Hybrid Grid Solutions on the (CAWAPI) F-16XL Using Falcon v4

Abstract

As part of the Cranked Wing Aerodynamics Project International (CAWAPI), computational fluid dynamics (CFD) simulations were performed on the F-16XL geometry at high-lift and transonic flight conditions. This was part of a larger effort by several institutions and companies to try to characterize the relevant flow physics and to compare the results to flight test data. The work summarized in this report used the Lockheed Martin Aeronautics Company proprietary CFD flow solver Falcon v4, which is a general purpose Navier-Stokes flow solver which uses hybrid unstructured computational meshes. The computational mesh used in these studies consisted of prismatic and hexahedral cells near the solid surfaces, tetrahedral cells in the far field, and pyramidal cells transitioning between hexahedral and tetrahedral cells. This mesh was obtained from the UT SimCenter and was generated using Gridgen for the inviscid mesh and proprietary software to generate the viscous prismatic layers. The results on a set of test cases selected by the CAWAPI working group shows good agreement with the flight test data and consistency with the other computational results for the high-lift cases, with the exception of the leading edge suction peak. The key flow features of these types of configurations, including the primary vortex originating on the inboard leading edge of the wings, the secondary vortex on the aft portion of the wing next to the primary vortex, and the vortices shed from the wingtip missile fins are all adequately resolved. The transonic flight test case, which has caused some difficulty because of the nonlinear nature of the flow physics, did not match flight test data as well. This is probably due to a leading edge flap that was deployed during the flight test but which the computational geometry did not reflect. A brief description of the simulations performed is presented below, a description of the Falcon v4 CFD solver is presented, and a summary of the results is presented and explained.