Rotor wake vortex interaction causes flow separation on the upper surface of a lifting surface at low angles of attack, where the time-averaged flow would be expected to remain fully attached. This phenomenon is studied using a full-scale UH-1 stabilator and a two bladed teetering rotor in a wind tunnel. Several surprising phenomena have emerged. Current prediction methods for tilt-rotor aircraft interactional aerodynamics are likely to miss such phenomena, especially if the rotor wake is time-averaged before interaction. If a time-resolved wake were used, periodic separation and reattachment would be expected, as opposed to the unsteady three-dimensional separation with time-averaged spanwise flow which emerges. The separation is a possible contributor to the observed download on the wing, and a driver of large vibratory airloads on the wings as well as on control surfaces of all rotorcraft. The wing pressure distributions and periodic variations are much more complex than expected. Large excursions of separation points are to be ecpected, forcing vibrations. Another surprise is that no actual collisions of the vortex with the surface are seen, nor are the large pressure spikes typical of such collisions.
Rotor-wake-induced flow separation on a lifting surface
Durch die Rotorblatt-Nachlaufzone induzierte Strömungstrennung auf einer Tragfläche bei Auftriebsbedingungen
Journal of the American Helicopter Society ; 40 , 2 ; 24-27
1995
4 Seiten, 6 Bilder, 5 Quellen
Aufsatz (Zeitschrift)
Englisch
Hubschrauber , Rotor (Drehflügel) , Aerodynamik , Wirbelströmung , Strömungstrennung , dynamischer Auftrieb , Anstellwinkel (Tragflügel) , Zeitverhalten , Windkanal , Versuchsmodell , Druckstoß , Strömungsfeld , Vorhersage , Wechsellast (mechanisch) , Druckverteilung , Druckmessung , Strömungsvisualisierung
Rotor-Wake-Induced Flow Separation on a Lifting Surface
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