High Velocity Jet Noise Source Location and Reduction. Task 6. Supplement. Computer Programs: Engineering Correlation (M*S) Jet Noise Prediction Method and Unified Aeroacoustic Prediction Model (M*G*B) for Nozzles of Arbitary Shape PDF Download
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Author: P. R. Gliebe
Publisher:
ISBN:
Category :
Languages : en
Pages : 215
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This General Supplement Report documents two Computerized Jet Noise Prediction Techniques: the Engineering Method and the Unified Aeroacoustic Prediction Model. A complete description of the computer programs is provided, including examples of input preparation and output cases, plus a listing of the FORTRAN computer code. The comprehensive, empirical, jet noise prediction method has been developed by correlating extensive data from this program and available data from other published sources. The data were correlated by means of basic engineering principles and physical parameters. The resulting prediction method includes unsuppressed conical nozzles; multitube and multichute single- and dual-flow suppressed nozzles; and multitube/multichute nozzles with hardwall and treated sectors. A unified aerodynamic/acoustic prediction technique has also been developed for assessing the noise characteristics of suppressor nozzles. The technique utilizes an extension of Reichardt's method so as to provide predictions of a jet plume flow field. The turbulent fluctuations in the mixing regions of the jet are assumed to be the primary source of noise generation, as in Classical Theories of Jet Noise. The alteration of the generated noise by the jet plume itself as it propagates through the jet to the farfield is modeled utilizing the high-frequency shielding theory based on Lilley's equation. These basic modeling elements have been coupled together in a discrete volume-element formulation. The individual volume elements are assumed to be uncorrelated with each other, so that the total contribution to the farfield is simply the sum of the individual volume element contributions.
Author: P. R. Gliebe
Publisher:
ISBN:
Category :
Languages : en
Pages : 215
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Book Description
This General Supplement Report documents two Computerized Jet Noise Prediction Techniques: the Engineering Method and the Unified Aeroacoustic Prediction Model. A complete description of the computer programs is provided, including examples of input preparation and output cases, plus a listing of the FORTRAN computer code. The comprehensive, empirical, jet noise prediction method has been developed by correlating extensive data from this program and available data from other published sources. The data were correlated by means of basic engineering principles and physical parameters. The resulting prediction method includes unsuppressed conical nozzles; multitube and multichute single- and dual-flow suppressed nozzles; and multitube/multichute nozzles with hardwall and treated sectors. A unified aerodynamic/acoustic prediction technique has also been developed for assessing the noise characteristics of suppressor nozzles. The technique utilizes an extension of Reichardt's method so as to provide predictions of a jet plume flow field. The turbulent fluctuations in the mixing regions of the jet are assumed to be the primary source of noise generation, as in Classical Theories of Jet Noise. The alteration of the generated noise by the jet plume itself as it propagates through the jet to the farfield is modeled utilizing the high-frequency shielding theory based on Lilley's equation. These basic modeling elements have been coupled together in a discrete volume-element formulation. The individual volume elements are assumed to be uncorrelated with each other, so that the total contribution to the farfield is simply the sum of the individual volume element contributions.
Author: P. R. Gliebe
Publisher:
ISBN:
Category :
Languages : en
Pages : 145
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Book Description
A computational procedure is presented for predicting the aerodynamic and acoustic characteristics of jets from nozzles of arbitrary shape. The procedure treats the jet plume as a collection of uncorrelated multipole sound sources which convect with the flow. The aerodynamic characteristics of the jet are evaluated utilizing an extension of Reichardt's theory for free turbulent flows. The acoustic radiation from each of the sound sources is evaluated from high-frequency asymptotic solutions of Lilley's equation. The jet plume is subdivided into several hundred elemental volume sources, each roughly the size of a turbulent eddy volume. The correlated sound level spectra of the individual eddy volumes are summed on a mean-square pressure basis to yield the total turbulent mixing noise levels. An auxiliary calculation of shock-cell broadband noise is made and added to the turbulent mixing noise spectrum to give the total farfield noise. A description of the computational model and associated computer program is presented herein, along with a sample of input and output. A FORTRAN listing of the computer program is also included. (Author).
