Particle Tracking Velocimetry Software

A certain part of this page is a mirror of the long existing but outdated web pages on the server of the Institute of Geodesy and Photogrammetry (IGP) here or the older version of H.-G. Maas [link]

Introduction

The three-dimensional particle tracking velocimetry (3D-PTV) is a nonintrusive measurement technique which allows for the determination of velocity and velocity derivatives in turbulent flows. It is based on the visualization of a flow seeded with small neutrally buoyant particles (flow tracers) and a stereoscopic recording image sequences of the particles. In the past decade the successful research work performed by the Institute of Geodesy and Photogrammetry (IGP) in cooperation with the Institute of Environmental Engineering (before 01.01.06 Institute of Hydromechanics and Water Resources Management, IHW) at ETH Zurich led to an operational and reliable measurement tool used in experimental fluid mechanics.  Recently further progress has been achieved in the improvement of the existing hard- and software solutions.

Experimental set up

Figure 1: Typical experimental set up of the four-camera 3D PTV system. An observation volume is illuminated by the CW laser collimated beam from below.

Figure 2: Four VGA (640 x 480 pixels) CCD cameras, 60 frames-per-second

The four-camera system in Figures 1 and 2 is uses two frame grabbers (Matrox Genesis)  to provide online digitization and storage of the images. The length of the recorded digital image sequences is restricted by the storage device capabilities. The data rate for a 60 Hz full-frame camera with a resolution of 640 x 480 pixel is about 19 MB/sec, and hence in an experiment which lasts for 1 minute four cameras deliver a total amount of about 4.5 GB image data.

A high-speed three-dimensional Particle Tracking Velocimetry System (3D-PTV)

Recently, the IfU purchased a unique recording system for high-speed 3D-PTV. There are two goals of this investment:

• There is an increasing interest of the Hydromechanics group in moderate and high Re_λ turbulent flows. Some recent experiments of the group, related to the stretching of Lagrangian material objects, the effect of dilute polymers and others are based on measurements at approximately Re_λ= 50. They could be repeated in higher Reynolds numbers flows. In addition, an ability to track fluid tracers that move at tens of centimeters per second will open a new field of research in the free shear and wall bounded turbulent flows.
• The major goal is to perform experiments in two-phase turbulent flows. This can be achieved by a combination of the ‘old’, 50Hz 3D-PTV system, shown in Fig.1 (e.g., Luethi et al. 2005, Guala et al, 2005, Liberzon et al, 2005a, 2005b) and the new, high-speed system. The combined system allows us to follow two types of particles simultaneously e.g. heavy and light particles, or heavy particles and flow tracers.

The system is based on four (4) high-speed CMOS cameras by Miktrotron (www.miktrotron.de) with 1280 x 1024 pixels, 10 bit, working at 500 fps. All four cameras are synchronized in a special way, with a maximum possible time jitter of 1/10 of the frame rate. The recording system is the only one of this type and includes the long-term streaming and storage of IO Industries (http://www.ioindustries.com), customized for our use by Cosyco (www.cosyco.de). The system includes 48 hard-disks and 4 special frame-grabbers that deliver the information directly to the array of disks.

Figure 3: Four high-speed CMOS cameras of 1024 x 1008 pixels, 10 bit, 500 frames-per-second.

Figure 4: Back and front sides of the real-time high-speed recording and storage streaming system (650 Mb/sec, 4 CFLC acquisition cards, 48 hard drives).

Some key publications by subjects:

Multi-image matching:

Maas, H.-G., 1992: Complexity analysis for the determination of image correspondences in dense spatial target fields. International Archives of Photogrammetry and Remote Sensing, Vol. 29, Part B5, pp. 102-107
http://www.tu-dresden.de/fghgipf/forschung/material/publ_maas/isprs92_ambig.pdf

Multimedia geometry:

Maas, H.-G., 1995: New developments in multimedia photogrammetry. Optical 3-D Measurement Techniques III (Eds.: A. Grün, H. Kahmen), Wichmann Verlag, Karlsruhe
http://www.tu-dresden.de/fghgipf/forschung/material/publ_maas/O3D95_multimed.pdf

