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1 December 1991 Numerical and optical evaluation of particle image velocimetry images
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Abstract
Application of particle image velocimetry (PIV) techniques for measurement of fluid velocities typically requires two steps. The first of these, is the photography step, in which two exposures of a particle field, displaced between the exposures, are taken. The second step of the application is the evaluation of the double exposure particle pattern and production of appropriate particle velocities. Each of these steps involves optimization which is usually specific to the experiment being conducted and there is significant interaction between photographic parameters and evaluation characteristics. This paper will focus on the latter step, that of evaluation of the double exposure photograph.

Among the various evaluation techniques suggested for analysis of PIV images is the evaluation of the scattered interference pattern (Young's fringes) by numerical Fourier transform. An alternative to the numerical calculation of the Fourier transform of the Young's fringes has been suggested, using a modified liquid crystal television as an optical correlator to allow the transform to be performed optically, thus speeding up the interrogation process.

Both transform techniques are affected by the quality of the input function, specifically the Young's fringes. This paper will compare the performance of optical and numerical fourier transform analysis of Young's fringes using speckle images.

The repeatability and an estimate of the accuracy of the particle displacement will be shown for each method.
© (1991) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Patrick V. Farrell "Numerical and optical evaluation of particle image velocimetry images", Proc. SPIE 1554, Second International Conference on Photomechanics and Speckle Metrology, (1 December 1991); https://doi.org/10.1117/12.57447
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