conditions, using integrated force & moment match and local pressure coefficient comparisons. Across a broad range of conditions, Falcon typically meets (or exceeds) the engineering accuracy requirements, and much of the F-35 detailed aerodynamic design and external aerodynamic analysis has been conducted with the Falcon CFD solver. Falcon continues to be leveraged on the F-35 program, alongside many other legacy and developmental aircraft in the Lockheed Martin portfolio. Infrared thermography has gained interest at Lockheed Martin for the visualization of flow features during wind tunnel (WT) tests. These visualization techniques offer a powerful experimental dataset for the validation of CFD solutions. This work describes efforts undertaken to develop a methodology enabling CFD/IR solution comparison for CFD validation purposes. Several methods of CFD solution visualization techniques were investigated to encourage feature identification and comparison to IR thermography data. Excellent flow feature CFD/WT match is shown at a wide range of flow conditions and external store configurations involving highly complex flowfields. Selected flow regimes are identified for future investigation. Finally, discussion is held on limiting cases where wind tunnel model characterization can confound possible match between CFD solutions and IR visualizations on a subset of complex flow features.