UP Wing – Ultra Performance Wing (EU funded project)
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The airplane is the most efficient means of transporting passengers over long distances. In view of man-made global warming, however, it is imperative that air travel also makes its contribution to reducing climate-impacting emissions - the goal is to fly in a climate-neutral manner. In the EU's Clean Aviation funding program, which was launched at the beginning of 2023, this goal is being pursued in a series of projects that build on each other.
One of these, the UP Wing (Ultra Performant Wing) project, is concerned with increasing the efficiency of transport aircraft through novel wing concepts.
One way to reduce an aircraft's fuel consumption is to increase wing aspect ratio, i. e. the ratio of wing span to wing chord. Slender wings have less drag than those with a stocky wing shape. In nature, this can be seen, for example, in the slender wings of an albatross, which is almost continuously in the air at high speed. In technical applications, slender wings are found on wind turbines and gliders, in both cases good aerodynamic efficiency is essential for operation.
The wing aspect ratio of each new development has also increased continuously in commercial aircraft. While the Airbus A300 from 1970 had an aspect ratio of 7.7, the A350 from 2013 has an aspect ratio of 9.3.
Unfortunately, a wing cannot be built as slender as desired. The wing mass increases with the span. The high-lift system is more difficult to integrate into a wing with a low wing chord, and the same applies to the landing gear. In addition, a number of aeroelastic issues arise that can limit the aspect ratio of a wing. The Institute of Aeroelasticity is working on solutions in the UP Wing project.
Although high aspect ratio wings have low induced drag, a number of aeroelastic issues arise, as already mentioned. High aspect ratio wings are relatively soft in bending and torsion, so there is a risk of low rudder effectiveness at high airspeeds and a large influence of wing bending on flight mechanics can be observed. In addition, these structural dynamic properties of the wing can also lead to a reduction in flutter speed, limiting the usable airspeed range.
Which wing aspect ratio offers the best compromise between good aerodynamic performance, low wing mass and good aeroelastic properties? The answer is agiven in UP Wing with the help of numerical studies on the DLR F25 configuration, which was originally developed in the Lufo VI project VirenFrei.
The higher the aspect ratio, and thus the span, the heavier a wing usually becomes. The forces that occur, e.g. the lift, are relevant for the sizing of the wing structure. In order to be able to realize a higher aspect ratio, these forces, the so-called loads, must be reduced. This can be done with passive measures, such as the use of composite materials with specially optimized, unconventional composite materials in the design of the wings, or with active measures, such as the use of control surfaces to reduce gust or maneuver loads.
In the UP Wing project, the Institute of Aeroelasticity is working with the project partners on the development of such procedures and their validation in a wind tunnel test. In the test, an elastic wing based on the DLR F25 configuration will be investigated at a scale of approximately 1:30 in the transonic wind tunnel of DNW in Amsterdam. The Institute of Aeroelasticity participates in the design of the wing model, designs the structure of the wing, and performs CFD analyses of the aerodynamics on the elastic wing. These are then provided to the teams that design the load control algorithms. Furthermore, the Institute of Aeroelasticity will perform the structural dynamics identification prior to the wind tunnel test as well as the extensive measurement data acquisition in the wind tunnel. Load control laws are designed by the DLR Institute of System Dynamics and Control (Oberpfaffenhofen).
Partners in the above described work (wind tunnel tests as well as numerical analyses) are the DLR Institute of System Dynamics and Control (Oberpfaffenhofen) and the DLR Institute of Aerodynamics and Flow Technology (Braunschweig), the Virtual Product House of DLR (Bremen), the European aeronautics research institutions NLR (NL) and ONERA (F), the universities TU Berlin (D) and TU Delft (NL), as well as the industrial partners Airbus (D, F) and Dassault Aviation (F).
In other work packages of the UP Wing project, DLR institutes are working with numerous European partners from research and industry to investigate other specific aspects of the high aspect ratio wing, such as the integration of high-lift devices into the wings or the development of special structural components for use on very slender wings.
This project has received co-funding from the Clean Aviation Joint Undertaking (JU) under grant agreement No 101101974 (project UP Wing). The JU receives support from the European Union’s Horizon Europe research and innovation programme and the Clean Aviation JU members other than the Union.
Clean Aviation
EU
