Prediction Of Helicopter Rotor Discrete Frequency Noise PDF Download
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Author | : Kenneth S. Brentner |
Publisher | : |
Total Pages | : 106 |
Release | : 1986 |
Genre | : Helicopters |
ISBN | : |
Download Prediction of Helicopter Rotor Discrete Frequency Noise Book in PDF, ePub and Kindle
Author | : Kenneth S. Brentner |
Publisher | : |
Total Pages | : 12 |
Release | : 1987 |
Genre | : |
ISBN | : |
Download A Prediction of Helicopter Rotor Discrete Frequency Noise for Three Scale Models Using a New Acoustics Program Book in PDF, ePub and Kindle
Author | : Jean Prieur |
Publisher | : |
Total Pages | : 117 |
Release | : 1997 |
Genre | : |
ISBN | : |
Download Aeroacoustics of Open Rotors Book in PDF, ePub and Kindle
Author | : |
Publisher | : |
Total Pages | : 104 |
Release | : 1983 |
Genre | : |
ISBN | : |
Download Limits on the Prediction of Helicopter Rotor Noise Using Thickness and Loading Sources: Validation of Helicopter Noise Prediction Techniques Book in PDF, ePub and Kindle
Author | : Robert N. Hosier |
Publisher | : |
Total Pages | : 92 |
Release | : 1974 |
Genre | : Aerodynamic load |
ISBN | : |
Download Helicopter Rotor Rotational Noise Predictions Based on Measured High-frequency Blade Loads Book in PDF, ePub and Kindle
In tests conducted at the Langley helicopter rotor test facility, simultaneous measurements of up to 200 harmonics of the fluctuating aerodynamic blade surface pressures and far-field radiated noise were made on a full-scale nontranslating rotor system. After their characteristics were determined, the measured blade surface pressures were converted to loading coefficients and used in an existing theory to predict the far-field rotational noise. A comparison of the calculated and measured noise shows generally good agreement up to 300 to 600 Hz, depending on the discreteness of the loading spectrum. Specific attention is given to the effects of the blade loading coefficients, chordwise loading distributions, blade loading phases, and observer azimuthal position on the calculations.
Author | : F. H. Schmitz |
Publisher | : |
Total Pages | : 110 |
Release | : 1983 |
Genre | : |
ISBN | : |
Download Helicopter Impulsive Noise: Theoretical and Experimental Status Book in PDF, ePub and Kindle
The theoretical and experimental status of helicopter impulsive noise is reviewed. The two major source mechanisms of helicopter impulsive noise are addressed: high-speed impulsive noise and blade-vortex interaction impulsive noise. A thorough physical explanation of both generating mechanisms is presented together with model and full-scale measurements of the phenomena. Current theoretical prediction methods are compared with experimental findings of isolated rotor tests. The noise generating mechanisms of high speed impulsive noise are fairly well understood - theory and experiment compare nicely over Mach number ranges typical of today's helicopters. For the case of blade-vortex interaction noise, understanding of noise generating mechanisms and theoretical comparison with experiment are less satisfactory. Several methods for improving theory-experiment are suggested.
Author | : National Aeronautics and Space Administration (NASA) |
Publisher | : Createspace Independent Publishing Platform |
Total Pages | : 40 |
Release | : 2018-07-10 |
Genre | : |
ISBN | : 9781722498092 |
Download Prediction of XV-15 Tilt Rotor Discrete Frequency Aeroacoustic Noise with Wopwop Book in PDF, ePub and Kindle
The results, methodology, and conclusions of noise prediction calculations carried out to study several possible discrete frequency harmonic noise mechanisms of the XV-15 Tilt Rotor Aircraft in hover and helicopter mode forward flight are presented. The mechanisms studied were thickness and loading noise. In particular, the loading noise caused by flow separation and the fountain/ground plane effect were predicted with calculations made using WOPWOP, a noise prediction program developed by NASA Langley. The methodology was to model the geometry and aerodynamics of the XV-15 rotor blades in hover and steady level flight and then create corresponding FORTRAN subroutines which were used an input for WOPWOP. The models are described and the simplifying assumptions made in creating them are evaluated, and the results of the computations are presented. The computations lead to the following conclusions: The fountain/ground plane effect is an important source of aerodynamic noise for the XV-15 in hover. Unsteady flow separation from the airfoil passing through the fountain at high angles of attack significantly affects the predicted sound spectra and may be an important noise mechanism for the XV-15 in hover mode. The various models developed did not predict the sound spectra in helicopter forward flight. The experimental spectra indicate the presence of blade vortex interactions which were not modeled in these calculations. A need for further study and development of more accurate aerodynamic models, including unsteady stall in hover and blade vortex interactions in forward flight. Coffen, Charles D. and George, Albert R. Unspecified Center NAG2-554...
Author | : |
Publisher | : |
Total Pages | : 100 |
Release | : 1979 |
Genre | : |
ISBN | : |
Download A Summary and Evaluation of Semi-empirical Methods for the Prediction of Helicopter Rotor Noise Book in PDF, ePub and Kindle
Author | : Roger C. Strawn |
Publisher | : |
Total Pages | : 18 |
Release | : 1996 |
Genre | : Fluid dynamics |
ISBN | : |
Download New Computational Methods for the Prediction and Analysis of Helicopter Noise Book in PDF, ePub and Kindle
Abstract: "This paper describes several new methods to predict and analyze rotorcraft noise. These methods are: 1) a combined computational fluid dynamics and Kirchhoff scheme for far-field noise predictions, 2) parallel computer implementation of the Kirchhoff integrations, 3) audio and visual rendering of the computed acoustic predictions over large far-field regions, and 4) acoustic tracebacks to the Kirchhoff surface to pinpoint the sources of the rotor noise. The paper describes each method and presents sample results for three test cases. The first case consists of in-plane high-speed impulsive noise and the other two cases show idealized parallel and oblique blade-vortex interactions. The computed results show good agreement with available experimental data but convey much more information about the far-field noise propagation. When taken together, these new analysis methods exploit the power of new computer technologies and offer the potential to significantly improve our prediction and understanding of rotorcraft noise."
Author | : |
Publisher | : |
Total Pages | : 84 |
Release | : 1981 |
Genre | : |
ISBN | : |
Download Validation of Helicopter Noise Prediction Techniques Book in PDF, ePub and Kindle