Experiments in Fluids

, Volume 50, Issue 4, pp 787–798

PIV measurement of flow around an arbitrarily moving body

Research Article

Abstract

This paper presents a PIV (particle image velocimetry) image processing method for measuring flow velocities around an arbitrarily moving body. This image processing technique uses a contour-texture analysis based on user-defined textons to determine the arbitrarily moving interface in the particle images. After the interface tracking procedure is performed, the particle images near the interface are transformed into Cartesian coordinates that are related to the distance from the interface. This transformed image always has a straight interface, so the interrogation windows can easily be arranged at certain distances from the interface. Accurate measurements near the interface can then be achieved by applying the window deformation algorithm in concert with PIV/IG (interface gradiometry). The displacement of each window is evaluated by using the window deformation algorithm and was found to result in acceptable errors except for the border windows. Quantitative evaluations of this method were performed by applying it to computer-generated images and actual PIV measurements.

List of symbols

Ab

Average intensity of the boundary region

Ap

Average intensity of the particle region

Aavg

Offset value for adjusting the average value of T to zero

β

Bias error [pixels]

C

Correlation coefficient

I

Intensity field of the CCD recorded image

I′

Transformed intensity field in the regularized coordinates

L

Shooting distance in the prediction operation [pixels]

M (s, n)

Intensity map of the masking

P (Δ)

Probability function vertical to the inclined angle

θ

Inclined angle of the texton

ρ

Curvature radius of the interface [pixels]

ρp

Particle density of the synthetic images [particles/pixels2]

σ

Random error [pixels]

T (i, j, θ)

Single texton with an inclined angle θ

td

Width of the interface imposed by the Gaussian distribution

tw

Size of the square texton [pixels]

wx

Wall-parallel size of the interrogation window [pixels]

wy

Wall-normal size of the interrogation window [pixels]

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Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  1. 1.Department of Mechanical EngineeringKAISTYuseong-gu, DaejeonKorea

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