Abstract. The objective of this work was the application of interferometry as a tool for non-intrusive measurement of frequency spectra in turbulent flows. Two laser vibrometer systems together with a signal analyser were used to obtain the frequency spectra of density fluctuations across a fully developed turbulent free jet. Since laser vibrometry is based on interferometric techniques the derived signals are path integrals along the measurement beam. To derive local information on the frequency spectra of density fluctuations long-time averaged measurements from each of the two systems were treated using correlation functions and cross spectra. Results were compared to spectral data from a pitot-mounted pressure sensor.

Keywords: interferometry, turbulence, laser vibrometer, coherence

Print publication: Issue 10 (October 2006)
Received 8 May 2006, in final form 16 July 2006
Published 20 September 2006