Particle image velocimetry : data reduction using optical correlation
Particle image velocimetry : data reduction using optical correlation
Fundamental research into a new measurement technique in fluid dynamics called particle image velocimetry (PIV) is presented. This non-intrusive technique provides a means of mapping instantaneous flow fields in unsteady fluid flows. In its simplest form, PIV uses double exposure photography to record the position of seeding particles found within a thin light sheet illuminating a section from the flow of interest. Analysis of the resulting transparency involves multiple point measurement of the displacement associated with random patterns of particle images. If the time interval between the exposures and the magnification of the recording optics are known then these displacement measurements can be related to the fluid velocity and a two-dimensional flow map can be constructed. As a simple and cost effective solution to the problem of PIV transparency analysis, optical methods which perform rapid calculation of two-dimensional spatial autocorrelation, are discussed. Both incoherent and coherent techniques are considered and the performance of each examined with reference to PIV data reduction. A fully automated transparency analysis system, based on a new design of optical autocorrelator, is described and applied to the study of several flows of varying complexity. In a theoretical treatment, the choice of experimental parameters, such as the size of seeding particles, is related to the type of velocity field which can be examined in this way. Having developed a basis for PIV system design, the practical problems associated with photographing the fluid flow are investigated and a versatile and inexpensive light source based on a linear Xenon flashlamp is described for this purpose. Finally, a combination of alternative methods to record the light scattered by the seeding particles with optical correlation analysis are examined. Methods to overcome the 180o ambiguity inherent in conventional photographic recordings and the extension of PIV for the whole field, three-dimensional measurement of fluid velocity fields are discussed.
University of Southampton
1990
Coupland, Jeremy Michael
(1990)
Particle image velocimetry : data reduction using optical correlation.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Fundamental research into a new measurement technique in fluid dynamics called particle image velocimetry (PIV) is presented. This non-intrusive technique provides a means of mapping instantaneous flow fields in unsteady fluid flows. In its simplest form, PIV uses double exposure photography to record the position of seeding particles found within a thin light sheet illuminating a section from the flow of interest. Analysis of the resulting transparency involves multiple point measurement of the displacement associated with random patterns of particle images. If the time interval between the exposures and the magnification of the recording optics are known then these displacement measurements can be related to the fluid velocity and a two-dimensional flow map can be constructed. As a simple and cost effective solution to the problem of PIV transparency analysis, optical methods which perform rapid calculation of two-dimensional spatial autocorrelation, are discussed. Both incoherent and coherent techniques are considered and the performance of each examined with reference to PIV data reduction. A fully automated transparency analysis system, based on a new design of optical autocorrelator, is described and applied to the study of several flows of varying complexity. In a theoretical treatment, the choice of experimental parameters, such as the size of seeding particles, is related to the type of velocity field which can be examined in this way. Having developed a basis for PIV system design, the practical problems associated with photographing the fluid flow are investigated and a versatile and inexpensive light source based on a linear Xenon flashlamp is described for this purpose. Finally, a combination of alternative methods to record the light scattered by the seeding particles with optical correlation analysis are examined. Methods to overcome the 180o ambiguity inherent in conventional photographic recordings and the extension of PIV for the whole field, three-dimensional measurement of fluid velocity fields are discussed.
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Published date: 1990
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Local EPrints ID: 461781
URI: http://eprints.soton.ac.uk/id/eprint/461781
PURE UUID: 0ccca616-ea22-40d7-bee4-09de3968c441
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Date deposited: 04 Jul 2022 18:54
Last modified: 04 Jul 2022 18:54
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Author:
Jeremy Michael Coupland
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