Journal ArticleDOI
Stereoscopic Digital Particle Image Velocimetry for Application in Wind Tunnel Flows
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TLDR
In this article, a particle image velocimetry system based on a stereoscopic viewing arrangement is realized, which is capable of accurately recovering the out-of-plane velocity component of a vortex ring passing through a laser light sheet.Abstract:
A particle image velocimetry system capable of accurately recovering the out-of-plane velocity component has been realized based on a stereoscopic viewing arrangement. To allow a large viewing angle with long focal length objective lenses, the angular displacement or Scheimpflug imaging configuration is employed in which the image, object and lens planes intersect in a common line. The varying magnification factor associated with this imaging configuration is accounted for using an accurate and simple-to-use calibration procedure based on solving the projection equations for each of the two cameras. A pair of high-resolution cameras, both capable of recording image pairs in the microsecond range, are synchronized to a pulsed Nd-YAG laser. By placing the cameras on either side of the light sheet the favourable light scattering characteristics of micron-sized seeding particles in forward scatter provide images at significantly higher illumination than at normal or backscatter viewing angles. Ultimately designed for use in industrial wind tunnels, the camera system is capable of working with non-symmetric arrangements. It has been successfully tested in a laboratory environment by imaging the unsteady flow field of a vortex ring passing through a laser light sheet. Adaptive processing software capable of dynamically adjusting the sample location of the interrogation windows to the local displacement vector significantly improves data yield. The algorithm requires only the selection of the final window/overlap size. The hierarchical interrogation approach permits the processing of images whose displacement dynamic range exceeds the interrogation window size.read more
Citations
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Journal ArticleDOI
Tomographic particle image velocimetry
TL;DR: In this paper, a tomographic particle image velocimetry (tomographic-PIV) system based on the illumination, recording and reconstruction of tracer particles within a 3D measurement volume is described.
Theory of cross-correlation analysis of PIV images : Image analysis as measuring technique in flows
R. D. Keane,R. J. Adrian +1 more
TL;DR: In this article, cross-correlation methods of interrogation of successive single-exposure frames can be used to measure the separation of pairs of particle images between successive frames, which can be optimized in terms of spatial resolution, detection rate, accuracy and reliability.
Journal ArticleDOI
Tomographic PIV: principles and practice
TL;DR: A survey of the major developments in 3D velocity field measurements using the tomographic particle image velocimetry (PIV) technique is given in this article, where the fundamental aspects of the technique are discussed beginning from hardware considerations for volume illumination, imaging systems, their configurations and system calibration.
Journal ArticleDOI
Volume self-calibration for 3D particle image velocimetry
TL;DR: In this article, a volumetric self-calibration technique was developed based on the computation of the 3D position of matching particles by triangulation as in 3D-PTV.
Journal ArticleDOI
Stereo-PIV using self-calibration on particle images
TL;DR: In this paper, a stereo-PIV calibration procedure is developed based on fitting a camera pinhole model to the two cameras using single or multiple views of a 3D calibration plate, and a disparity vector map is computed on real particle images by cross-correlation of the images from cameras 1 and 2 to determine if the calibration plate coincides with the light sheet.
References
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Journal ArticleDOI
Particle-Imaging Techniques for Experimental Fluid Mechanics
TL;DR: A review of these methods can be found in articles by Lauterborn & Vogel (1984), Adrian (1986a), Hesselink (1988), and Dudderar et al..
Journal ArticleDOI
Digital Particle Image Velocimetry
Christian Willert,Morteza Gharib +1 more
TL;DR: In this article, the directional ambiguity associated with PIV and LSV is resolved by implementing local spatial cross-correlations between two sequential single-exposed particle images, and the recovered velocity data are used to compute the spatial and temporal vorticity distribution and the circulation of the vortex ring.
Theory of cross-correlation analysis of PIV images : Image analysis as measuring technique in flows
R. D. Keane,R. J. Adrian +1 more
TL;DR: In this article, cross-correlation methods of interrogation of successive single-exposure frames can be used to measure the separation of pairs of particle images between successive frames, which can be optimized in terms of spatial resolution, detection rate, accuracy and reliability.
Journal ArticleDOI
Theory of cross-correlation analysis of PIV images
TL;DR: In this paper, cross-correlation methods of interrogation of successive single-exposure frames can be used to measure the separation of pairs of particle images between successive frames, which can be optimized in terms of spatial resolution, detection rate, accuracy and reliability.