Smart Droop Nose for application to Laminar Wing of future Green Regional A/C
The Fraunhofer smart droop nose concept is a high lift device technology for future green regional aircraft that provides both aerodynamic and aero-acoustic efficiency. This device generates the required additional high lift in take-o and landing procedures, while maintaining a low noise characteristic. These desirable properties are achieved by using a deformable leading edge without gaps. The two dimensional geometry definition and optimization was carried out in an interactive two-dimensional fluid simulator. Interactivity is achieved by leveraging simplified algorithms and massively parallel graphics processors to significantly speed up the simulation. This in turn provides instant feedback of the aerodynamic properties and allows for an interactive geometry manipulation and optimization. For the input geometry, cross sections of an existing 3D-wing were computed and approximated by cubic B-Splines. These curves naturally preserve C2- continuity of the shape, which is important for good aerodynamic properties. A rotational deformation of the nose tip was applied during the aerodynamic optimization. The resultant shapes were reintegrated in the 3D geometry and combined by a lofting operation leading to an aerodynamically optimized design. During conceptual mechanical design, several kinematics concepts for actuation of the de- formable leading edge were considered. These concepts aimed at reproducing the aerodynamically optimized geometry. For an assessment of the chosen droop nose concept 2D-CFD and CAA simulations were performed in comparison to other wing configurations confirming the aerodynamic and acoustic benefit obtained by this concept. Aerodynamic and aero-acoustic effectiveness of the Fraunhofer droop nose concept were further validated in 3D wind-tunnel tests in model scale. To this end, several WT-models were designed, manufactured, and tested with respect to their lift and drag coefficients as well as noise emission. The models' actuation mechanisms were simplified due to the limited space within the scaled leading edge. Comparisons with 3D-CFD simulation based on a Reynolds-averaged Navier-Stokes turbulence model were performed with reasonable agreement to the measured configurations. Low-noise characteristics of the droop nose were also supported in pseudo-3D CAA analysis. Finally, the paper reports about a droop nose demonstrator that has been designed and will be manufactured for full scale functional tests. The 3m L/E-section features a composite skin and contains the actuation mechanism as well as an ice-protection technology based on nanomaterials. In parallel, a full wing in scale 1:6 equipped with a full span droop nose and a single slotted ap will be produced and examined for its aerodynamic properties in a larger wind tunnel.