Numerical Simulation of Manoeuvring Aircraft by Aerodynamic and Flight-Mechanic Coupling

In this paper some of the current results of the "Aerodynamic Simulation of Unsteady Manoeuvres (AeroSUM)" project, of the Institute of Design Aerodynamics at DLR, will be presented. The main focus of the project is the numerical simulation of unsteady manoeuvres of fighter aircraft. The main objective of the simulation is the coupling of aerodynamic and flight-mechanic interactions. The numerical simulation is performed with an unstructured, time accurate Navier-Stokes flow solver, TAU, which has been developed by DLR. For the coupling between the aerodynamics and flight-mechanics, the mechanical-system simulation tool SIMPACK is used, in conjunction with the flow solver. For the validation of the results of the numerical simulation software, comparisons to experimental data will be performed. The experimental data will be obtained from extensive wind-tunnel testing of a generic delta-wing aircraft model. The AeroSUM wind-tunnel model is a cropped-delta-wing configuration consisting of a fuselage and wings with trailing edge flaps. It is specifically designed for testing in the "Transonic Wind-Tunnel Göttingen (TWG)". The experimental set-up is capable of simulating both controlled and free-to-roll manoeuvres, at various angles-of-attack, as well as static flight conditions. In this paper some of the results of three separate flight conditions/manoeuvres will be presented. First of all, several Static Flight results will be presented to show the static flight-mechanic behaviour of the configuration, and the structure of the vortex dominated flow-field due to the angle-of-attack and roll-angle. Results of surface pressure and roll-moment will be shown to compare favourably with the experimental data. The static simulation cases are the starting points for the unsteady simulations. The second test-case is Transient Flight. The aircraft is set in a periodic roll-motion, with a given amplitude in roll-angle and frequency. Results of surface pressure and roll-moment and several roll-angle locations will be shown to have good agreement with the experimental data. Finally we will present results of a coupled simulation, i.e. a free-roll manoeuvre. The aircraft is released from an initial angle-of-attack and roll-angle, and allowed to freely roll into a trim-point where it is stable. Results of surface pressure, roll-moment, and trim-point, for both high and low angles-of-attack, will be shown to have good comparison with the experimental data. The desired manoeuvrability capabilities of fighter aircraft keep increasing, thus the design and development of such aircraft become ever more complex. It is hoped that the use of coupled simulation-packages like TAU-SIMPACK will assist in keeping the complexity of fighter aircraft development at a manageable level for years to come. Therefore, the final aim of the project is the capability to simulate a fully configured, manoeuvring fighter aircraft, i.e. an aircraft with several control-surfaces and thrust-vector devices