Author: T. F. Balsa
Publisher:
ISBN:
Category :
Languages : en
Pages : 719
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This report presents the results of Task 2 conducted under the subject program over a period of 45 months. Task 2 was formulated as a fundamental theoretical and experimental study aimed at an understanding of the noise generation and suppression mechanisms of high velocity jets. The mechanisms investigated included changes in turbulence structure, fluid shielding, and alteration of convective amplification of jet noise sources. Several other areas such as physical shielding, shock associated noise, lip noise, effect of fluid/particle additives on jet noise, orderly structure in jets, ejector aeroacoustics, and flight effects on jet noise were also investigated. The most significant achievements of Task 2 were as follows. A unified aeroacoustic theory composed of three ingredients were developed: (1) the prediction of mean properties of the jet plume, (2) deduction of turbulence properties relevant to jet noise by similarity arguments, and (3) the prediction of far-field noise including the effects of fluid shielding. A semiempirical shock noise prediction procedure was also developed. Exhaustive theory-data comparisons for a wide range of nozzle configurations and velocity/temperature combinations were conducted and have confirmed the essential validity of this model as a prediction tool. A comprehensive series of experiments with simple suppressor elements (such as a single rectangular tube, twin jets, linear arrays of jets, circular arrays of jets) was carried out and revealed the importance of acoustic shielding by adjacent jets. A fundamental series of experiments, specifically tailored to reveal fluid shielding as a jet noise suppression mechanism, was successfully conducted.
Author:
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ISBN:
Category : Airplanes
Languages : en
Pages : 572
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Author:
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ISBN:
Category : Jet planes
Languages : en
Pages : 582
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Author:
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ISBN:
Category : Airplanes
Languages : en
Pages : 244
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Author: P. R. Knott
Publisher:
ISBN:
Category :
Languages : en
Pages : 155
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Experimental investigations were conducted of suppression principles; including developing an experimental data base, developing a better understanding of jet noise suppression principles, and formulating empirical methods for the acoustic design of jet noise suppressors. Acoustic scaling has been experimentally demonstrated, and five 'optimum' nozzles have been selected for subsequent anechoic free-jet testing. In-jet/in-jet and in-jet/far-field exhaust noise diagnostic measurements were conducted using a Laser Velocimeter (LV). Measurements were performed on a conical nozzle and a coannular plug nozzle. Two-point, space/time measurements using a two-LV system were completed for the conical nozzle. Measurements of mean velocity, turbulent velocity, eddy convection speed, and turbulent length scale were made for a subsonic ambient jet and for a sonic heated jet. For the coannular plug nozzle, a similar series of two-point, laser-correlation measurements were performed. In addition, cross correlations between the laser axial component of turbulence and a far-field acoustic microphone were performed. This volume is part of the four volume set that constitutes the Task 3 final report. The other volumes are: Volume I-Verification of Suppression Principles and Development of Suppression Prediction Methods, Volume II-Parametric Testing and Source Measurements, Volume III-Suppressor Concepts Optimization. (Author).
Author: J. Brausch
Publisher:
ISBN:
Category :
Languages : en
Pages : 591
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Quantitative and qualitative guidance is provided in selecting noise abatement nozzle designs, applicable to high jet velocity engines and/or supersonic cruise vehicles, to meet specific requirements. The fundamentals of jet noise mechanisms are reviewed, and basic, quantitative, design guide tools are provided. Techniques are presented for estimating suppressor acoustics and aerodynamic performance, mechanical design impact on engine installation, and how various suppressor designs impact aircraft mission in the course of maintaining acceptable sideline and community noise levels. Aerodynamic and acoustic performance and installation penalties may be evaluated based on empirical correlations. Guidelines to minimize exhaust system size consistent with flow and supersonic-expansion requirements and to combine other functional operations with nozzle flow area and expansion control hardware are included. Two independent, acoustic-prediction methods were developed to perform complementary functions. An empirical model, supplemented by guidelines based on experience in designing multielement suppressors, is provided. The model covers a wide range of nozzle geometries and provides quantitative estimates of the acoustic characteristics of a given suppressor nozzle design. A complementary, theoretical, jet-noise-prediction method is more restricted in terms of nozzle geometries which can be properly modeled but provides more details of the aerodynamic flow field and the component acoustic mechanisms. (Author).
Author:
Publisher:
ISBN:
Category : Airplanes
Languages : en
Pages : 676
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Author: C. T. Savell
Publisher:
ISBN:
Category : Jet planes
Languages : en
Pages : 218
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