Towards the Investigation of Unsteady Control Surface Aerodynamics

Abstract

Fostering the application range of CFD methods towards the simulation of entire flight manoeuvres still is a challenging task. It needs to be ensured that the aerodynamic effects evolving from the deflection of a control surface are properly resolved and that their impact on the overall aerodynamics is accurately predicted. Focussing on control surfaces CFD methods have traditionally been applied to investigate the performance of high-lift systems during take-off and landing. In recent years the interest in applying CFD to questions arising from other control surfaces gradually increased. The performance of a vertical tail with deflected rudder in engine-out conditions, for instance, or the efficiency of ailerons and spoilers are nowadays often determined using CFD. All these applications, however, have in common that they address static control surface deflections only. To close the gap towards manoeuvre flight simulations it is therefore indispensable to take the dynamic motion of a control surface and their transient aerodynamic behaviour into account. Spoilers, for example, are well known to exhibit a strongly nonlinear aerodynamic behaviour with significant time lags. Depending on their deflection rate spoilers may even yield a short-term lift augmentation. The investigation of spoiler aerodynamics is therefore hardly possible with low-fidelity tools. A profound assessment of the transient aerodynamic behaviour of a dynamic spoiler therefore requires an experimental data base with which the higher-fidelity CFD simulations can be validated. As DLR was lacking a wind tunnel model offering these functionalities it was decided to modify the DLR-F15 model with a dynamic control surface. The present paper highlights the constraints for the development of this new version of the DLR-F15 model and gives an overview on the background and the objective of the work planned.