Space-time correlation measurements in subsonic and supersonic jets using optical deflectometry

Benoît P. Petitjean, K. Viswanathan, Dennis K. McLaughlin, Philip J. Morris

Research output: Chapter in Book/Report/Conference proceedingConference contribution

13 Scopus citations


The flow fields of round and beveled nozzle jets have been investigated with the goal of gaining some insights into the flow characteristics responsible for the observed changes in the radiated noise for the two geometries. Two different optical techniques, qualitative schlieren pictures and quantitative optical deflectometry measurements, have been employed to complement the farfield acoustics measurements. Three different cases with nominal Mach numbers of 0.6, 0.9 and 1.5 are considered. The calculated plume deflections from the schlieren pictures are in agreement with those from previous force measurements on the same jet flows; these images also helped in the proper positioning of the optical deflectometry sensing volumes. An examination of the coherence spectra in the shear layer for the subsonic jets reveals notable differences between the circular and beveled jets. In contrast to the round jet which has a clearly defined peak at a Strouhal number of ~0.4, the spectra acquired on both long and short lip sides of the beveled nozzle show a significant spectral broadening for Strouhal numbers in the range 0.0-0.5, with no clearly marked peak; the jets from the beveled nozzles contain a much broader range of turbulence scales than the circular jets in the shear layer, four diameters downstream. The measured convective velocity ratios for both nozzles lie in the range of 0.71 to 0.74 for subsonic jets, in line with past measurements. The peak correlation levels are lower in beveled jets than in circular jets. The trends for the supersonic jet are quite different. The cross-correlation functions on the shorter lip side of the beveled nozzle are somewhat weaker with lower peak correlation levels, indicating a faster decay of turbulence. This study, using optical techniques, represents one component of a comprehensive experimental and numerical program aimed at gaining a better understanding of the sources of jet noise, particularly in jets from beveled nozzles.

Original languageEnglish (US)
Title of host publication13th AIAA/CEAS Aeroacoustics Conference (28th AIAA Aeroacoustics Conference)
PublisherAmerican Institute of Aeronautics and Astronautics Inc.
ISBN (Print)9781624100031
StatePublished - 2007
Event13th AIAA/CEAS Aeroacoustics Conference (28th AIAA Aeroacoustics Conference) - Rome, Italy
Duration: May 21 2007May 23 2007

Publication series

Name13th AIAA/CEAS Aeroacoustics Conference (28th AIAA Aeroacoustics Conference)


Other13th AIAA/CEAS Aeroacoustics Conference (28th AIAA Aeroacoustics Conference)

All Science Journal Classification (ASJC) codes

  • Aerospace Engineering
  • Mechanical Engineering


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