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Record Details

Record 70 of 1047
Geometrical acoustics and transonic helicopter sound
Author and Affiliation:
Isom, Morris(New York, Polytechnic University, Brooklyn, United States)
Purcell, Timothy W.(Polytechnic Univ., Brooklyn, NY, United States)
Strawn, Roger C.(NASA Ames Research Center, U.S. Army, Aeroflightdynamics Directorate, Moffett Field)
Abstract: A new method is presented for predicting the impulsive noise generated by a transonic rotor blade. The method is a combined approach involving computational fluid dynamics and geometrical acoustics. A full-potential finite-difference method is used to obtain the pressure field close to the blade. A Kirchhoff integral formulation is then used to extend these finite-difference results into the far field. This Kirchhoff formula is based on geometrical acoustics approximations. It requires initial data across a plane at the sonic radius in a blade-fixed coordinate system. This data is provided by the finite-difference solution. Acoustic pressure predictions show good agreement with hover experimental data for cases with hover tip Mach numbers of 0.88 through 0.96. The cases above 0.92 tip Mach number are dominated by non-linear transonic effects seen as strong shocks on and off the blade tip. This paper gives the first successful predictions of far-field acoustic pressures for high-speed impulsive noise over a range of Mach numbers after delocalization.
Publication Date: Oct 01, 1987
Document ID:
19880032962
(Acquired Nov 28, 1995)
Accession Number: 88A20189
Subject Category: ACOUSTICS
Report/Patent Number: AIAA PAPER 87-2748
Document Type: Preprint
Publisher Information: United States
Financial Sponsor: NASA; United States
Organization Source: Polytechnic Univ.; Brooklyn, NY, United States
NASA Ames Research Center; Moffett Field, CA, United States
Army Aviation Systems Command; Moffett Field, CA, United States
Description: 13p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright
NASA Terms: AEROACOUSTICS; AIRCRAFT NOISE; GEOMETRICAL ACOUSTICS; HELICOPTER PERFORMANCE; ROTARY WINGS; COMPUTATIONAL FLUID DYNAMICS; FINITE DIFFERENCE THEORY; KIRCHHOFF LAW; MACH NUMBER; PRESSURE DISTRIBUTION; TRANSONIC FLOW
Imprint And Other Notes: AIAA, Aeroacoustics Conference, 11th, Sunnyvale, CA, Oct. 19-21, 1987. 13 p.
Availability Source: Other Sources
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