Flow Analysis of the F-16XL Aircraft (CAWAPI-2) At Transonic Flow Conditions

Abstract

In the framework of the Cranked-Arrow Wing Aerodynamics Project International 2 (CAWAPI-2), a cooperation between Cassidian/EADS (Germany), KTH (Sweden), Lockheed-Martin (USA), NASA Langley (USA) and National Aerospace Laboratory NLR (The Netherlands) to further assess Computational Fluid Dynamics codes against F-16XL flight test data, National Aerospace Laboratory NLR performed an analysis of a set of transonic flight conditions available in the CAWAP database. Flight condition FC70 was used previously during the Cranked-Arrow Wing Aerodynamics Project International to investigate transonic flow on the F-16XL aircraft. During this project it was discovered that flight condition FC70 was flown with a deflected leading edge flap. To facilitate CFD analysis a transonic flight condition without deflected control surfaces was judged desirable by the CAWAPI-2 members. Therefore, it was decided to search the CAWAP database for a transonic flight condition without any control surface deflections. Since no information on the control surface deflections of the other transonic flight conditions was available to the CAWAPI-2 partners, an alternative approach to scrutinize the available flight test sectional surface pressure measurements for indications of control surface deflections was adopted. This analysis revealed that flight condition FC79 was the most likely transonic flight condition to be flown without any control surface deflections. Flight conditions FC70 and FC79 were analyzed using NLR’s in-house developed flow simulation system ENFLOW. Comparison of the measured and simulated surface pressure coefficients confirmed that flight condition FC79 was flown without any control surface deflections, and that this flight condition thus is much better suited for further comparisons between flight test data and CFD simulations.