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New Explanation of Noise Production by Supersonic Jets with Gas Dredging

  • H. Oertel Sen
  • F. Seiler
  • J. Srulijes
Part of the Notes on Numerical Fluid Mechanics and Multidisciplinary Design book series (NNFM, volume 112)

Summary

Supersonic jets emit Mach waves producing noise in their environment. Various experimental techniques have been used in the past for investigating the behaviour of structures present in the supersonic jet boundary layer. These structures are accompanied by long, almost straight and nearly parallel Mach waves. These Mach waves appear both outside and inside the jet. It was experimentally found that these Mach waves move at three preferred speeds: w, w’ and w”. They depend simply and exclusively on the jet Mach number Mi and the speed of sound ratio between inside (ai) and outside (aa) of the jet. Quite simple empiric formulae for w, w’ and w” have been established by Oertel sen. but no satisfying explanation could be found at that time. Recently, however Oertel sen. proposed a new idea based on the growth of long living pairs of vortices formed inside of the jet boundary layer. Vortices move with the velocities w’ and w” respectively, whereas the centre of the pair moves with w. The w’- and w”-vortices move supersonically with respect to aa, therefore produce the so-called w’ -Mach waves outside of the jet. The w” - vortices move with ui – w” > ai , therefore produce the so-called w”-Mach waves inside of the jet. This theory suggests a new method of jet noise reduction.

Keywords

Mach Number Shear Layer Shock Tube Mach Wave Relative Mach Number 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2010

Authors and Affiliations

  • H. Oertel Sen
    • 1
  • F. Seiler
    • 2
  • J. Srulijes
    • 2
  1. 1.Retired from the French-German Research Institute of Saint-Louis (ISL) 
  2. 2.French-German Research Institute of Saint-Louis (ISL)Saint-LouisFrance

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