24 May 2018 Fluid flow measurements using optical flow velocity field estimation and LED-based light sheet illumination
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The aim of this work is to present a technique for non-intrusive velocity vector measurements of micron-sized tracer particles following a fluid flow. The technique is based on Particle Image Velocimetry (PIV). In contrast to conventional PIV, which analyzes light scattering for incident high-energy laser pulses, the technique uses a light sheet produced by a prototype LED-based illuminator. A sequence of exposures from the flow taken by a high-speed camera is analyzed by means of a multi-scale optical flow-based algorithm developed by the authors. The LED illuminator offers the possibility to deliver high-power light pulses at microsecond levels and high-repetition rates. An integrated optics produce a lightsheet with adjustable thickness and width, enabling the user to measure velocity components either in a plane or in a volume. Compared to pulse lasers used in PIV systems, the illuminator has the advantages of low cost, safe operation, and much simpler construction. For the purposes of experimental verification, velocity vector measurements in a crosssection of a rotary water flow seeded with micron sized tracer particles have been performed. The velocity vectors have been computed using a multi-scale estimation algorithm based on optical flow and four-level pyramidal decomposition of PIV images. In order to validate our optical flow-based approach, the experimental results have been finally analyzed by means of a commercial PIV software that uses image cross-correlation for velocity field estimation.
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Grzegorz Głomb, Grzegorz Głomb, Grzegorz Świrniak, Grzegorz Świrniak, "Fluid flow measurements using optical flow velocity field estimation and LED-based light sheet illumination", Proc. SPIE 10679, Optics, Photonics, and Digital Technologies for Imaging Applications V, 106791L (24 May 2018); doi: 10.1117/12.2306644; https://doi.org/10.1117/12.2306644


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