Abstract
Even though supersonic flows have been studied for a long time, many questions remain unanswered about their behavior. The understanding of jet noise goes in parallel with the understanding of jet turbulence. It has been speculated that different kinds of vortex interactions in the near field, can produce sound. Also, that the interaction between the flow and the shock structure produces noise. It is now known that noise, in supersonic and subsonic jets, is made up of two basic components; one from the large turbulence structures and instability waves, and the other from the fine-scale turbulence. Measurements inside a supersonic jet are difficult. Hot wires are easily broken and homogeneous seeding for Laser Doppler and Particle Image Velocimetries is complicated. We have developed a non-intrusive technique that uses the heterodyne detection of Rayleigh scattering. The laser light scattered elastically by the molecules of the flow at a particular angle, has information about density fluctuations of a particular size. It can be shown that the signal that comes out of a quadratic photo detector is proportional to the spatial Fourier transform as a function of time, of the density fluctuations for a wave vector given by the scattering angle. The spectral analysis of the data has allowed us to identify fluctuations of different origins; entropic and acoustic. We have taken data at many points inside and outside the flow. The technique is sensitive to the wave vector so we can study fluctuations that propagate in different directions. Fluctuations in the direction of the flow are shifted in frequency with respect to fluctuations perpendicular to the flow at the same location. The frequency shift allows us to measure the local speed of the flow. Outside the flow, only acoustic fluctuations are detected. We have been able to determine the far field acoustic radiation pattern for a given wave vector. Inside the jet, the analysis is much more complicated because the acoustic and the entropic peaks overlap when we use simple Fourier transforms. However, with the use of parametric periodgrams we have been able to identify each type of fluctuation. Moreover, we found a third peak at a much lower frequency that appears and disappears as we move along the centerline of the jet. This peak appears also in other positions outside the centerline. We have used Rayleigh scattering and Schlieren to visualize the shock structure. We can then associate each spectrum with a position in the jet relative to the shock structure. The slow peak appears always at a shock, probably due to the interaction between the flow and the shock structure. We are now working on the visualization of the flow, and hope that the combination of all the techniques will give us further insight into the global behavior of the flow, especially in the interfaces between the flow and the shocks and between the mixing layer and the stationary fluid.
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References
Aguilar C (2003) Detection of acoustic waves in a supersonic jet using Rayleigh scattering. BS thesis, Department of Physics, School of Science, UNAM, Mexico City, Mexico
Alvarado Reyes JM (2004) Spectral analysis of signals from Rayleigh scattering experiment. M.E, Thesis, School of Engineering, UNAM, Mexico City, Mexico
Alvarado Reyes JM (2010) Técnicas modernas para el tratamiento de señales turbulentas, PhD thesis, Universidad Nacional Autónoma de México
Azpeitia C (2004) Use of Rayleigh scattering to localize acoustic sources in a supersonic jet. BS thesis, Department of Physics, School of Science, UNAM, Mexico City, Mexico
Bodonyy DJ, Lele SK (2006) Low frequency sound sources in high-speed turbulent jets. Annual Research Briefs, Center for Turbulence Research, Stanford University, Palo Alto. Ca, USA
Carreño Rodríguez AS (2010) Reconstruction of gaussian beams to increase the spatial resolution in a Rayleigh scattering experiment. BS thesis, Department of Physics, School of Science, UNAM, Mexico City, Mexico
Chapman CJ (2000) High speed flow. Cambridge University Press, Cambridge
Echeverría Arjonilla C (2013) PIV measurements in a supersonic flow. BS Thesis, Department of Physics, School of Science, UNAM, Mexico City, Mexico
Goldstein ME (1976) Aeroacoustics, 1st edn. McGraw-Hill, USA
Goldstein RJ (1983) Fluid Mechanics Measurements, 1st edn. Edit, Hemisphere, USA
Jackson JD (1962) Classical electrodynamics. John Wiley & Sons Ltd, New York
Monin AS, Yaglom AM (1987) Statistical fluid mechanics. MIT Press, Cambridge
Nichols JW, Ham FE, Lele SK, Monin P, Ham FE, Lele SK, Moin P (2011) Prediction of supersonic jet noise from complex nozzles. Annual Research Briefs, Center for Turbulence Research, Stanford University, Palo Alto. Ca, USA
Panda J, Seasholtz R (1998) Density measurement in underexpanded supersonic jets using Rayleigh scattering. 36th AIAA Aerospace Sciences Meeting and Exhibit, 1998, 10.2514/6.1998-281
Porta D (2013) Interfaces in a supersonic jet using shadowgraphs. BS Thesis, Department of Physics, School of Science, UNAM, Mexico City, Mexico
Salazar Romero MY (2011) Advanzed optical techniques applied to fluid dynamics. BS Thesis, Department of Physics, School of Science, UNAM, Mexico City, Mexico
Settles GS (2001) Schlieren and shadowgraph techniques. Visualizing Phenomena in Transparent Media, Edit, Springer, USA
Stern C, Grésillon D (1983) Fluctuations de Densité dans la Turbulence d’un Jet. Observation par Diffusion Rayleigh et Détection Heterodyne. J Phys 44:1325–1335
Tam C (2012) Computational aeroacoustics: A wave number approach. Cambridge University Press, Cambridge
Tam C (1998) Jet Noise: Since 1952. In: Theoretical and computational fluid dynamics. Springer, New York
Tam C (1992) Broadband shock associated noise from supersonic jets measured by a ground observer. 30th Aerospace Sciences Meeting and Exhibit, 1992, 10.2514/6.1992-502
Veltin J (2008) On the characterization of noise sources in supersonic shock containing jets. PhD Thesis, Pennsylvania State University, Google Books
Yariv A (1976) Introduction to optical electronics. Holt, Rinehart and Winston, New York
Acknowledgments
We acknowledge support from UNAM through DGAPA projects IN107599, IN104102, IN116206 and IN117712. Also the participation of several undergraduate students: Cesar Aguilar, Carlos Azpeitia, Alejandro Carreño, Yadira Salazar, Carlos Echeverría, and David Porta.
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Forgach, C.S., Reyes, J.M.A. (2014). Shock Structure and Acoustic Waves in a Supersonic Jet. In: Sigalotti, L., Klapp, J., Sira, E. (eds) Computational and Experimental Fluid Mechanics with Applications to Physics, Engineering and the Environment. Environmental Science and Engineering(). Springer, Cham. https://doi.org/10.1007/978-3-319-00191-3_9
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DOI: https://doi.org/10.1007/978-3-319-00191-3_9
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