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Wind tunnel test of a 1:6-scaled half wing model with a full-span droop-nose leading edge

: Adachi, Seiji; Bay, Karlheinz; Brandstätt, Peter; Herget, Wolfgang; Simpson, John

Council of European Aerospace Societies -CEAS-:
Greener Aviation 2016. Clean Sky breakthroughs and worldwide status : October 12th to 14th 2016, Brussels
Brüssel: 3AF, 2016
10 pp. (ID: 216)
Greener Aviation Conference <2016, Brussels>
Conference Paper
Fraunhofer IBP ()

Resume : In work package 2.3.1 "LNC Application Studies for 130-seat Regional A/C" of the Clean Sky GRA LNC project, Fraunhofer proposes a high-lift wing having a leading edge depressed downwards (a.k.a. droop nose) for reducing noise radiated from the leading edge. As opposed to the precedent wing models, the current model has a droop nose extended almost over the entire wing from 18% to 98% span. Good aerodynamic performance (cl max = 2.6 at 15 degree angle of attack) of this model has been estimated in CFD analysis conducted in a full-scale condition. Due to the Reynolds number effect, CFD analysis in a1:6-scaled condition has shown smaller cl max = 2.0, smaller angle of attack and less abrupt stall behavior. The current study aimed to confirm that the same performance expected in the scaled condition is actually observed in a wind tunnel. For this purpose, a 1:6-scaled half wing model was first designed and manufactured so that it can be set in three different configurations: (1) clean wing,(2) high-lift baseline having deployed TE flaps but no droop nose leading edge and (3) full high-lift with droop nose. WT tests with this model were performed in an automotive WT facility in Weissach, Germany. Flow speed was set at 40 m/s. Aerodynamic forces and moments were measured by a six-component balance at various angles of attack ranging from -6 to 20 degrees with 2 degree step. In these tests, the model was placed upright on a platform covering a balancerig raised above the WT floor in order not to disturb the flow. In the tests with a transition tripping strip attached on the suction side near the LE, cl max of 1.0 at AoA of 10 degree for the clean wing, cl max of 1.7 at AoA of 8 degree for the high-lift baseline and cl max of 1.9 at 12 degree angle of attack for the droop-nose configuration. All the configurations have less abruptstall behavior as expected. These results are in good agreement with those of the CFD analysis. In the test without the transition tripping strip, very similar results were observed in the clean wing and high-lift baseline configurations. In the droop nose configuration, however, a large cl max of 2.5 at a very large stall angle of 20 degree was observed during the WT test. This results hould be more investigated. In addition to aerodynamic examination, aeroacoustic noise sources were also examined with an acoustic beamforming system during the WT tests. No noise sources would be detected for the clean wing. For both high-lift configurations, these were found at few points on the leading edge, at the outer flap and at one of the stay supporting the inner flap. No qualitative difference insource distribution could be found between these two configurations.