15 May 1981 Optical Correlation Techniques In Fluid Dynamics
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Proceedings Volume 0236, 1980 European Conf on Optical Systems and Applications; (1981); doi: 10.1117/12.959014
Event: 1980 European Conference on Optical Systems and Applications, 1980, Utrecht, Netherlands
Abstract
Three flow measurement techniques make use of fast digital correlators. (1) Most widely spread is photon correlation velocimetry using crossed laser beams and detecting Doppler shifted light scattered by small particles in the flow. Depending on the processing of the photon correlogram, this technique yields mean velocity, turbulence level, or even the detailed probability distribution of one velocity component. An improved data processing scheme is demonstrated on laminar vortex flow in a curved channel. (2) Rate correlation based upon threshold crossings of a high pass filtered laser Doppler signal can he used to obtain velocity correlation functions. The most powerful setup developed in our laboratory uses a phase locked loop type tracker and a multibit correlator to analyse time-dependent Taylor vortex flow. With two optical systems and trackers, crosscorrelation functions reveal phase relations between different vortices. (3) Making use of refractive index fluctuations (e. g. in two phase flows) instead of scattering particles, interferometry with bidirectional fringe counting and digital correlation and probability analysis constitute a new quantitative technique related to classical Schlieren methods. Measurements on a mixing flow of heated and cold air contribute new ideas to the theory of turbulent random phase screens.
© (1981) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
K. Schatzel, E. O. Schulz-DuBois, R. Vehrenkamp, "Optical Correlation Techniques In Fluid Dynamics", Proc. SPIE 0236, 1980 European Conf on Optical Systems and Applications, (15 May 1981); doi: 10.1117/12.959014; https://doi.org/10.1117/12.959014
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KEYWORDS
Doppler effect

Optical correlators

Particles

Phase measurement

Analog electronics

Light scattering

Correlation function

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