On the Prediction of the Near Field Noise of Supersonic Jets PDF Download
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Author: J. B. Ollerhead
Publisher:
ISBN:
Category : Noise
Languages : en
Pages : 116
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Book Description
Author: J. B. Ollerhead
Publisher:
ISBN:
Category : Noise
Languages : en
Pages : 116
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Book Description
Author: Lockheed-Georgia Company
Publisher:
ISBN:
Category : Jet planes
Languages : en
Pages : 156
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Book Description
Author: Andrew Thomas Merck
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The development of a high-speed jet noise prediction method that is significantly less computationally expensive than previous computationally-based methods and which provides a simple user interface is described. Several sets of far-field spectral density experimental data are decomposed into their large-scale turbulence component and the corresponding near-field wavenumber spectra are calculated. A wavepacket model is used to characterize the near-field wavenumber spectrum at the surface of the jet flow, and the wavepacket properties given by the near-field spectra at various frequencies and operating conditions are found using Gaussian fits. A large database is compiled from the wavepacket properties for a range of operating conditions, and the far-field jet noise is predicted using a mathematical model that combines the wavepacket model and existing models. Comparison of the wavepacket-model far-field supersonic jet noise predictions and experimental measurements are made, and the results demonstrate that the wavepacket-model results in accurate noise predictions.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 75
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Book Description
Three analytical models for near field noise calculation are formulated for subsonic and supersonic jet flows. Evaluation of these models in comparison with nearfield noise measurements from a full scale jet engine and scale model hot jets is presented. The use of compositions of different quadrupoles as prediction models is demonstrated. The effect of initial turbulence level on the near noise field was studied by the use of the analytical models. The results of the study indicate that an increase of the turbulence level in the jet exit plane causes an increase in sound pressure level for high frequencies. The effect of the turbulence level is negligible for low frequency sound. (Author).
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 104
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Author: William H. Mayes
Publisher:
ISBN:
Category :
Languages : en
Pages : 30
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Book Description
Near-field and far-field noise surveys were made of the supersonic The exhaust jet of the Langley 9- by 6-foot thermal structures tunnel. The jet had a thrust rating of approximately 475,000 pounds. The sound power radiated was found to be about 3.6 x 10(exp 6) watts, and on an acoustical-mechanical efficiency basis this value is in reasonable agreement with data for smaller supersonic jets and for rocket engines of other investigations. Octave-band analyses of the near-field noise show that the maximum sound pressure levels in the low-frequency bands are greatest downstream, whereas maximum sound pressure levels in the high-frequency bands were greatest near the jet exit. A comparison of near-field noise measurements is made with data previously obtained for rocket engines. Noise survey measurements of the original jet are compared with similar data obtained after the addition of a 97-foot-long exit diffuser section, and an example of the application of this facility to the problem of acoustic environmental testing of a large space capsule is cited.
Author: Reda R. Mankbadi
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 702
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Book Description
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781721276707
Category :
Languages : en
Pages : 26
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Book Description
An acoustic prediction capability for supersonic axisymmetric jets was developed on the basis of OVERFLOW Navier-Stokes CFD (Computational Fluid Dynamics) code of NASA Langley Research Center. Reynolds-averaged turbulent stresses in the flow field are modeled with the aid of Spalart-Allmaras one-equation turbulence model. Appropriate acoustic and outflow boundary conditions were implemented to compute time-dependent acoustic pressure in the nonlinear source-field. Based on the specification of acoustic pressure, its temporal and normal derivatives on the Kirchhoff surface, the near-field and the far-field sound pressure levels are computed via Kirchhoff surface integral, with the Kirchhoff surface chosen to enclose the nonlinear sound source region described by the CFD code. The methods are validated by a comparison of the predictions of sound pressure levels with the available data for an axisymmetric turbulent supersonic (Mach 2) perfectly expanded jet. Kandula, Max and Caimi, Raoul and Steinrock, T. (Technical Monitor) Kennedy Space Center NASA/TM-2001-210263, NAS 1.15:210263
Author: Max Kandula
Publisher: BiblioGov
ISBN: 9781289269005
Category :
Languages : en
Pages : 28
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Book Description
An acoustic prediction capability for supersonic axisymmetric jets was developed on the basis of OVERFLOW Navier-Stokes CFD (Computational Fluid Dynamics) code of NASA Langley Research Center. Reynolds-averaged turbulent stresses in the flow field are modeled with the aid of Spalart-Allmaras one-equation turbulence model. Appropriate acoustic and outflow boundary conditions were implemented to compute time-dependent acoustic pressure in the nonlinear source-field. Based on the specification of acoustic pressure, its temporal and normal derivatives on the Kirchhoff surface, the near-field and the far-field sound pressure levels are computed via Kirchhoff surface integral, with the Kirchhoff surface chosen to enclose the nonlinear sound source region described by the CFD code. The methods are validated by a comparison of the predictions of sound pressure levels with the available data for an axisymmetric turbulent supersonic (Mach 2) perfectly expanded jet.
