Aerodynamic interactions between the rotor and the airframe of a rotorcraft can have severe effects and are difficult to predict analytically. To attack this problem, the velocity field of a simple rotor-airframe configuration in a wind tunnel has been measured. A pressure-instrumented circular cylinder with a hemispherical nose is used as the airframe model, with a two-bladed teetering rotor suspended above it. The data were shown to be free of tunnel wall effects. The periodic and time-averaged velocity fields were meeasured using a laser velocimeter in planes parallel to and both above and below the rotor tip path plane at advance ratios of 0.1 and 0.15 and a rotor tip Mach number of 0.29. Variations along horizontal lines above the airframe surface also were measured. For the geometry studied, airframe influence on the rotor flow field was mostly confined to the front half of the rotor disc. Hub effects were noticeable, even with the minimal hub dimensions used. The wake geometry agreed well with predictions for an isolated rotor, except for distortions near the airframe. Strong vortex interaction effects were observed. However, most of the observed phenomena can be explained by resort to visualization of vortex dynamics. The configuration appears to be amenable to analytical prediction.
The velocity field of a lifting rotor in low-speed forward flight
Geschwindigkeitsfeld eines Rotors im langsamen Vorwaertsflug
AIAA-Papers ; Jan ; 1-10
1988
10 Seiten, 17 Bilder, 19 Quellen
Conference paper
English