Image processing, 3D coordinate determination:

Maas, H.-G., Grün, A., Papantoniou, D., 1993: Particle tracking in threedimensional turbulent flows - Part I: Photogrammetric determination of particle coordinates. Exp. Fluids Vol. 15, pp. 133-146.
Maas, H.-G., Grün, A., 1995: Digital photogrammetric techniques for high-resolution 3-D flow velocity measurements. Optical Engineering Vol. 34, No. 7, pp. 1970-1976

Image processing, calibration, multi-image matching, 3D coordinate determination:

Maas, H.-G., 1992: Digitale Photogrammetrie in der dreidimensionalen Strömungsmesstechnik. ETH Zürich - Dissertation Nr. 9665, Schriftenreihe des Instituts für Geodäsie und Photogrammetrie, Nr. 50
http://www.tu-dresden.de/fghgipf/forschung/material/publ_maas/Maas_Diss.pdf

Applications:

Stüer, H., Maas, H.-G., Virant, M., Becker, J., 1999: A volumetric 3D measurement tool for velocity field diagnostics in microgravity experiments. Measurement Science and Technology, Vol. 10, pp. 904-913.
Maas, H.-G., Virant, M., Becker, J., Bösemann, W., Gatti, L., Henrichs, A., 2002: Photogrammetric methods for measurements in fluid physics experiments in space. Acta Astronautica, Vol. 50/4, pp. 225-231.

Longer list of publications in chronological order:

1. Beat Lüthi, Arkady Tsinober, Wolfgang Kinzelbach, 2005 "Lagrangian measurement of vorticity dynamics in turbulent flow", Journal of Fluid Mechanics, Volume 528. April 2005. pp. 87-118
2. Dissertation Beat Lüthi, 2003 "Some aspects of strain, vorticity, and material element dynamics as measured with 3D particle tracking velocimetry in a turbulent flow"
   Diss., Technische Wissenschaften ETH Zürich, Nr. 14893, 2003
   Abstract: http://e-collection.ethbib.ethz.ch/show?type=diss&nr=14893&part=abstracts
   Full text: http://e-collection.ethbib.ethz.ch/show?type=diss&nr=14893&part=fulltext (11Mb)
3. Dissertation Jochen Willneff, 2003
   A Spatio-Temporal Matching Algorithm for 3D Particle Tracking Velocimetry
   Diss., Technische Wissenschaften ETH Zurich, Nr. 15276, Zurich, Switzerland, 2003
   Abstract:  <http://www.photogrammetry.ethz.ch/research/diss/DissETH15276abstract.pdf> (24KB)
   Full Text:  <http://www.photogrammetry.ethz.ch/research/diss/DissETH15276.pdf> (13MB)
   
4. Jochen Willneff, Beat Lüthi, 2003:
   Particle Tracking Velocimetry measurements for Lagrangian analysis of turbulent flows
   Optical 3-D Measurement Techniques VI, Vol. II, p. 191-198, Zurich, Switzerland, 22.-26. September 2003
   Full Text: <http://www.photogrammetry.ethz.ch/research/ptv/optical3d2003.pdf> (185KB)
   
5. Jochen Willneff, 2002 "3D Particle Tracking Velocimetry based on image and object space information" ISPRS Commission V Symposium,  Corfu, Greece, September 2-6, 2002 Full Text:  <http://www.photogrammetry.ethz.ch/research/ptv/corfu2002.pdf> (1.1MB)
   
6. Jochen Willneff, Armin Gruen, 2002 "A new spatio-temporal matching algorithm for 3D-Particle Tracking Velocimetry ", The 9th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery Honolulu, Hawaii, USA, February 10-14, 2002 Full Text: <http://www.photogrammetry.ethz.ch/research/ptv/fd026.pdf> (0.7MB)
   
7. Stüer, H., J. Willneff, H.-G. Maas, 2000 "The impact of image compression on three-dimensional particle tracking velocimetry data", Journal of Flow Visualization and Image Processing (Publisher: Begell House), Vol.7 (2), pp.89-104
   
