The Computation And Analysis Of Helicopter Impulsive Noise PDF Download

Are you looking for read ebook online? Search for your book and save it on your Kindle device, PC, phones or tablets. Download The Computation And Analysis Of Helicopter Impulsive Noise PDF full book. Access full book title The Computation And Analysis Of Helicopter Impulsive Noise.

New Computational Methods for the Prediction and Analysis of Helicopter Noise

New Computational Methods for the Prediction and Analysis of Helicopter Noise
Author: Roger C. Strawn
Publisher:
Total Pages: 18
Release: 1996
Genre: Fluid dynamics
ISBN:
GET BOOK

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."

Helicopter Impulsive Noise: Theoretical and Experimental Status

Helicopter Impulsive Noise: Theoretical and Experimental Status
Author: F. H. Schmitz
Publisher:
Total Pages: 110
Release: 1983
Genre:
ISBN:
GET BOOK

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.

An Experimental Study of Helicopter Rotor Impulsive Noise

An Experimental Study of Helicopter Rotor Impulsive Noise
Author: William E. Bausch
Publisher:
Total Pages: 244
Release: 1971
Genre:
ISBN:
GET BOOK

Download An Experimental Study of Helicopter Rotor Impulsive Noise Book in PDF, ePub and Kindle

Results of a study of helicopter rotor impulsive noise (RIN) are presented. Rotor noise, together with rotor blade dynamic and pressure data, was measured during hover and cruise of a CH-53A helicopter for use in a correlation study of calculated and measured noise. In addition, the rotor rotational noise analysis described in U.S. Army Aviation Materiel Laboratories (USAAVLABS) technical Report 70-1B was modified to reduce computation time and to include blade flapping and coning motions. The inclusion of these motions, however, is shown to have little effect on the predicted noise. Correlation of calculated and measured noise harmonic amplitudes is generally within 5 dB through the third harmonic at distances less than 1000 feet in front of the helicopter. Waveform correlation of calculated and measured time histories of acoustic pressure is good. RIN is identified as being primarily a rotational noise phenomenon, ordered at the blade passage frequency and its harmonics, rather than amplitude modulated broadband noise. Hover RIN is shown to be due to vortex interference (blade/wake interaction RIN), while cruise RIN is shown to be due to the combination of acoustic effects of a high subsonic tip Mach number on wave propagation and blade drag, and is referred to as advancing blade RIN.

Comparison of Measured and Calculated Helicopter Rotor Impulsive Noise. [wind Tunnel Test Data and Prediction Analysis Techniques]

Comparison of Measured and Calculated Helicopter Rotor Impulsive Noise. [wind Tunnel Test Data and Prediction Analysis Techniques]
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
Total Pages: 30
Release: 2018-07-26
Genre:
ISBN: 9781724260437
GET BOOK

Download Comparison of Measured and Calculated Helicopter Rotor Impulsive Noise. [wind Tunnel Test Data and Prediction Analysis Techniques] Book in PDF, ePub and Kindle

The thickness noise theory is discussed. Two full-scale rotors were tested in a wind tunnel with several tips involving changes in chord, thickness, and sweep. Impulsive noise data reduction procedures used are described. The calculated and measured impulsive noise peak pressures as a function of advancing tip Mach number are compared, showing good correlation for all rotors considered. Johnson, W. and Lee, A. Ames Research Center NASA-TM-78473, A-7355 NAS2-9399; RTOP 505-10-21

Physical Analysis of the Impulsive Aspects of Helicopter Noise

Physical Analysis of the Impulsive Aspects of Helicopter Noise
Author: William J. Galloway
Publisher:
Total Pages: 394
Release: 1977
Genre:
ISBN:
GET BOOK

Download Physical Analysis of the Impulsive Aspects of Helicopter Noise Book in PDF, ePub and Kindle

An evaluation is made of several helicopter flyover noise calculation schemes intended to describe signal impulsive character. These schemes were proposed by ICAO member organizations. Data are presented for various recorded flyovers and for simulations of helicopter flyovers. (Author).

Helicopter Model Rotor-blade Vortex Interaction Impulsive Noise: Scalability and Parametric Variations

Helicopter Model Rotor-blade Vortex Interaction Impulsive Noise: Scalability and Parametric Variations
Author:
Publisher:
Total Pages: 36
Release: 1984
Genre:
ISBN:
GET BOOK

Download Helicopter Model Rotor-blade Vortex Interaction Impulsive Noise: Scalability and Parametric Variations Book in PDF, ePub and Kindle

Acoustic data taken in the anechoic Deutsch-NIederlaendischer Windkanal (DNW) have documented the blade-vortex interaction (BVI) impulsive noise radiated from 1/7-scale model main rotor of the AH-1 series helicopter. Average model-scale data were compared with averaged full-scale, in-flight acoustic data under similar nondimensional test conditions. At low advance ratios (mu = 0.164-0.194), the data scale remarkably well in level and waveform shape, and also duplicate the directivity pattern of BVI impulsive noise. At moderate advance ratios (mu = 0.224-0.270), the scaling deteriorates, suggesting that the model-scale rotor is not adequately simulating the full-scale BVI noise; presently, no proved explanation of this discrepancy exists. Carefully performed parametric variations over a complete matrix of testing conditions have shown that all of the four governing nondimensional parameters -- tip Mach number at hover, advance ratio, local inflow ratio, and thrust coefficient -- are highly sensitive to BVI noise radiation. Keywords: Helicopter noise; Blade vortex interaction; Measured acoustics.