This content is not included in
your SAE MOBILUS subscription, or you are not logged in.
Predicting Turbulent Decorrelation in Acoustic Phased Array in a Turbulent Medium
Technical Paper
2014-36-0765
ISSN: 0148-7191, e-ISSN: 2688-3627
Annotation ability available
Sector:
Language:
English
Abstract
The use of a microphone array for acoustic measurements in wind tunnels is known to degrade the sound pressure levels and dynamic range of the acoustic image, due to the decorrelation between each pair of microphones, after the acoustic wave has crossed the turbulent boundary layer of the wind tunnel.
Based on a large number of studies in the areas of radiophysics, underwater acoustics and atmospheric science, this paper describes research on a physical model of wave propagation in a turbulent medium and its stochastic solution, obtaining as a solution the statistical momentum of the wave signal after it has propagated through the turbulent medium. The parabolic equation for acoustic wave propagation is considered and the Markov approximation is assumed for the stochastic solution of the wave. The signal coherence between each pair of microphones is the amount considered responsible for the decorrelation of the signals. Thus, the statistic to be considered for the stochastic solution of the equation is the coherence of the wave after it has crossed the turbulent boundary layer. In the model developed, this amount is represented by the second order coherence function.
Hot-wire measurements were carried out and the turbulence parameters were inserted into the model. Acoustic phased array measurements were performed and the results show agreement with the predictions, validating the use of the model for wind tunnel conditions and assumptions. Theoretical turbulence models for correlation were studied and the results used to validate the type of turbulent correlations for the wind tunnel.
Recommended Content
Technical Paper | Validation of SEA Wind Noise Model for a Design Change |
Technical Paper | The Chrysler 3/8-Scale Pilot Wind Tunnel |
Technical Paper | An Experimental Analysis and Estimation of Aerodynamic Noise Using a Production Vehicle |
Authors
Citation
Pires, L., Dougherty, R., and Gerges, S., "Predicting Turbulent Decorrelation in Acoustic Phased Array in a Turbulent Medium," SAE Technical Paper 2014-36-0765, 2014, https://doi.org/10.4271/2014-36-0765.Also In
References
- Mueller , T. J. Aeroacoustics measurements Springer Berlin 2002
- Dougherty , R. P. Turbulence Decorrelation of Aeroacoustic Phased Arrays: Lessons from Atmospheric Science and Astronomy AIAA Paper 03-3200, 9th AIAA/CEAS Aeroacoustics Conference and Exhibit Hilton Head, USA May 10 12 2003
- Schlinker , R.H. , Amiet , R.K. Airfoil Trailing Edge Measurements with a Directional Microphone AIAA Paper 1977 77-1269
- Dougherty , R.P. and Stoker R.W. Sidelobe Suppression for Phased Array Aeroacoustic Measurements AIAA Paper 98-2242 1998
- Wilson , D.K. Performance bounds for acoustic direction-of-arrival arrays operating in atmospheric turbulence J. Acoust. Soc. Am. 103 3 1998 1306 1319
- Tatarski , V.I Wave Propagation in a Turbulent Medium Silverman R.A. McGraw-Hill New York 1961
- Rytov , S.M. , Kravtsov , Y. A. , Tatarskii , V. L. Principles of Statistical Radiophysics, Part 4. Wave Propagation Through Random Media Springer-Verlag Berlim 1978
- Ostashev , V. E. Sound Propagation and Scattering in Media with Random Inhomogeneities of Sound Speed, Density and Medium Velocity Waves in Random Media 4 1994 403 428
- Wilson , D.K. Performance Bounds for Acoustic Direction-of-Arrival Arrays Operating in Atmospheric Turbulence J. Acoust. Soc. Am. 103 3 1998 1306 1319
- Ishimamuru , A. Wave Propagation and Scattering in Random Media Academic New York 1978
- Rytov , S.M. , Kravtsov , Y. A. , Tatarskii , V. L. Principles of Statistical Radiophysics, Part. 2: Correlation Theory of Random Processes Springer-Verlag Berlim 1978
- Ostashev , V. E. , Brähler , B. , Mellert , V. , Goedecke , G. H. Coherence Functions of Plane and Spherical Waves in a Turbulent Medium with the Von Karman Spectrum of Media Inhomogeneities J. of Acoustic Society of America 104 2 1998 725 737
- Corones , J. Bremmer Series that Correct Parabolic Approximations Journal of Mathematical Analysis and Applications 50 1975 361 372
- Gurvich , A. S. , Tatarskii , V. I. Coherence and intensity fluctuations of light in the turbulent atmosphere Radio Science 10 1 1975 3 14
- Dashen , Roger Path Integrals for Waves in Random Media Journal of Mathematic Physics 20 5 1979 894 920