8. J. Willneff, H.-G. Maas, 2000, "Design and calibration of a four-headed camera system for use in microgravity research", International Archives of Photogrammetry and Remote Sensing, XIXth  ISPRS Congress Amsterdam 2000 Volume XXXIII, Part B5/2, Comission V, pp 894-899, 16-23 July 2000, Amsterdam, The Netherlands
   Full Text: <http://www.photogrammetry.ethz.ch/research/ptv/amsterdam.pdf> (331KB)
   
9. O. Dupont, F. Dubois, A. Vedernikov, J.-C. Legros, J. Willneff, C. Lockowandt, 1999 "Photogrammetric set-up for the analysis of particle motion in aerosol under microgravity conditions",Measurement Science and Technology, Volume 10, Number 10, October 1999, Special Issue: Instrumentation and Diagnostics for Microgravtiy Experiments, pp 921-933   
   Full Text: <http://www.photogrammetry.ethz.ch/research/ptv/jet.pdf> (688KB)
   
10. Lockowandt, C., Löth, K., Nilsson, J., Ranebo, H., Jofs, B., Schneider, H., Willneff, J., Dupont, O., Vedernikov, A., Legros, J.C., 1999 "The JET Module, A Tool for Aerosol Particle Experiments in  Microgravity" 50th International Astronautical Federation Congress, Microgravity Sciences and Processes Symposium, IAF-99-J.5.07, Amsterdam, October 1999, Full Text: <http://www.photogrammetry.ethz.ch/research/ptv/iaf99.pdf> (72KB)
    
11. Stueer, H., Willneff J., Maas H.-G., 1999 "Evaluation of image compression in 3D PTV", Videometrics VI, Proceeding of SPIE, San Jose, California, 1999, Vol. 3641, pp 228-238
    Full Text: <http://www.photogrammetry.ethz.ch/research/ptv/video99.pdf> (543KB)
    
12. Maas, H.-G., Gruen, A., Papantoniou, D., 1993, "Particle Tracking in threedimensional turbulent flows - Part I: Photogrammetric determination of particle coordinates", Experiments in Fluids Vol. 15, pp. 133-146
    
13. Malik, N., Dracos, T., Papantoniou, D., 1993, "Particle Tracking in threedimensional turbulent flows - Part II:  Particle tracking" ,Experiments in Fluids Vol. 15, pp. 279-294
14. Maas, H.-G., 1992, "Digitale Photogrammetrie in der dreidimensionalen Stroemungsmesstechnik", ETH Zurich - Dissertation Nr. 9665
15. Maas, H.-G., 1992, "Complexity analysis for the determination of image correspondences in dense spatial target fields",International Archives of Photogrammetry and Remote Sensing, Vol. XXIX, Part B5, pp. 102-107
    Full Text: <http://www.photogrammetry.ethz.ch/research/ptv/ambig.paper.ps.gz>
16. Maas, H.-G., 1991 "Digital Photogrammetry for Determination of Tracer Particle Coordinates in Turbulent Flow Research" Photogrammetric Engineering & Remote Sensing Vol. 57, No. 12, pp. 1593-1597
17. Papantoniou, D., Maas, H.-G. 1990. Recent advances in 3-D particle tracking velocimetry, Proc. 5^th. Int. Symp. On Appl. Of Laser Techs in Fluid Mech., Lisbon.
18. Papantoniou, D. Dracos, Th. 1990a. Analysing 3-D turbulent motions in open channel flow by use of stereoscopy and particle tracking. Advance in Turbulence, 2, Springer Berlin, 278-285.
19. Papantoniou, D. Dracos, Th. 1990b. Lagrangian statistics in open channel flow by 3-D particle tracking velocimetry, Eng. Turb. Model Expt., ed. Rodi & Garnic, Elsevier, 315-324.
20. Papantoniou, D. 1989, 3-D Particle tracking code, Internal report, Institute of Hydromechanics and Water Resources Management (IHW), Swiss Federal Institute of Technology, ETH Zurich (note: IHW is IFU from January 1st, 2006)

In addition, in 1996, IHW and IGP have organized a Short Course on "Three-Dimensional Velocity and Vorticity Measuring and Image Analysis Techniques". The lectures of this course (including those of Th. Dracos, A. Grün, H.-G. Maas, among the others) were published as ERCOFTAC Series Vol. 4, by Kluwer Academic Publishers.  The book  (ISBN: 0-7923-4256-9) is available from Springer (that acquired Kluwer) or from Amazon (including a search-in option).

