Simulation of flight maneuvers in a wind-tunnel

Already at moderate angles of attack small changes in the flight conditions of a delta-wing aircraft can strongly influence the vortex dominated flow field about the wings and thus result in large changes of the aerodynamic loads. Classical approaches for obtaining dynamic stability information as, for example, static and dynamic stability derivatives, are no longer sufficient in developing aircrafts and more and more complex approaches and alternative modeling techniques have been developed. At DLR a numerical simulation framework is under development for calculating a freely flying maneuvering delta-wing aircraft. In this not only the fluid mechanical equations are solved but also, simultaneously, the equations of flight mechanics and aeroelastics. In order to obtain a data base for validating the simulation framework complex maneuvers of an aircraft have been performed in a wind tunnel. Maneuvers have been simulated in the open test section of the 2.85 X 3.20 m2 low-speed atmospheric wind tunnel NWB of the German-Dutch Wind Tunnels DNW. A fully equipped wind tunnel model of the X-31 was designed and built to a scale of about 1:7.25. The model is equipped with eight remotely controlled control surfaces that are moved by eight servo motors. Dynamic surface pressures have been measured by miniature piezo-resistive pressure sensors located at 60% and 70% chord length on the upper surface of the delta wing and on the leading edge flaps. Forces and moments were obtained by a 6-component strain gauge also included in the main part of the model. In the wind tunnel a newly installed test rig with six degrees of freedom was used for the first time for moving the model. The complex three-dimensional motion of the model is controlled by an optical position tracking system. In addition to pitching, rolling and yawing motions also real flight maneuvers were simulated.