Flap noise measurements in a closed wind tunnel with a phased array

Flap noise measurements in a closed wind tunnel with a phased array

van de Wal, H.M.M.
Sijtsma, P.

National Aerospace Laboratory NLR

2001-12-31

The effects of winglet type "fences" at the outboard flap tip, and a blunt flap trailing edge on the airframe noise have been measured in a low-speed wind tunnel on a 8.5% half model. Both a single (extending downward) and a double type "fence" configuration (extending upward as well as downward from the wing) have been investigated. An airframe noise reduction up to 7 dB has been found for the flap tip source, which was about equal for the single and double fence configurations. For the blunt trailing edge no significant airframe noise effects were found. Reflections of the sound waves at the wind tunnel walls may cause errors in the measured airframe noise sound powers. Sound absorbing tunnel wall linings may reduce these errors. From measurements with a reference source, it was found that these errors are small for the present test setup and the frequency range of 4 kHz and higher, which was relevant for the present measurements. It was also found that an absorbing tunnel wall has little effect on the measured source strengths, both for the aircraft model and the reference source, which supports the conclusion of small errors due to tunnel wall reflections.

http://resolver.tudelft.nl/uuid:360c5940-ad68-4bec-b92f-cad39371615f

Nationaal Lucht- en Ruimtevaartlaboratorium

Campus only

NLR Technical Publication TP 2001-632

Aerospace Engineering Reports

report

(c)2001 National Aerospace Laboratory NLR