Particle tracking velocimetry

Particle Tracking Velocimetry (PTV) is a velocimetry method i.e. a technique to measure velocity of particles that are resident in a fluid. As the name suggests, individual particles are tracked, so this technique is a Lagrangian approach. In contrast to Particle Image Velocimetry (PIV), which is an Eulerian method that measures the velocity field of a fluid at a (rectangular) grid. There are two very different experimental methods:

• the two-dimensional (2D) PTV, in which the flow field is measured in the two-dimensional slice of the flow, illuminated by a laser sheet (a thin plane) and low density of seeded particles allow for the tracking each of them individually for several frames.
• the Three-Dimensional Particle tracking velocimetry (3D-PTV) is a distinctive experimental technique, based on multiple camera-system, three-dimensional volume illumination and tracking of flow tracers (i.e. particles) in three-dimensional space by using photogrammetric principles.

Description

A typical installation of the 3D-Particle tracking velocimetry consists of three or four digital cameras, installed in an angular configuration, synchronously recording the diffracted or fluorescent light from the flow tracers, seeded in the flow. The flow is illuminated by a collimated laser beam, or by another source of light. There is no restriction on the light to be coherent or monochromatic and only its illuminance has to be sufficient to illuminate the observational volume. Particles or tracers could be fluorescent, diffractive, tracked through as many as possible consecutive frames on as many cameras as possible. In principle, two cameras in the stereoscopic configuration are sufficient in order to determine the three coordinates of a particle in space, but in most practical situations, three or four cameras are necessary.

3D-PTV schemes

Several versions of 3D-PTV schemes exist. Most of these utilize either 3 CCDs ^[1] or 4 CCDs.^[2] A photograph of a 4 CCD system at ETH Zurich is shown below.

Real time image processing schemes

1. Real time image compression using a customized FPGA design, http://link.aip.org/link/?RSINAK/78/023704/1
2. Real time image processing using an on-camera FPGA, http://adsabs.harvard.edu/abs/2010ExFl...48..105K

See also

• Particle image velocimetry
• Laser Doppler velocimetry
• Hot-wire anemometry
• Molecular tagging velocimetry

References

1. ↑ 3D Particle Tracking Velocimetry Method: Advances and Error Analysis
2. ↑ 3-D Particle Tracking Velocimetry

• Maas, H.-G., 1992. Digitale Photogrammetrie in der dreidimensionalen Strömungsmesstechnik, ETH Zürich Dissertation Nr. 9665
• Malik, N., Dracos, T., Papantoniou, D., 1993. Particle Tracking in three dimensional turbulent flows - Part II: Particle tracking. Experiments in Fluids Vol. 15, pp. 279–294
• Maas, H.-G., Grün, A., Papantoniou, D., 1993. Particle Tracking in three dimensional turbulent flows - Part I: Photogrammetric determination of particle coordinates. Experiments in Fluids Vol. 15, pp. 133–146
• Srdic, Andjelka, 1998. Interaction of dense particles with stratified and turbulent environments. Ph.D. Dissertation, Arizona State University.
• Lüthi, B., Tsinober, A., Kinzelbach W. (2005)- Lagrangian Measurement of Vorticity Dynamics in Turbulent Flow. Journal of Fluid Mechanics. (528), p. 87-118
• Nicholas T. Ouellette, Haitao Xu, Eberhard Bodenschatz, A quantitative study of three-dimensional Lagrangian particle tracking algorithms, Experiments in Fluids, Volume 40, Issue 2, Feb 2006, Pages 301 - 313.
• Kreizer Mark, Ratner David and Alex Liberzon Real-time image processing for particle tracking velocimetry, Experiments in Fluids, Volume 48, Issue 1, pp. 105–110, http://adsabs.harvard.edu/abs/2010ExFl...48..105K

External links

• OpenPTV - Open Source Particle Tracking Velocimetry collaboration
• from "The Art of Laser Velocimetry", an explanation of PTV.
• "3D-PTV" - open source particle tracking velocimetry software in 3D ETH Zurich/Tel Aviv University