BLADE VORTEX INTERACTION RESEARCH
IN THE 80- By 120-FOOT TUNNEL
Experimentally simulate the aerodynamics and acoustics of parallel (2-D), unsteady helicopter rotor blade-vortex interactions, in a manner closely matching the simplified computational models frequently used for numerical simulations.
A 7-foot diameter, 2-bladed rotor was operated at zero thrust to minimize self-generated vortex interactions. A separate wing tip was used to generate a vortex upstream of the rotor. The vortex strength, rotation, and interaction distance from the blade, as well as the rotor tip speed and advance ratio could all be independently controlled. A wide range of values of these parameters were tested. Blade surface pressures were measured with 60 transducers distributed on both top and bottom surfaces at three radial and 10 chordwise stations. The near acoustic field was measured with two fixed microphones positioned approximately 2-3 blade chords from the interaction position. The acoustic far-field was measured with five microphones mounted in a vertical array on a traverse approximately 3 blade radii to the side of the rotor.
An extensive data base has been obtained consisting of simultaneous measurements of blade pressures and near- and far-field acoustics, as well as vortex characteristics and interaction geometry parameters. Preliminary comparisons with computational results, as well as consistency checks indicate a high-quality data set. Correlation studies are underway in cooperation with several NASA and university researchers. An informal working group is in the process of being formed to evaluate BVI noise prediction capabilities of current codes.
Kitaplioglu, C. and Caradonna, F. X., "A Study of Blade-Vortex Interaction Aeroacoustics Utilizing an Independently Generated Vortex," Presented at AGARD 75th Fluid Dynamics Panel Meeting and Symposium on Aerodynamics and Aeroacoustics of Rotorcraft, Berlin, Germany, October 1994.
Kitaplioglu, C. and Caradonna, F. X. "Aerodynamics and Acoustics of Blade-Vortex Interaction Using An Independently Generated Vortex," Proceedings of the American Helicopter Society Aeromechanics Specialist Conference, San Francisco, CA, January 1994. Paper No. 1.4.
McCluer, M. S., Baeder, J.D, and Kitaplioglu, C., "Comparison of Experimental Blade-Vortex Interaction Noise with Computational Fluid Dynamic Calculations," Proceedings of the 51st Annual Forum of the American Helicopter Society, May 1995.
Point of Contact
NASA Ames Research Center
Moffett Field CA 94035-1000