Three-dimensional particle imaging with a single camera

Willert, Christian; Gharib, Morteza

doi:10.1007/bf00193880

Cited by 260 publications

(142 citation statements)

References 3 publications

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“…In order to analyse the three-dimensional dynamics of vortex rings such as the oval vortex ring and AR4 elliptical vortex ring considered in this study, three-dimensional velocimetry is required. The three-dimensional, threecomponent defocusing digital particle image velocimetry (DDPIV) technique (Willert & Gharib 1992;Pereira & Gharib 2002;Pereira et al 2006) has been applied successfully to non-axisymmetric vortex ring flows by Troolin & Longmire (2009) and Kim & Gharib (2011), and is a promising candidate for performing three-dimensional velocimetry measurements on vortex rigs undergoing large deformations.…”

Section: O'farrell and J O Dabirimentioning

confidence: 99%

Pinch-off of non-axisymmetric vortex rings

O’Farrell

Dabiri

2014

J. Fluid Mech.

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The formation and pinch-off of non-axisymmetric vortex rings is considered experimentally. Vortex rings are generated using a non-circular piston-cylinder arrangement, and the resulting velocity fields are measured using digital particle image velocimetry. Three different nozzle geometries are considered: an elliptical nozzle with an aspect ratio of two, an elliptical nozzle with an aspect ratio of four and an oval nozzle constructed from tangent circular arcs. The formation of vortices from the three nozzles is analysed by means of the vorticity and circulation, as well as by investigation of the Lagrangian coherent structures in the flow. The results indicate that, in all three nozzles, the maximum circulation the vortex can attain is determined by the equivalent diameter of the nozzle: the diameter of a circular nozzle of identical cross-sectional area. In addition, the time at which the vortex rings pinch off is found to be constant along the nozzle contours, and independent of relative variations in the local curvature. A formation number for this class of vortex rings is defined based on the equivalent diameter of the nozzle, and the formation number for vortex rings of the three geometries considered is found to lie in the range of 3-4. The implications of the relative shape and local curvature independence of the formation number on the study and modelling of naturally occurring vortex rings such as those that appear in biological flows is discussed.

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Section: O'farrell and J O Dabirimentioning

confidence: 99%

Pinch-off of non-axisymmetric vortex rings

O’Farrell

Dabiri

2014

J. Fluid Mech.

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“…This method was proposed by Willert and Gharib (1992) and applied for macroscopic two phase flow by Pereira et al (2000) and Pereira and Gharib (2002). A theoretical examination of the underlying optics for macroscopic applications was presented by Dabiri (2005, 2008).…”

Section: Defocused Imaging With Aperture (Three-pinhole Technique)mentioning

confidence: 99%

Particle imaging techniques for volumetric three-component (3D3C) velocity measurements in microfluidics

Cierpka

Kähler

2011

J Vis

131

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The reliable measurement of the 3D3C velocity field in microfluidic devices becomes more and more important for future optimization and developments for lab-on-a-chip applications or point-of-care medical diagnosis systems. In the past years, different particle-based imaging methods, such as confocal scanning microscopy, holography, stereoscopic and tomographic imaging or approaches based on defocused particle images or optical aberrations have been developed and applied successfully to measure velocity fields in microfluidic systems. The benefits and drawbacks of these methods will be discussed in detail as the proper understanding of the measurement principle is essential to select the most appropriate technique for a desired measurement application. Once an imaging method is chosen, the velocity can be estimated by correlation-based methods or tracking approaches. The advantages and disadvantages of both methods and the importance of image preprocessing will also be discussed in detail.

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“…Mass et al demonstrated 3d3c measurements with multiple cameras in 1993 [128,129]. The 3d3c tracking with a single camera was introduced by Willert and Gharib in 1992 by using defocussing in connection with a coding aperture that is a mask with three pinholes [130]. As a result, the depth information is extracted from the particle image.…”

Section: Space Measurementmentioning

confidence: 99%

Imaging Flow Velocimetry with Laser Mie Scattering

Fischer

2017

Applied Sciences

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Abstract:Imaging flow velocity measurements are essential for the investigation of unsteady complex flow phenomena, e.g., in turbomachines, injectors and combustors. The direct optical measurement on fluid molecules is possible with laser Rayleigh scattering and the Doppler effect. However, the small scattering cross-section results in a low signal to noise ratio, which hinders time-resolved measurements of the flow field. For this reason, the signal to noise ratio is increased by using laser Mie scattering on micrometer-sized particles that follow the flow with negligible slip. Finally, the ongoing development of powerful lasers and fast, sensitive cameras has boosted the performance of several imaging methods for flow velocimetry. The article describes the different flow measurement principles, as well as the fundamental physical measurement limits. Furthermore, the evolution to an imaging technique is outlined for each measurement principle by reviewing recent advances and applications. As a result, the progress, the challenges and the perspectives for high-speed imaging flow velocimetry are considered.

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Three-dimensional particle imaging with a single camera

Cited by 260 publications

References 3 publications

Pinch-off of non-axisymmetric vortex rings

Pinch-off of non-axisymmetric vortex rings

Particle imaging techniques for volumetric three-component (3D3C) velocity measurements in microfluidics

Imaging Flow Velocimetry with Laser Mie Scattering

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