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Quantification and adjustment of pixel-locking in particle image velocimetry

Authors
  • Hearst, R. J.1
  • Ganapathisubramani, B.1
  • 1 University of Southampton, Engineering and the Environment, Southampton, SO17 1BJ, UK , Southampton (United Kingdom)
Type
Published Article
Journal
Experiments in Fluids
Publisher
Springer-Verlag
Publication Date
Sep 24, 2015
Volume
56
Issue
10
Identifiers
DOI: 10.1007/s00348-015-2062-z
Source
Springer Nature
Keywords
License
Yellow

Abstract

A quantification metric is provided to determine the degree to which a particle image velocimetry data set is pixel-locked. The metric is calculated by integrating the histogram equalization transfer function and normalizing by the worst-case scenario to return the percentage pixel-locked. When this metric is calculated for each position in the vector field, it is shown that pixel-locking is non-uniform across the field. Hence, pixel-locking adjustments should be made on a vector-by-vector basis rather than uniformly across a field, although the latter is the common practice. A methodology is provided to compensate for the effects of pixel-locking on a vector-by-vector basis. This includes applying a Gaussian filter directly to the images, processing the images with window deformation, ensuring the vector fields are in pixel displacements, applying histogram equalization calculated at each vector coordinate, and mapping the adjusted vector fields to physical space.

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