Owls are commonly known for their quiet flight, enabled by three adaptions of their wings and plumage: leading edge serrations, trailing edge fringes and a soft and elastic downy upper surface of the feathers. In order to gain a better understanding of the aeroacoustic effects of the third property that is equivalent to an increased permeability of the plumage to air, an experimental survey on a set of airfoils made of different porous materials was carried out. Several airfoils with the same shape and size but made of different porous materials characterized by their flow resistivities and one non-porous reference airfoil were subject to the flow in an aeroacoustic open jet wind tunnel. The flow speed has been varied between approximately 25 and 50 m/s. The geometric angle of attack ranged from -16 deg to 20 deg in 4 deg-steps. The results of the aeroacoustic measurements, made with a 56-microphone array positioned out of flow, and of the measurements of lift and drag are given and discussed.
Measurement of the noise generation at the trailing edge of porous airfoils
Messung der Geräuscherzeugung an der Hinterkante von porösen Tragflügeln
Experiments in Fluids ; 48 , 2 ; 291-308
2010
18 Seiten, 19 Bilder, 1 Tabelle, 63 Quellen
Article (Journal)
English
Trailing edge noise generation of porous airfoils
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