High Velocity Jet Noise Source Location and Reduction. Task 2 Supplement. Computer Program for Calculating the Aeroacoustic Characteristics of Jets Form Nozzles of Arbitrary Shape PDF Download
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Author: P. R. Gliebe
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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: 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:
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Category : Computer programming
Languages : en
Pages : 304
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Author:
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Category :
Languages : en
Pages : 940
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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.
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Category : Science
Languages : en
Pages : 882
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Category : Airplanes
Languages : en
Pages : 244
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ISBN:
Category : Airplanes
Languages : en
Pages : 572
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ISBN:
Category : Airplanes
Languages : en
Pages : 676
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Category : Jet planes
Languages : en
Pages : 582
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Author:
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ISBN:
Category : Airplanes
Languages : en
Pages : 568
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Book Description
This report presents the results of Task 4 as conducted under the subject program over a period of 30 months. Task 4 was formulated to identify and evaluate several inflight simulation techniques, select the most promising technique for demonstration and validation, and employ that technique in testing under Task 5 of the program. Techniques evaluated include closed-circuit wind tunnels, free jets, rocket sleds, and high speed trains. Pertinent results from the evaluation phase and rationale which led to selection of the free jet simulation technique are discussed, including advantages and disadvantages. The results of a theoretical study aimed at relating the noise signature obtained in a free jet facility for simulation of forward flight effects on jet noise with the noise signature in true flight are presented. Transformation is carried out by extracting 'static directivity' of the noise after correcting for refraction, turbulent scattering, and absorption effects, and then employing a suitable multipole source decomposition to evaluate the proper dynamic effect. A flowchart describing the details of the transformation procedure and a listing of the computer program are included. Acoustic results from the Learjet and NASA-Lewis F-106 Aircraft Flyovers and the French Aerotrain Tests, taken with a baseline, 8-lobe, and 104-tube nozzle were used to formulate a data base for verification of the free jet simulation technique. Detailed directivity and spectra comparisons between aerotrain data and transformed free jet data are presented for three primary jet velocities and two flight velocities for the three nozzle types.
