Experiments in Fluids

, Volume 13, Issue 2–3, pp 105–116 | Cite as

Effect of resolution on the speed and accuracy of particle image velocimetry interrogation

  • A. K. Prasad
  • R. J. Adrian
  • C. C. Landreth
  • P. W. Offutt
Originals

Abstract

Particle image velocimetry incorporates a process by which an image of a flow field, bearing double images of seeding particles, is analyzed in small regions called “interrogation spots.” Each spot is imaged onto a photodetector array whose digitized output is evaluated computationally using the auto-correlation technique. This paper examines the effects of resolving the spot using arrays of various resolutions, motivated primarily by a gain in speed. For this purpose, two specially created test photographs representing (i) uniform flow and (ii) solid body rotation, were interrogated using array sizes ranging from 32 × 32 to 256 × 256. Each reduction in resolution by a factor of two gains a factor of four in interrogation speed, but this benefit is counteracted by a loss in accuracy. The particle image diameter strongly influences accuracy through two distinct error mechanisms. When the particle image is small compared to the pixel size, mean bias error becomes significant due to finite numerical resolution of the correlation function. Conversely, when the particle image is large, random error due to irregularities in the electronic images predominates. The optimum image size, therefore, lies not at either extreme but at an intermediate value such that the particle image is small in an absolute sense, and yet large relative to the pixel size.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Adrian, R. J. 1988: Statistical properties of particle image velocimetry measurements in turbulent flow. Laser Anemometry in Fluid Mechanics, Vol. III, Lisbon: Ladoan — Instituto Superior Técnico, 115–129Google Scholar
  2. Adrian, R. J. 1991: Particle-imaging techniques for experimental fluid mechanics. Ann. Rev. Fluid Mech 23, 261–304Google Scholar
  3. Bjorkquist, D. J. 1990: Particle image velocimetry analysis system. Proc. Fifth Intl. Symp. on Applications of Laser Anemometry to Fluid Mechanics, Lisbon, Portugal, 12.1Google Scholar
  4. Keane, R. D. 1991: Private communicationGoogle Scholar
  5. Keane, R. D.; Adrian, R. J. 1990: Optimization of particle image velocimeters. Part I: Double pulsed systems. Meas. Sci. Technol. 1, 1202–1215CrossRefGoogle Scholar
  6. Landreth, C. C.; Adrian, R. J. 1988: Measurement and refinement of velocity data using high image density analysis in particle image velocimetry. Applications of Laser Anemometry to Fluid Mechanics (Eds.: Adrian, R. J., Asanuma, T., Durão, D. F. G., Durst, F., Whitelaw, J. H.). Berlin Heidelberg New York: Springer, pp 484–497Google Scholar
  7. Liu, Z.-C.; Landreth, C. C.; Adrian, R. J.; Hanratty, T. J. 1991: High resolution measurement of turbulent structure in a channel with particle image velocimetry. Exp. Fluids 10, 301–312CrossRefGoogle Scholar
  8. Westerweel, J.; Nieuwstadt, F. T. M. 1990: Measurement of dynamics of coherent flow structures using particle image velocimetry. Proc. Fifth Intl. Symp. on Applications of Laser Anemometry to Fluid Mechanics, Lisbon, 18.3Google Scholar
  9. Willert, C. E.; Gharib, M. 1991: Digital particle image velocimetry. Exp. Fluids 10, 181–193CrossRefGoogle Scholar

Copyright information

© Springer-Verlag 1992

Authors and Affiliations

  • A. K. Prasad
    • 1
  • R. J. Adrian
    • 1
  • C. C. Landreth
    • 1
  • P. W. Offutt
    • 1
  1. 1.Dept. of Theoretical and Applied MechanicsUniversity of IllinoisUrbanaUSA

Personalised recommendations