Laser-Doppler velocimetry was employed to experimentally investigate two-dimensional airfoil-vortex interaction. Vortices were generated by sinusoidally oscillating a NACA 0012 airfoil about its quarter-chord at a reduced frequency of k=2.05 and an amplitude of +/- 10 deg in angle of attack. The target airfoil, a NACA 632A015 was immersed in the wake, two chord lengths downstream of the vortex generator's trailing edge. Phase-averaged velocity measurements of the flow around the target airfoil were made with the latter at angles of attack of alpha = 0 deg (unloaded blade) and alpha = 10 deg (loaded blade). A close encounter with a counterclockwise rotating vortex was studied for both angles of attack and a head-on collision which splits the counterclockwise rotating vortex in two was investigated for alpha = 10 deg. Vorticity fields were constructed and surface pressure fluctuations on the airfoil were determined. It was found that the most violent interaction occurs when the disturbing vortex passes very near over the loaded airfoil. On the other hand, with head-on collision, the disturbing vortex is split, the pressure spikes are drastically reduced and the vortex desintegrates. The opportunity arises therefore to unload a blade during the short interval of vortex interaction, in order to reduce the severity of blade-vortex interaction.
Parallel blade-vortex interaction
Journal of Fluids and Structures ; 12 , 7 ; 801-838
1998
40 Seiten, 27 Bilder, 52 Quellen
(+ 2S. Bilder)
Aufsatz (Zeitschrift)
Englisch
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