Diffusion-induced bias in near-wall velocimetry

Reza Sadr, Christel Hohenegger, Haifeng Li, Peter J. Mucha, Minami Yoda

Research output: Contribution to journalArticle

35 Citations (Scopus)

Abstract

The Brownian fluctuations of the colloidal tracers often used in microscale velocimetry are typically isotropic in the bulk. In the near-wall region, however, these fluctuations are strongly affected by the hydrodynamic interaction with the wall and by the no-flux condition imposed by the wall. These wall effects can, under appropriate conditions, bias measurements based on colloidal tracers, potentially leading to significant overestimation of near-wall velocities. We use a Fokker-Planck description to generate probability density functions of the distances from a single wall sampled by the matched particles that are present in the same window at both the start and end of a time interval. The importance of the resulting bias for experimental parameters is then quantified in terms of the size of the imaged region and measurement interval. We conclude with a brief discussion of the implications for near-wall velocimetry measurements.

Original languageEnglish
Pages (from-to)443-456
Number of pages14
JournalJournal of Fluid Mechanics
Volume577
DOIs
Publication statusPublished - 25 Apr 2007
Externally publishedYes

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Velocity measurement
Probability density function
Hydrodynamics
tracers
Fluxes
intervals
probability density functions
microbalances
hydrodynamics
interactions

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

Cite this

Diffusion-induced bias in near-wall velocimetry. / Sadr, Reza; Hohenegger, Christel; Li, Haifeng; Mucha, Peter J.; Yoda, Minami.

In: Journal of Fluid Mechanics, Vol. 577, 25.04.2007, p. 443-456.

Research output: Contribution to journalArticle

Sadr, Reza ; Hohenegger, Christel ; Li, Haifeng ; Mucha, Peter J. ; Yoda, Minami. / Diffusion-induced bias in near-wall velocimetry. In: Journal of Fluid Mechanics. 2007 ; Vol. 577. pp. 443-456.
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