Experimental and numerical investigations of unsteady aerodynamic derivatives for transport aircraft configurations.

Kurzfassung

In order to improve the accuracy of the experimental and numerical methods used for the prediction of the dynamic derivatives, systematic investigations have been performed using the new lightweight model DLR F12. A new model support for dynamic tests has been put into service at DNW-NWB, which is not only capable of sinusoidal oscillations but also of arbitrary transient. With the panel method VSAERO quasi-steady motions are calculated and with the DLR-TAU code quasi-steady and unsteady motions are simulated. The quasi steady solutions calculated with VSAERO and TAU reveal very similar results in the damping derivatives. For the cross coupled derivatives the tendency is good. But it is necessary to solve the Euler and Navier-Stokes equations in order to consider viscosity and the influence of the time-dependent flow field. Investigations were done in order to understand the unsteady behaviour in more detail. Using the simple generic models which have NACA0012 sections, basic information about the unsteady flow field behaviour are investigated. The numerical and experimental results with the DLR-F12 geometry have shown that not only the quasi-steady simulation of motion is sufficient to get the complete derivatives. The determination of the unsteady alphadot -and betadot -terms is necessary to describe the dynamic derivatives accurately. In addition the measurements of the steady and unsteady pressure distributions using the pressure taps of the DLR-F12 full configuration are necessary for the validation process. Furthermore it is planned to simulate different configurations to allow the analysis of the influence of individual components of the aircraft.