Experimental and numerical determination of dynamic derivatives of aircraft configuration.

Abstract

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 manoeuvres (as has been demonstrated at the end of 2004 with a X-31 wind tunnel model). With the panel method VSAERO quasi-steady motions are calculated and with the DLR-TAU code quasi-steady and unsteady motions are simulated. The results obtained with the panel method match well with the present measurements. 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 profiles, basic information about the unsteady flow field behaviour are investigated. The numerical and experimental results 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 are necessary to describe the dynamic derivatives accurately In addition the measurement of the unsteady pressure distributions using the pressure taps of the DLR-F12 full configuration which will be performed in a future test campaigns are needed to validate the DLR-TAU Code accurately.