Particle tracking velocimetry
Encyclopedia
Particle tracking velocimetry (PTV) is a velocimetry
method, i.e a technique to measure velocity of particles
. The name suggests that the particles are tracked, and not only recorded as an image as it is suggested in another form, particle image velocimetry
. There are two very different experimental methods:
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.
Velocimetry
Velocimetry is the measurement of the velocity of fluids, as often used to solve fluid dynamics problems, or to study fluid networks, as well as in industrial and process control applications, or in the creation of new kinds of fluid flow sensors...
method, i.e a technique to measure velocity of particles
Particle
A particle is, generally, a small localized object to which can be ascribed physical properties. It may also refer to:In chemistry:* Colloidal particle, part of a one-phase system of two or more components where the particles aren't individually visible.In physics:* Subatomic particle, which may be...
. The name suggests that the particles are tracked, and not only recorded as an image as it is suggested in another form, particle image velocimetry
Particle image velocimetry
Particle image velocimetry is an optical method of flow visualization used in education and research. It is used to obtain instantaneous velocity measurements and related properties in fluids...
. There are two very different experimental methods:
- the two dimensional (2D) modification of Particle Image VelocimetryParticle image velocimetryParticle image velocimetry is an optical method of flow visualization used in education and research. It is used to obtain instantaneous velocity measurements and related properties in fluids...
(PIV), in which the flow field is measured in the two-dimensional slice of the flow, illuminated by a laserLaserA laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
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, synchroniously 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 coherentCoherence (physics)
In physics, coherence is a property of waves that enables stationary interference. More generally, coherence describes all properties of the correlation between physical quantities of a wave....
or monochromatic and only its illuminance
Illuminance
In photometry, illuminance is the total luminous flux incident on a surface, per unit area. It is a measure of the intensity of the incident light, wavelength-weighted by the luminosity function to correlate with human brightness perception. Similarly, luminous emittance is the luminous flux per...
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 or 4 CCDs . A photograph of a 4 CCD system at ETH Zurich is shown below.Real time image processing schemes
- Real time image compression using a customized FPGA design, http://link.aip.org/link/?RSINAK/78/023704/1
- Real time image processing using a on-camera FPGA, http://adsabs.harvard.edu/abs/2010ExFl...48..105K
See also
- Particle image velocimetryParticle image velocimetryParticle image velocimetry is an optical method of flow visualization used in education and research. It is used to obtain instantaneous velocity measurements and related properties in fluids...
- Laser Doppler velocimetryLaser Doppler velocimetryLaser Doppler Velocimetry , also known as Laser Doppler Anemometry , is the technique of using the Doppler shift in a laser beam to measure the velocity in transparent or semi-transparent fluid flows, or the linear or vibratory motion of opaque, reflecting, surfaces.-Technology origin:With the...
- Hot-wire anemometry
- Molecular tagging velocimetryMolecular tagging velocimetryMolecular Tagging Velocimetry is a specific form of flow velocimetry, a technique for determining the velocity of currents in fluids such as air and water. In its simplest form, a single "write" laser beam is shot once through the sample space...
External links
- from "The Art of Laser Velocimetry", an explanation of PTV.
- Open Source particle tracking software in three dimensions 3D-PTV ETH Zurich/Tel Aviv University