Sage Journals: Discover world-class research

Abstract

The application of microphone arrays for aeroacoustic measurements in wind tunnels with an open test section requires to consider the sound refraction at the shear layer. Several methods are available for this that are either applicable to special scenarios such as planar or cylindrical thin shear layers or that require considerable computational effort. The paper concerns a new method for general application—ray casting—that is based on a ray tracing method. Ray tracing is briefly revisited and it is shown that the computational effort becomes quite high especially for large mapping grids. The ray casting approach with its interpolation technique is introduced. A time reversal technique is the key to make this approach very efficient and fast. Finally, the approach is demonstrated using two example results from simulation and from a practical measurement.

Keywords

Ray tracing sound refraction microphone array

Get full access to this article

View all access options for this article.

References

Amiet

. Refraction of sound by a shear layer. J Sound Vib 1978; 58: 467–482.

Morfey

Joseph

. Shear layer refraction corrections for off-axis sources in a jet flow. J Sound Vib 2001; 239: 819–848.

Casalino

. Finite element solutions of a wave equation for sound propagation in sheared flows. AIAA J 2012; 50: 37–45.

Padois

Prax

Valeau

. Numerical validation of shear flow corrections for beamforming acoustic source localisation in open wind-tunnels. Appl Acoust 2013; 74: 591–601.

Jiao J, Delfs J and Dierke J. Towards CAA based acoustic wind tunnel corrections for realistic shear layers. In: Twenty-first AIAA/CEAS aeroacoustics conference, no. AIAA 2015-3278, Dallas, Texas, 22–26 June 2015. New York: American Institute of Aeronautics and Astronautics.

Redonnet S and Bulte J. Numerical investigation of the refraction effects by jet flows in anechoic wind tunnels, with application to NASA/LaRC quiet flow facility. In: Twenty-first AIAA/CEAS aeroacoustics conference, no. AIAA 2015-3268, Dallas, Texas, 22–26 June 2015. New York: American Institute of Aeronautics and Astronautics.

Uginčius

. Ray acoustics and Fermat’s principle in a moving inhomogeneous medium. J Acoust Soc Am 1972; 51: 1759–1763.

Candel S. Application of geometrical techniques to aeroacoustic problems. In: Third AIAA aeroacoustics conference, no. AIAA 76-546, Palo Alto, California, 20–23 July 1976. New York: American Institute of Aeronautics and Astronautics.

Candel

. Numerical solution of conservation equations arising in linear wave theory: application to aeroacoustics. J Fluid Mech 1977; 83: 465–493.

10.

Pierce

. Acoustics: an introduction to its principles and applications, New York, NY: American Institute of Physics, 1989.

11.

Dougherty

Beamforming in acoustic testing. In: Mueller

(ed). Aeroacoustic measurements, Berlin Heidelberg, Germany: Springer, 2002, pp. 62–97.

12.

Geyer

Sarradj

Giesler

. Application of a beamforming technique to the measurement of airfoil leading edge noise. Adv Acoust Vib 2012; 2012: 1–16.

13.

Albertson

Dai

Jensen

. Diffusion of submerged jets. Trans Am Soc Civ Eng 1950; 115: 639–664.

14.

Sarradj E. A Python framework for microphone array data processing. Appl Acoust 2017; 88; 50–58.

15.

Brown

Byrne

Hindmarsh

. VODE: a variable-coefficient ODE solver. SIAM J Sci Stat Comput 1989; 10: 1038–1051.

16.

Sarradj

. Three-dimensional acoustic source mapping with different beamforming steering vector formulations. Adv Acoust Vib 2012; 2012: 1–12.

17.

Geyer

Sarradj

Fritzsche

. Measurement of the noise generation at the trailing edge of porous airfoils. Exp Fluids 2010; 48: 291–308.

18.

Sarradj

Fritzsche

Geyer

. Acoustic and aerodynamic design and characterization of a small-scale aeroacoustic wind tunnel. Appl Acoust 2009; 70: 1073–1080.

A fast ray casting method for sound refraction at shear layers

Abstract

Keywords

Get full access to this article

References