Measurements are presented of the flow produced by the perpendicular encounter between a streamwise vortex and a wing tip. The resulting flow field, which contains two interacting tip vortices, models the turbulence found in the near tip region on the advancing side of a helicopter rotor. This region is a significant source of BWI noise (blade-wake interaction) at level flight and mild climb conditions. Both single and two-point turbulence measurements are presented. The single-point measurements reveal the form of the turbulence structure generated by the interaction of the tip vortices. The two-point measurements reveal, in terms of wavenumber-frequency spectra, the turbulence length scales that would be encountered by a noise-generating blade cutting this flow. It is concluded that the interaction between the vortices not only winds up the wakes to which they are attached but is also a source of new organized turbulence. It is also found that wavenumber-frequency spectra measured in this flow are dominated by the large-eddies present in the turbulence and are not well modeled by assuming a homogeneous isotropic spectrum.
Turbulence structure resulting from a vortex/wing-tip encounter
Untersuchung der durch Rotorblattspitzen-Wirbel-Interaktionen erzeugten turbulenten Strukturen
Journal of the American Helicopter Society ; 44 , 2 ; 141-149
1999
9 Seiten, 14 Bilder, 1 Tabelle, 22 Quellen
Article (Journal)
English
Turbulent Strueture Resulting from a Vortex-Wing-Tip Encounter
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