The relevant part of table of contents:

III: Particle Tracking Velocimetry.

Particle Tracking Velocimetry (PTV), Basic Concepts; T. Dracos.

Videogrammetry: Methodology and PTV/LIF Applications; A. Grün.

Contributions of Digital Photogrammetry to 3-D PTV; H.-G. Maas.

Particle Tracking in Three-Dimensional Space; T. Dracos.

Establishment of a Videogrammetric PTV System; M. Virant, T. Dracos.

Example projects:

• The software development project on ETH research database [link]
  
• Velocity derivatives in turbulent flow from 3D-PTV measurements [link]
• Turbulent entrainment via PTV [link]
• Derivative of PTV - Scanning Particle Tracking Velocimetry [link]
• Turbulent flows of dilute polymers [link]
• Three dimensional flow measurements for biomedical applications: aneurysm and brain ventricle [link]
  
• JET growth motion in aerosols module observed under micro-gravity conditions on the sounding rocket MASER 8
• Study on the applicability of 3-D PTV to surface tension driven convection (Marangoni convection) joined project with ESA-ESTEC and Alenia Aerospazio [link]
  
• Study on the applicability of 3-D PTV for measurements in liquid columns (joined project with ESA-ESTEC and Alenia Aerospazio)

3D-PTV software

The Particle Tracking Velocimetry software performs the following tasks:

• Calibration of the multi-camera system (determination of camera exterior and interior orientations, lens distortion and further disturbances) and the exact geometric modelling ("multimedia geometry" - each beam from a particle to the sensor passes the three optical media water, glass, air with different refractive indices, which leads to a twice broken beam).
• Image preprocessing: perform highpass filtering due to non-uniformities in the background illumination
• Detect particles in the images by a modified thresholding operator, localize particles with subpixel accuracy by a centroid operator
• Establish stereoscopic correspondences
• Determine 3-D particle coordinates
• Storage of all relevant object and image space information
• Perform tracking in 2-D image and 3-D object space

A crucial point is the handling of ambiguities occuring in different steps of image  and data processing:

• Particles may overlap in the images. For that reason a modified thresholding/centroid operator was developed searching for local maxima in the images and dividing particle images at local minima under certain conditions.
• Due to the fact that particle images cannot be distinguished by features like size, shape or color, the only criterion for the establishment of stereoscopic correspondences is the epipolar line. Ambiguities occur when multiple candidates are found in a search area defined by the epipolar line. These ambiguities can only be solved if a third (or even a fourth) camera is being used.
• Ambiguities may also occur in the tracking procedure. Criteria like local correlation and smoothness of the velocity field are employed to solve these criteria.

News - the software is an open source for academic use

Particle Tracking Velocimetry software, developed by IGP/IFU, is available as  open-source software for academic use (no warranty, as it is). Anyone, who’s interested to use the software, should fill the form on the ordering page. To process your order, we need your contact details, the institution name, the contact address and a short research project description. Most important is valid and working e-mail account, to which the login information for downloading the package will be sent.

The software package includes some documentation files but users could also ask for some help (that would be provided on voluntary, free-time basis) from the members of Hydromechanics group of IfU or of Photogrammetry group at IGP. In general, both insitutes are interested in collaboration in various fields of fluid mechanics and photogrammetric research. We also encourage our users to develop the 3D-PTV further and ask (in the license agreement) to include their developments in the future versions of the PTV software.

News (June 2006)  - Ph.D position

TU Eindhoven (Dept. Mechanical Engineering, TU/e) is looking for a Ph.D., to work on experimental and theoretical analysis of the wake dynamics behind a heated cylinder. Short introduction is on this page, more details is on our wiki (restricted registration to the licensed users of 3D-PTV) or on the website of the TU/e