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Unformatted text preview: 1 COMPARISON OF FULL-SCALE XV-15 BLADE-VORTEX INTERACTION NOISE CALCULATIONS WITH WIND TUNNEL DATA Cahit Kitaplioglu and Wayne Johnson Army/NASA Rotorcraft Division NASA Ames Research Center Moffett Field, California Results from the TRAC acoustic prediction system were correlated with data from a test of an isolated full-scale XV-15 rotor in the NASA Ames 80- by 120-Foot Wind Tunnel. The airloads calculation provided by the original CAMRAD.Mod1 code in the standard TRAC system was exercised with several high resolution options, including the FPXBVI CFD code. In addition, the more recent CAMRAD II code was run in place of the original CAMRAD.Mod1. The CAMRAD II code, with a multiple trailer wake model yielding airloads at 3 degree azimuthal resolution, provided excellent correlation with measured BVI pulse amplitude, but less so for pulsewidth. There is indication that better results may be obtained with higher resolution airloads. Notation . c speed of sound C T rotor thrust coefficient (shaft axes) M tip blade tip Mach number r/R microphone radial distance from hub r inner blade root cutout radius R blade radius α s rotor shaft angle (positive aft) β ,β 1c ,β 1s blade flap components φ microphone elevation angle (positive down from rotor plane) μ advance ratio ρ air density σ rotor solidity θ ,θ 1c ,θ 1s blade pitch components ψ azimuth angle (positive conterclockwise from downstream) ____________ . Presented at the American Helicopter Society International Technical Spet Meeting On Aerodynamics, Acoustics, and Test and Evaluation, San Francisco, CA, January 23-25, 2002. Copyright © 2002 by the American Helicopter Society International, Inc. All rights reserved. Introduction Noise, particularly the impulsive type due to blade- vortex interactions (BVI), is a major determinant of the economic and military viability of all rotorcraft. The alleviation of noise has been a focus of substantial research and development efforts by NASA and U.S. rotorcraft industry in recent years. One aspect of this effort has been the intensive work undertaken to create a comprehensive prediction system to compute rotorcraft noise. The culmination of this work, if successful, would create a design tool of obvious value to the development of next generation rotorcraft. Significant progress has been made in recent years in improving the predictive ability of purely computational techniques in calculating rotorcraft noise. Among several approaches, the Tilt-Rotor Aeroacoustic Code (TRAC) system (Ref. 1) was developed cooperatively by NASA and industry participants, specifically focused on prediction of the noise field of tilt-rotor aircraft. The objective of the present work was to determine the extent to which the TRAC system could predict the noise field of a full-scale XV-15 aircraft, as measured during a test in the NASA Ames 80- by 120-Foot Wind Tunnel....
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This note was uploaded on 01/05/2011 for the course DU 3 taught by Professor Frando during the Spring '10 term at University of Dundee.
- Spring '10