1 / 25

Volumetric 3-Component Velocimetry (V3V)

Volumetric 3-Component Velocimetry (V3V). Volumetric 3-Component Velocimetry (V3V). Individual laser pulses illuminate a volumetric measurement region 3-aperture camera probe captures images of tracer particle locations at each laser pulse, through each imaging aperture.

zody
Télécharger la présentation

Volumetric 3-Component Velocimetry (V3V)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Volumetric 3-Component Velocimetry (V3V)

  2. Volumetric 3-Component Velocimetry (V3V) • Individual laser pulses illuminate a volumetric measurement region • 3-aperture camera probe captures images of tracer particle locations at each laser pulse, through each imaging aperture • 3-dimensional particle positions are calculated based on information from each aperture • Flow velocity is measured based on individual particle displacements in the time between laser pulses

  3. V3V Operation • 3D3C Imaging Technique • Based on DDPIV (Gharib – Caltech) • Illumination • Laser illuminates tracers in a volume up to 140 x 140 x 100 mm • 2 pulses (like PIV) • 3D Camera • 3 apertures view measurement region from 3 different perspectives • 3D particle locations determined based on information from each aperture • Algorithm • 2-Frame Particle Tracking • Velocity is based on individual particle displacements in the time between laser pulses

  4. 3D Imaging • 3-Aperture Camera • Measurement Volume defined by overlap of 3 viewing angles • Combined information from the 3 apertures yields a particle ‘triplet’ for each particle in the common viewing area. Measurement Volume

  5. Principle of ‘Triplets’ 2 eyes Focal Plane 3 apertures ‘Triplet’ Focal Plane

  6. 3D Camera Calibration • Automated Multi-plane Calibration • Capture calibration target images in z-planes parallel to the camera. • Find the target center in each plane to correct misalignment error • Find dewarping polynomials in each plane to correct lens distortion • Find pixel adjustment factor in each plane to correct pinhole deviation. Triplet size at each calibration plane

  7. Validation Part I: Camera Calibration Real Camera Multi-plane Dewarping Mechanical misalignment error Optical aberration and distortion Deviation from pinhole optics (e.g. lens, pixels, aperture locations) Adjusting reference distance and pixel size Perfect Camera • Camera Calibration is used to correct the discrepancy between a real camera and a perfect camera.

  8. Validation Part II: 3D Position Measurement • Grid points on reconstructed calibration targets in multiple z planes

  9. V3V Data Processing Right A Right B Right B Right A Top B Top A Top B Top A Left A Left B Left B Left A TIFF Image 2D Particle Processor Identify particles in images P2D File Triplet Processor Find particles in 3D space P3D File Frame A Frame B Velocity Processor Track particles in 3D space PV3D/GV3D File 3D Velocity Field

  10. 2D Particle Identification Algorithm • 2D Gaussian fit of particle image intensity distribution • Using the Levenberg-Marquardt algorithm for non-linear optimization

  11. Triplet Search Algorithm • A particle in the top image defines a ray in the left and right images • Algorithm searches along these rays for potential matches • Coarse Search (within 1 pixel) • Fine Search (0.5 pixels) From: Sharp et al. (2009) Exp in Fluids, in Press. Calibration planes Coarse search planes Fine search planes

  12. 3D Particle Tracking • 3D particle cloud at t • 3D particle cloud at t + Δt • Relaxation Method for Particle Tracking • See for example: Ohmi, Li (2000) Meas. Sci. Tech. • Particles divided into clusters (similar to interrogation region in PIV) • Probability-based matching From: Sharp et al. (2009) Exp in Fluids, in Press.

  13. Velocity on Rectangular Grid • Randomly Spaced Vector Field to Rectangular Grid • Gaussian-weighted Interpolation (Slice)

  14. Example Experimental Setup Cylinder 3D Camera Mirror Laser

  15. Data Flow over a Cube From: Pan et al. (2007) V3V: A New Tool for 3D Flow Measurement, APS 2007

  16. Data Vorticity Isosurfaces colored by Streamwise Velocity Bluegill Fish Wake Courtesy: George Lauder, Harvard University

  17. Data Vortex Ring from Inclined Exit Re = 2500 From: Troolin, Longmire (2009) Volumetric Velocity Measurements of Vortex Rings from Inclined Exits Exp in Fluids, In Press.

  18. Propeller Measurements Tip velocity = 3.2 m/s Courtesy of INSEAN, Italy

  19. Mixer with Rushton Turbine Courtesy of Penn State U

  20. Wake flow behind a sphere

  21. Measurement of Vortex Ring Impinging on a Plate 1” injector

  22. Vortex Ring Impinging on a Plate

  23. Vortex Ring Impinging on a Plate

  24. Vortex Ring Impinging on a Plate

  25. Vortex Ring Impinging on a Plate

More Related