Impact of hindered Brownian diffusion on the accuracy of particle-image velocimetry using evanescent-wave illumination

Reza Sadr, Haifeng Li, Minami Yoda

Research output: Contribution to journalArticle

47 Citations (Scopus)


The "nano-particle image velocimetry" technique uses evanescent-wave illumination generated by total internal reflection at the wall to excite colloidal neutrally buoyant fluorescent tracer particles. The displacement of these particles over time as they are convected by the flow then gives the flow velocity components tangential to the wall. Since the extent of the illumination region normal to the wall is comparable to the particle diameter, a major source of error in this technique is particle "mismatch" within a pair of images due to Brownian diffusion causing a particle to move in to or out of the illuminated region. The "brightness" (proportional to the amount of imaged fluorescence) and size of individual particle images in nPIV data are discussed. A sequence of artificial nPIV images are generated for a known uniform velocity field with the particles subject to hindered Brownian diffusion. The velocity fields calculated from these artificial images are compared with the known velocity field to determine the effect of Brownian diffusion-induced particle mismatch on nPIV accuracy. A similar analysis is carried out for experimental nPIV images. The results provide design guidance for experimental measurements using the nPIV technique.

Original languageEnglish
Pages (from-to)90-98
Number of pages9
JournalExperiments in Fluids
Issue number1
Publication statusPublished - Jan 2005
Externally publishedYes


ASJC Scopus subject areas

  • Computational Mechanics
  • Mechanics of Materials
  • Physics and Astronomy(all)
  • Fluid Flow and Transfer Processes

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