3 edition of Propagation of high frequency jet noise using geometric acoustics found in the catalog.
Propagation of high frequency jet noise using geometric acoustics
by National Aeronautics and Space Administration, National Technical Information Service, distributor in [Washington, DC], [Springfield, Va
Written in English
|Statement||A. Khavaran and E.A. Krejsa.|
|Series||NASA technical memorandum -- 106013.|
|Contributions||Krejsa, E. A., United States. National Aeronautics and Space Administration.|
|The Physical Object|
Static engine run-up noise measurements have been made on the F Raptor at low and high power settings. At afterburner, the propagation measurements reveal significant evidence of nonlinearity in that there is much greater high-frequency energy than is predicted by linear theory. The measurements have been compared against the results of aFile Size: KB. aerodynamically generated noise provided the control surface surrounds the entire source region. However, for jet noise prediction, shear mean °ow ex-ists outside the control surface that causes refraction. The mean °ow refrac-tion corrections had been done in the past using simple geometric acoustics File Size: 1MB.
Noise measured in the vicinity of an FA Raptor has been compared to similarity spectra found previously to represent mixing noise from large-scale and fine-scale turbulent structures in laboratory-scale jet plumes. Comparisons have been made for three engine conditions using ground-based sideline microphones, which covered a large angular aperture.. Even though the nozzle geometry is Cited by: The geometrical acoustics capabilities of the COMSOL ® software can be used to evaluate high-frequency systems where the acoustic wavelength is smaller than the characteristic geometric features. There are two interfaces for computing geometric acoustics available with the Acoustics Module: Ray Acoustics and Acoustic Diffusion Equation.
Wave6 uses finite element analysis (FEA), statistical energy analysis (SEA), and boundary element method (BEM) models to simulate the transmissions of broadband, or low- and high-frequency, noise. Using CD-adapco’s “power session” licensing model, users can access these methods and connect them as needed. The long term goals of this project are to research the physics of high frequency ( kHz) acoustic propagation and ambient noise in the ocean. This work is relevant to many types of Navy sonars such as active ASW and MCM systems and underwater acoustic modems for communications. Improved understanding is leading to better ways to adapt to.
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Spherical directivity of noise radiated from a convecting quadrupole source embedded in an arbitrary spreading jet is obtained by ray-tracing methods of geometrical acoustics. The six propagation equations are solved in their general form in a rectangular coordinate system.
silence as well as the caustics of geometrical acoustics. A high frequency Green function for a convecting multipole source in a spreading jet was developed by P.
Durbin  and was applied to predict the directiv-ity of noise for a source convecting along the center-axis of an axisymmetric jet. The symmetric nature of this. Get this from a library.
Propagation of high frequency jet noise using geometric acoustics. [A Khavaran; E A Krejsa; United States. National Aeronautics and Space Administration.]. AIREX: Propagation of high frequency jet noise using geometric acoustics Spherical directivity of noise radiated from a convecting quadrupole source embedded in an arbitrary spreading jet is obtained by ray-tracing methods of geometrical acoustics.
The six propagation equations are solved in their general form in a rectangular coordinate system. High frequency geometrical acoustics based on ray-tracing methods is used to compute the spherical directivity of noise radiated from a convecting quadrupole source.
The source is placed at an arbitrary position within a spreading jet. The propagation equations are solved in their general form in a rectangular coordinate : Abbas Khavaran. Spherical directivity of noise radiated from a convecting quadrupole source embedded in an arbitrary spreading jet is obtained by ray-tracing methods of geometrical acoustics.
The six propagation equations are solved in their general form in a rectangular coordinate : E. Krejsa and A. Khavaran. The relevant acoustic-mean flow interactions are modeled by an approximation to the WKB type solution.
The original monopole solution is generalized to yield high-frequency solutions for the dipole and quadrupole sources used to model jet mixing by: 1. the source along the jet center line – and use a three-step calibration procedure for angle, distance and sound amplitude.
This procedure takes advantage of the high frequency geometric acoustics arguments, i.e., conservation of acoustic energy along a ray tube, and converts the noise measured outside the free jet to the levels that would be. acoustic waves propagating in the system. Pipe supports couple the system to various structures which may radiate acoustic noise more efficiently than the pipe system.
