Experiments in Fluids

, Volume 42, Issue 2, pp 225–240 | Cite as

Intensity Capping: a simple method to improve cross-correlation PIV results

Research Article


A common source of error in particle image velocimetry (PIV) is the presence of bright spots within the images. These bright spots are characterized by grayscale intensities much greater than the mean intensity of the image and are typically generated by intense scattering from seed particles. The displacement of bright spots can dominate the cross-correlation calculation within an interrogation window, and may thereby bias the resulting velocity vector. An efficient and easy-to-implement image-enhancement procedure is described to improve PIV results when bright spots are present. The procedure, called Intensity Capping, imposes a user-specified upper limit to the grayscale intensity of the images. The displacement calculation then better represents the displacement of all particles in an interrogation window and the bias due to bright spots is reduced. Four PIV codes and a large set of experimental and simulated images were used to evaluate the performance of Intensity Capping. The results indicate that Intensity Capping can significantly increase the number of valid vectors from experimental image pairs and reduce displacement error in the analysis of simulated images. A comparison with other PIV image-enhancement techniques shows that Intensity Capping offers competitive performance, low computational cost, ease of implementation, and minimal modification to the images.



The authors are grateful for the discussions with J. Rosman, J. Koseff, and S. Monismith and the technical help provided by R. Gurka and R. Rosenzweig. The authors extend special thanks to M. Wernet for implementing his SPOF technique. The authors would like to acknowledge contributions to the Ocean PIV project by J. Jaffe, P. Roberts, F. Simonet, P. Franks, S. Monismith, C. Troy, and A. Horner-Devine. Support for Ocean PIV was provided by NSF grant OCE-0220213. R. Lowe acknowledges support from NSF grant OCE-0453117.


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Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  • Uri Shavit
    • 1
  • Ryan J. Lowe
    • 2
  • Jonah V. Steinbuck
    • 2
  1. 1.Civil and Environmental Engineering, TechnionHaifaIsrael
  2. 2.Environmental Fluid Mechanics LaboratoryStanford UniversityStanfordUSA

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