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Spontaneous acoustic emission from strong ionizing shocks

Published online by Cambridge University Press:  26 April 2006

M. Mond  and
I. M. Rutkevich
M. Mond
Affiliation:
Department of Mechanical Engineering, Ben-Gurion University of the Negev, PO Box 653, Beer Sheva 84105, Israel
I. M. Rutkevich
Affiliation:
Department of Mechanical Engineering, Ben-Gurion University of the Negev, PO Box 653, Beer Sheva 84105, Israel
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Abstract

Dyakov (1954) and Kontorovich (1957) formulated the conditions for corrugation instability of shock waves as well as for spontaneous emission of sound and entropy-vortex waves from them. For the first time since then, it is shown here that physical circumstances do exist under which shocks in gases spontaneously emit sound waves. Such circumstances are provided by strong ionizing shocks. In order to see that, the coefficient of reflection of an acoustic wave from a shock is derived as a function of the wave's frequency and the ionization degree. Spontaneous emission of sound occurs when the reflection coefficient becomes infinitely large. It is shown that the relevant frequency range for the occurrence of spontaneous emission is that for which the electrons are not in local thermodynamic equilibrium with the heavy particles. The special properties of acoustic perturbations behind the ionizing shock are considered for this frequency range and the sound velocity in a partially ionized gas is derived. In addition, the condition for spontaneous emission of sound is modified in order to take into account the difference between the electrons and heavy-particle perturbed temperatures. It is shown, by numerical calculations, that the criterion for spontaneous emission is satisfied behind ionizing shocks in argon. In particular, for an initial pressure of 5 Torr, the threshold for the occurrence of the spontaneous emission is found to be M1 = 15. This critical value of the shock Mach number, as well as other calculated physical features, agree very well with those obtained experimentally by Glass & Liu (1978) who observed the occurrence of instability behind shocks in argon.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 275 , 25 September 1994 , pp. 121 - 146
Copyright
© 1994 Cambridge University Press

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References

Anderson, J. D. 1989 Hypersonic and High Temperature Gas Dynamics. McGraw-Hill.
Biberman, L. M., Mnatsakanyan, A. KH. & Iakubov, I. T. 1970 Ionization relaxation behind strong shock waves in gases. Sov. Phys. Usp. 102 (3), 431–462.Google Scholar
Brillouin, J. 1953 Reflexion et refraction d’ondes acoustique par une onde de choc. Acustica 5 (3), 149–163.Google Scholar
Dyakov, S. P. 1954 On the stability of shock waves. Zh. Eksp. Teor. Fiz. 27 (9), 288–295.Google Scholar
Fowles, G. R. 1981 Stimulated and spontaneous emission of acoustic waves from shock fronts. Phys. Fluids 24, 220–227.Google Scholar
Glass, I.I. & Liu, W. S. 1978 Effects of hydrogen impurities on shock structure and stability in ionizing monatomic gases. Part 1. Argon. J. Fluid Mech. 84, 55–77.Google Scholar
Glass, I.I., Liu, W. S. & Tang, F. C. 1977 Effects of hydrogen impurities on shock structure and stability in ionizing monatomic gases: 2. Krypton. Can. J. Phys. 55, 1269–1279.Google Scholar
Griffiths, R. W., Sandeman, R. J. & Hornung, H. G. 1976 The stability of shock waves in ionizing and dissociating gases. J. Phys. D: Appl. Phys. 9, 1681–1691.Google Scholar
Kaniel, A., Igra, O., Ben-Dor, G. & Mond, M. 1986 Ionization behind strong shocks in argon. Phys. Fluids 29, 3618–3625.Google Scholar
Kontorovich, V. M. 1957 On the stability of shock waves. Zh. Ekspr. Teor. Fiz. 33, 1525–1526.Google Scholar
Kontorovich, V. M. 1959 Reflection and refraction of sound by shock waves. Akust. Zh. 5 (3), 314–323.Google Scholar
Kuznetsov, N. M. 1989 Stability of shock waves. Sov. Phys. Usp. 32 (11), 993–1012.Google Scholar
Landau, L. D. & Lifshitz, E. M. 1987 Fluid Mechanics, 2nd Edn. Pergamon.
Liberman, M. A. & Velikovich, A. L. 1986 Physics of Shock Waves in Gases and Plasmas. Springer.
Mitchner, M. & Kruger, C. H. 1973 Partially Ionized Gases. John Wiley & Sons.
Rutkevich, I. M. & Mond, M. 1992 Amplification of fast magnetosonic waves and the cutoff spectrum. J. Plasma Phys. 48, 345–357.Google Scholar