It is therefore important to consider all elements of the pipe system when treating noise and vibration. Noise File Size: KB. Mathematical formulation for the propagation of sound through a turbulent jet. Journal of Engineering Mathematics, Vol. 10, No. Recommended.
Propagation of high frequency jet noise using geometric acoustics. Acoustic wave propagation in an axisymmetric swirling by: 1 Prediction of jet mixing noise with Lighthill’s Acoustic Analogy 2 and geometrical acoustics AQ1 3 Carlos R.
Ilarioa) 4 EMBRAER S.A., Avenue Brigadeiro Faria Lima, S~ao Jos e dos Campos - SP, Brazil 5 Mahdi Azarpeyvand 6 Department of Mechanical Engineering, University of Bristol, Bristol, United Kingdom 7 Victor Rosa and Rod H.
Self 8 Institute of Sound and Vibration File Size: 2MB. Application of Geometrical Acoustics to Propagation of High Frequency Jet Noise Broadband scattering from shear flows and the non-doppler remote sensing of velocity profiles Journal of Sound and Vibration, Vol.No.
3Cited by: ies on the nonlinear propagation on noise from military jets have shown that the evolution of these shocks has a sig-nificant impact on the high-frequency portion of the spec-trum.
Nonlinear effects in jet noise have also been observed in supersonic laboratory30,31 scale jets. As an example28 of acoustic shocks in jet noise propaga. Request PDF | On the Far-Field Propagation of High-Speed Jet Noise | This paper deals with the effects of atmospheric absorption on the propagation of high-speed jet noise.
Keywords: nonlinear, propagation, jet, noise, supersonic, Burgers equation PACS: Nm, Cb, Wy INTRODUCTION In the analysis of high-amplitude jet noise for nonlinear acoustic propagation, limitations in measurement bandwidth and propagation range can create difficulties in.
An Introduction to Acoustics S.W. Rienstra & A. Hirschberg Eindhoven University of Technology 28 Nov This is an extended and revised edition of IWDE Comments and corrections are gratefully accepted.
This ﬁle may be used and printed, but for personal or educational purposes only. c S.W. Rienstra & A. Hirschberg Computational Acoustics of Noise Propagation in Fluids - Finite and Boundary Element Methods. Editors this comprises numerical issues, e.g. convergence, multi-frequency solutions and highly efficient methods; and secondly, solutions techniques for the particular difficulties that arise with external problems, e.g.
discussion of absorbing. ()]. Here, noise waveforms from a high-performance military jet aircraft are characterized with this gain factor and compared to propagation losses from geometric spreading and atmospheric absorption. Far-ﬁeld results show that the high-frequency nonlinear gains at.
NOISE CONTROL Outdoor Sound Propagation J. Lamancusa Penn State 7/20/ Review of Hemispherical Sound Propagation You should recall from Section 5, for a point source in a loss-less medium with no reflections, that the sound intensity is related to power and range by: 2 2 4 ()File Size: KB.
While large amounts of low frequency noise are pro-duced by wind turbines, it may be that, technically speaking, Proceedings of ACOUSTICS NovemberGold Coast, Australia Acoustics 1. Low frequency sound has been defined as that lying below the sound energy lies in the low frequency range with the high-est sound levels.
The prediction of jet noise has been the object of continuous interest and study since the introduction of the jet engine tbr commercial use.
The earliest theoretical formulation tbr aerodynamic noise was the work of Lighthill 2'3. Lighthill's equation was the first example of an "acoustic analogy."File Size: 1MB.This Interactive Sound Propagation Level Calculator is an approximate calculation tool and should not replace your own calculations and real life measurements.
Assumptions No transmission of sound around the barrier - therefore, the combined transmission of sound around the sides of the barrier must be at least 10dB below the level of sound.Prior computational methods for simulating the propagation of sound through an environment can be classiﬁed into three major approaches: 1) numerical solutions to the wave equation (e.g., ﬁ-nite and boundary element methods), 2) high frequency approximations based on geometric prop-File Size: 1MB.