High-Lift Challenges of high performances wing
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One of the key-elements for high performance aircraft design is to design a high lift system within the given spatial constraints without having to increase the wing area to e.g. meet landing speed requirements or, vice versa allow to have a lower wing area, and therefore less wing weight and less drag. Recently and especially in the UP-WING project, very high aspect ratio wings have been designed to increase the aerodynamic performance. In addition to a careful aerodynamics and structural design due to the high flexibility of a high aspect ratio wing, the wing tip chord will be very short and can be easily subject to stall, especially at take-off conditions. However, wing tip stall has to be avoided since often it is not symmetric causing roll instability and is in addition coupled with loss of aileron effectiveness that will be in the wake of the area of separated flow. First starting from a baseline cruise wing configuration, and taking into account all design objective and constrains, the high-lift system has been designed. Neverthless, taking into account the short wing tip chord, solutions to avoid wing tip stall are required. Multifunctional vortex generators have been selected as solutions to avoind wing tip stall. They will have a dual use, will be used as conventional vortex generators to avoid wing tip stall in low speed conditions, but will also be used as load alleviation devices in high speed conditions. For this reason, the Vortex generators will be equipped with actuators that will allow for the vortex generators to be deployed, rotated or retracted so that they can be activated in the optimal conditions for specific flight conditions, but can also be retracted to avoid drag increase in flight conditions where they are not needed. In parallel also flow separation sensors will be developed so that a better knowledge of local flow conditions will support a better control of the vortex generators.
