caa a22 4500 477093477 CHVBK 20180405111521.0 cr unu---uuuuu 170330e19960501xx s 000 0 eng 10.1007/BF00204633 doi (NATIONALLICENCE)springer-10.1007/BF00204633 Analysis of helicopter blade vortex structure by laser velocimetry [Elektronische Daten] [A. Boutier, J. Lefèvre, F. Micheli] In descent flight, helicopter external noise is mainly generated by the Blade Vortex Interaction (BVI). To under-stand the dynamics of this phenomenon, the vortex must be characterized before its interaction with the blade, which means that its viscous core radius, its strength and its distance to the blade have to be determined by non-intrusive measurement techniques. As part of the HART program (Higher Harmonic Control Aeroacoustic Rotor Test, jointly conducted by US Army, NASA, DLR, DNW and ONERA), a series of tests have been made in the German Dutch Wind Tunnel (DNW) on a helicopter rotor with 2 m long blades, rotating at 1040 rpm; several flight configurations, with an advance ratio of 0.15 and a shaft angle of 5.3°, have been studied with different higher harmonic blade pitch angles superposed on the conventional one (corresponding to the baseline case). The flow on the retreating side has been analyzed with an especially designed 3D laser velocimeter, and, simultaneously, the blade tip attitude has been determined in order to get the blade-vortex miss distance, which is a crucial parameter in the noise reduction. A 3D laser velocimeter, in backscatter mode with a working distance of 5 m, was installed on a platform 9 m high, and flow seeding with submicron incense smoke was achieved in the settling chamber using a remotely controlled displacement device. Acquisition of instantaneous velocity vectors by an IFA 750 yielded mean velocity and turbulence maps across the vortex as well as the vortex position, intensity and viscous radius. The blade tip attitude (altitude, jitter, angle of incidence) was recorded by the TART method (Target Attitude in Real Time) which makes use of a CCD camera on which is formed the image of two retroreflecting targets attached to the blade tip and lighted by a flash lamp. In addition to the mean values of the aforementioned quantities, spectra of their fluctuations have been established up to 8 Hz. Springer-Verlag, 1996 Boutier A. Office National d'Etudes et de Recherches Aérospatiales BP 72, F-92322, Châtillon Cedex, France aut Lefèvre J. Office National d'Etudes et de Recherches Aérospatiales BP 72, F-92322, Châtillon Cedex, France aut Micheli F. Office National d'Etudes et de Recherches Aérospatiales BP 72, F-92322, Châtillon Cedex, France aut Experiments in Fluids Springer-Verlag 21/1(1996-05-01), 33-42 0723-4864 21:1<33 1996 21 348 https://doi.org/10.1007/BF00204633 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00204633 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Boutier A. Office National d'Etudes et de Recherches Aérospatiales BP 72, F-92322, Châtillon Cedex, France aut NATIONALLICENCE 700 1- Lefèvre J. Office National d'Etudes et de Recherches Aérospatiales BP 72, F-92322, Châtillon Cedex, France aut NATIONALLICENCE 700 1- Micheli F. Office National d'Etudes et de Recherches Aérospatiales BP 72, F-92322, Châtillon Cedex, France aut NATIONALLICENCE 773 0- Experiments in Fluids Springer-Verlag 21/1(1996-05-01), 33-42 0723-4864 21:1<33 1996 21 348 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer