Digital Particle Image Velocimetry

doi:10.1007/BF00190388

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Digital Particle Image Velocimetry

Journal Article•DOI•

Digital Particle Image Velocimetry

Christian Willert¹, Morteza Gharib¹•Institutions (1)

University of California, San Diego¹

01 Jan 1991-Experiments in Fluids (Springer)-Vol. 10, Iss: 4, pp 181-193

TL;DR: In this article, the directional ambiguity associated with PIV and LSV is resolved by implementing local spatial cross-correlations between two sequential single-exposed particle images, and the recovered velocity data are used to compute the spatial and temporal vorticity distribution and the circulation of the vortex ring.

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Abstract: Digital particle image velocimetry (DPIV) is the digital counterpart of conventional laser speckle velocitmetry (LSV) and particle image velocimetry (PIV) techniques. In this novel, two-dimensional technique, digitally recorded video images are analyzed computationally, removing both the photographic and opto-mechanical processing steps inherent to PIV and LSV. The directional ambiguity generally associated with PIV and LSV is resolved by implementing local spatial cross-correlations between two sequential single-exposed particle images. The images are recorded at video rate (30 Hz or slower) which currently limits the application of the technique to low speed flows until digital, high resolution video systems with higher framing rates become more economically feasible. Sequential imaging makes it possible to study unsteady phenomena like the temporal evolution of a vortex ring described in this paper. The spatial velocity measurements are compared with data obtained by direct measurement of the separation of individual particle pairs. Recovered velocity data are used to compute the spatial and temporal vorticity distribution and the circulation of the vortex ring.

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Journal Article•DOI•

Two-dimensional digital image correlation for in-plane displacement and strain measurement: a review

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Bing Pan¹, Kemao Qian¹, Huimin Xie², Anand Asundi¹•Institutions (2)

Nanyang Technological University¹, Tsinghua University²

27 Apr 2009-Measurement Science and Technology

TL;DR: In this article, a review of the 2D digital image correlation (2D DIC) technique for displacement field measurement and strain field estimation is presented, and detailed analyses of the measurement accuracy considering the influences of both experimental conditions and algorithm details are provided.

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Abstract: As a practical and effective tool for quantitative in-plane deformation measurement of a planar object surface, two-dimensional digital image correlation (2D DIC) is now widely accepted and commonly used in the field of experimental mechanics. It directly provides full-field displacements to sub-pixel accuracy and full-field strains by comparing the digital images of a test object surface acquired before and after deformation. In this review, methodologies of the 2D DIC technique for displacement field measurement and strain field estimation are systematically reviewed and discussed. Detailed analyses of the measurement accuracy considering the influences of both experimental conditions and algorithm details are provided. Measures for achieving high accuracy deformation measurement using the 2D DIC technique are also recommended. Since microscale and nanoscale deformation measurement can easily be realized by combining the 2D DIC technique with high-spatial-resolution microscopes, the 2D DIC technique should find more applications in broad areas.

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2,530 citations

Journal Article•DOI•

PIVlab – Towards User-friendly, Affordable and Accurate Digital Particle Image Velocimetry in MATLAB

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William Thielicke¹, Eize Stamhuis¹•Institutions (1)

Bremen University of Applied Sciences¹

16 Oct 2014-Journal of open research software

TL;DR: The accuracy of several algorithms was determined and the best performing methods were implemented in a user-friendly open-source tool for performing DPIV flow analysis in Matlab.

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Abstract: Digital particle image velocimetry (DPIV) is a non-intrusive analysis technique that is very popular for mapping flows quantitatively. To get accurate results, in particular in complex flow fields, a number of challenges have to be faced and solved: The quality of the flow measurements is affected by computational details such as image pre-conditioning, sub-pixel peak estimators, data validation procedures, interpolation algorithms and smoothing methods. The accuracy of several algorithms was determined and the best performing methods were implemented in a user-friendly open-source tool for performing DPIV flow analysis in Matlab.

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1,783 citations

Journal Article•DOI•

Fundamentals of digital particle image velocimetry

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Jerry Westerweel¹•Institutions (1)

Delft University of Technology¹

01 Dec 1997-Measurement Science and Technology

TL;DR: In this paper, the measurement principle of digital particle image velocimetry (PIV) is described in terms of linear system theory and conditions for PIV correlation analysis as a valid interrogation method are determined.

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Abstract: The measurement principle of digital particle image velocimetry (PIV) is described in terms of linear system theory. The conditions for PIV correlation analysis as a valid interrogation method are determined. Limitations of the method arise as consequences of the implementation. The theory is applied to investigate the statistical properties of the analysis and to optimize and improve the measurement performance. The theoretical results comply with results from Monte Carlo simulations and test measurements described in the literature. Examples of both correct and incorrect implementations are given.

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1,427 citations

Cites background from "Digital Particle Image Velocimetry"

...However, nowadays PIV has developed towards the use of electronic cameras for direct recording of the particle images (Willert and Gharib 1991)....
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...The Gaussian peak fit is based on the notion that the displacement-correlation peak has an approximately Gaussian shape: ̂G = lnR∗−1− lnR∗+1 2(lnR∗−1+ lnR∗+1− 2 lnR∗0) (48) (Willert and Gharib 1991)....
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Journal Article•DOI•

Twenty years of particle image velocimetry

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Ronald J. Adrian¹, Ronald J. Adrian²•Institutions (2)

Arizona State University¹, University of Illinois at Urbana–Champaign²

06 Jul 2005-Experiments in Fluids

TL;DR: The development of the method of particle image velocimetry (PIV) is traced by describing some of the milestones that have enabled new and/or better measurements to be made.

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Abstract: The development of the method of particle image velocimetry (PIV) is traced by describing some of the milestones that have enabled new and/or better measurements to be made. The current status of PIV is summarized, and some goals for future advances are addressed.

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1,284 citations

Cites background from "Digital Particle Image Velocimetry"

...But, in the early 1990s, several investigators, most notably Willert and Gharib (1991) and Westerweel (1993), published results indicating that the low resolution of digital cameras was not as serious an issue as others had supposed, and that digital PIV could be accurate enough to provide useful results....
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Journal Article•DOI•

Oscillating foils of high propulsive efficiency

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J. M. Anderson¹, K. Streitlien¹, David S. Barrett¹, Michael S. Triantafyllou¹•Institutions (1)

Massachusetts Institute of Technology¹

10 Apr 1998-Journal of Fluid Mechanics

TL;DR: In this article, the phase angle between transverse oscillation and angular motion is the critical parameter affecting the interaction of leading-edge and trailing-edge vorticity, as well as the efficiency of propulsion.

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Abstract: Thrust-producing harmonically oscillating foils are studied through force and power measurements, as well as visualization data, to classify the principal characteristics of the flow around and in the wake of the foil. Visualization data are obtained using digital particle image velocimetry at Reynolds number 1100, and force and power data are measured at Reynolds number 40 000. The experimental results are compared with theoretical predictions of linear and nonlinear inviscid theory and it is found that agreement between theory and experiment is good over a certain parametric range, when the wake consists of an array of alternating vortices and either very weak or no leading-edge vortices form. High propulsive efficiency, as high as 87%, is measured experimentally under conditions of optimal wake formation. Visualization results elucidate the basic mechanisms involved and show that conditions of high efficiency are associated with the formation on alternating sides of the foil of a moderately strong leading-edge vortex per half-cycle, which is convected downstream and interacts with trailing-edge vorticity, resulting eventually in the formation of a reverse Karman street. The phase angle between transverse oscillation and angular motion is the critical parameter affecting the interaction of leading-edge and trailing-edge vorticity, as well as the efficiency of propulsion.

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1,209 citations

Cites methods from "Digital Particle Image Velocimetry"

...DPIV velocity data for the foil at its maximum heave position, and (a) St = 0.30, StTE = 0.36, h◦/c = 0.25, θ = 15 ◦, αmax = 28.3 ◦, ψ = 90◦; (b) StTE = 0.36, h◦/c = 0.75, θ = 30 ◦, αmax = 15 ◦, ψ = 90◦; (c) St = StTE = 0.36, h◦/c = 0.75, θ = 30 ◦, αmax = 20.4 ◦, ψ = 75◦; (d) StTE = 0.36, h◦/c = 0.75, θ = 30 ◦, αmax = 20.2 ◦, ψ = 105◦....
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...In order to investigate the features of the flow around a oscillating foil and associate them with the measured force characteristics, visualization experiments were conducted (Anderson 1996) at smaller scale using digital particle image velocimetry (DPIV) (Willert & Gharib 1991)....
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...The agreement in thrust coefficient between the two sets of experiments is good considering the approximate methodology used with the DPIV data....
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...The DPIV plane view was 22 cm long in the direction of foil motion and 15 cm wide....
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...Average thrust estimates based on the DPIV data (Reynolds number 1100) confirm the trends established by the force and power experiments at Reynolds number 40 000....
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References

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Book•

Digital Picture Processing

[...]

Azriel Rosenfeld, Avinash C. Kak

01 Jan 1976

TL;DR: The rapid rate at which the field of digital picture processing has grown in the past five years had necessitated extensive revisions and the introduction of topics not found in the original edition.

...read moreread less

Abstract: The rapid rate at which the field of digital picture processing has grown in the past five years had necessitated extensive revisions and the introduction of topics not found in the original edition.

...read moreread less

4,231 citations

Journal Article•DOI•

On the formation of vortex rings: Rolling-up and production of circulation

[...]

Norbert Didden¹•Institutions (1)

Max Planck Society¹

01 Jan 1979-Zeitschrift für Angewandte Mathematik und Physik

TL;DR: In this article, the authors investigated the temporal development of the rolling-up process of vortex rings produced in water at a circular nozzle by flow visualization and compared the results with similarity laws for the rolling up of vortex sheets in plane flow.

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Abstract: The temporal development of the rolling-up process of vortex rings produced in water at a circular nozzle is investigated by flow visualization. The results are compared with similarity laws for the rolling-up of vortex sheets in plane flow. The unsteady flow field in the nozzle-exit plane is measured by laser anemometry. The vorticity distribution in the boundary layers at the inner and outer nozzle wall and the vorticity flux through the exit plane are derived from the measurements. The flow conditions measured at the nozzle are used to explain the production of the ring-vortex circulation (measured three nozzle-diameters downstream) in relation to the generation conditions.

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386 citations

"Digital Particle Image Velocimetry" refers background in this paper

...This observation was already reported by Didden (1979) and Glezer (1981)....
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Journal Article•DOI•

Scattering particle characteristics and their effect on pulsed laser measurements of fluid flow: Speckle velocimetry vs particle image velocimetry

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Ronald J. Adrian¹•Institutions (1)

University of Illinois at Urbana–Champaign¹

01 Jun 1984-Applied Optics

TL;DR: The source density for a fluid volume illuminated by a laser sheet of thickness Δz is defined to be the number density of particles per unit volume and their size can vary over a very wide range of values, depending upon the fluid and its treatment.

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Abstract: Multiple-exposure recording of the speckle pattern trans lation that occurs during surface motion has been used ex tensively to measure in-plane displacements of solid surfaces. The application of this technique and derivative methods to the measurement of 2-D fluid velocity fields is of current in terest to experimentalists in fluid mechanics. Applications involving fluids are fundamentally different from those involving solids in several regards. One of the most important is that the light scattering characteristics of fluids containing small particles can be quite unlike those of solid surfaces. For example, fluids are illuminated by a pulsed sheet of laser light whose thickness is Δz. Hence scattering occurs from a volume distribution of particle scattering sites rather than a surface distribution. The particles are typically small (0.1-10 μm), and they act as discrete point sources of scattered light. Most important, from the viewpoint of this Letter, the number density of particles per unit volume and their size can vary over a very wide range of values, depending upon the fluid and its treatment. For speckle patterns to exist, the number of scattering sites per unit volume must be so high that many images overlap with random phase in the image plane. Since the number densities of scatterers in fluids can be quite low, it is possible that speckle will not be present in many fluid applications, and discrete images of particles will be photographed instead. This will change the mode of operation from laser speckle velocimetry to particle image velocimetry, as discussed in Ref. 4. Following Ref. 4, we will define the source density for a fluid volume illuminated by a laser sheet of thickness Δz to be

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317 citations

"Digital Particle Image Velocimetry" refers background in this paper

...However, as Adrian (1984) argues, in most practical cases low seeding densities exist, which results in the imaging of individual particles, and the technique is then referred to as PIV....
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Journal Article•DOI•

Multi-point optical measurements of simultaneous vectors in unsteady flow—a review

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Ronald J. Adrian¹•Institutions (1)

University of Illinois at Urbana–Champaign¹

01 Jun 1986-International Journal of Heat and Fluid Flow

TL;DR: Optical techniques for measuring large numbers of simultaneous velocity vectors in two-and three-dimensional regions of fluid flows are reviewed in this article, which provides spatial information of the type that is available from flow visualization with accuracy approaching that of single-point methods such as laser Doppler velocimetry and hot wire.

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268 citations

"Digital Particle Image Velocimetry" refers methods in this paper

...PIV has also been applied in numerous fluids experiments such as the turbulent wake of a cylinder (Kompenhans and Reichmuth 1987; Lourenco and Krothapalli 1987), the flow around cavitation bubbles (Vogel and Lauterborn 1988), the flow behind an impulsively started airfoil (Lourenco et al. 1986), and jets in water (Adrian 1986 a). An excellent review of these two spatial velocimetry techniques and similar methods is given by Adrian (1986b) ....
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Journal Article•DOI•

Image shifting technique to resolve directional ambiguity in double-pulsed velocimetry

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Ronald J. Adrian¹•Institutions (1)

University of Illinois at Urbana–Champaign¹

01 Nov 1986-Applied Optics

TL;DR: Image shifting provides a method of determining the direction of displacement, and hence the velocity, for all types of pulsed laser velocimeter, and it is capable of high performance.

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Abstract: Image shifting provides a method of determining the direction of displacement, and hence the velocity, for all types of pulsed laser velocimeter. It is independent of the scattering properties of the particles and/or the intensity of the illumination of the first image with respect to the second image, and it is capable of high performance. With rotating mirror systems, image shifting can be used to offset negative velocities up to 10 m/s. With electrooptic systems, it is estimated that image shifting can be used at velocities up to 500 m/s.

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265 citations

"Digital Particle Image Velocimetry" refers methods in this paper

...To avoid this problem, image shifting ( Adrian 1986a; Landreth and Adrian 1988) may be applied during the image capture....
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...This means that overlapping particles in a low velocity region of the flow cannot yield velocity vectors unless an image shifting technique is used ( Adrian 1986a; Landreth and 182 Experiments in Fluids 10 (1991)...
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