Post on 02-Jun-2018
transcript
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Imaging Techniques for Flow and Motion Measurement
Lecture 3
Lichuan Gui
University of Mississippi
2011
Particle Image Velocimetry (PIV)
Introduction
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Particle Image Velocimetry (PIV)
Optical, non- or minimally-intrusive, fluid flow measurement
technique;
Instantaneous flow measurements in two-dimensional (2D) area
or three-dimensional (3D) volume field of views;
Basic procedure of PIV Flow visualization
Flow field seeded with small tracer particles
Particles usually illuminated by a laser light sheet
Image recording
Particle images captured by an imaging system
Image evaluation
Usually using auto- or cross-correlation algorithm
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Stroboscopic illumination techniques
Flow visualization with small particles
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Oil drop in laminar pipe flow (Air) Solid particles in water flow
Multiple exposed particle images
Flow visualization with small particles
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2D & 2-component PIV Systems
CW laser with high-speed photo or video camera
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Fluorescent particles in a microdevice
0.540.41 mm2, 30 fps
Smoke flow in air
0.50.5 mm2, 500 fps
Consecutive singly exposed PIV recordings
2D & 2-component PIV Systems
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Measurement
volume
Lens
t=t
0
t=t0+t
Lens system
& Camera
Light
sheet
Single exposed recording Double exposed recording
Fluid flow seeded with
small tracer particles
Image #1
t=t0+t
Image #2
Exposure #1
Exposure #2
Laser
Standard 2D PIV
2D & 2-component PIV Systems
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Image plane
Objective
Lens
Laser light sheet
Laser light sheet
Image plane
Objective Lens
S
S
L
L
Scale factor: M=L/L
Time interval: t
Velocity: V=S/t=MS/ t
Velocity determination with standard 2D PIV
2D & 2-component PIV Systems
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Flood Illumination
l=532 nm
l= 610 nm
Nd:YAG LASER
MICROSCOPE
BEAM EXPANDER
CCD CAMERA
MCROFLUIDIC DEVICE
Nd:YAG Laser
Micro Device
Flow in Flow out
Glass
cover
CCD Camera
(1280x1024 pixels)
Beam
Expander
Epi-fluorescent
Prism / Filter Cube
Microscope
Focal Plane
Micro-PIV image pair
Micro-Fluidics Lab
Purdue University
Micro-scale PIV (MPIV) System
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Stereo PIV 3 velocity components in a plane
Two cameras
Holographic PIV
3 velocity components in a 3 dimensional volume
Complex and precise illumination
Defocusing PIV (Pereira et al. 2000)
Allow images to become defocused
Single camera/ color CCD, particle image tracking
Multiple-sheet PIV (Raffel et al.,1995 )
Multiple laser light sheet, single camera
3D scanning PIV (Brcker, 1997)
Scanning a 3D volume with a laser beam
Single high speed camera
3D or 3-component PIV Systems
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Stereo PIV configurationsa. Translation systems
(lateral displacement)
b. Rotational systems
(angular displacement)
Scheimpflug condition
3D or 3-component PIV Systems
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Stereo PIV data reduction
- Translation systems (Mn=di/do)
3D or 3-component PIV Systems
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Stereo PIV data reduction
- Rotational system (Mnconstant)
3D or 3-component PIV Systems
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Holographic PIV (HPIV) System
Holographic diagnostics of a 3D particle filed
a. Hologram recording
b. Hologram reconstruction
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Holographic PIV (HPIV) System
Holographic recording of particles
Interference pattern in a HPIV recording
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Holographic PIV (HPIV) System
Reconstructed HPIV particle images
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Holographic PIV (HPIV) System
Example of HPIV system (recording)
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Holographic PIV (HPIV) System
Example of HPIV system (reconstruction)
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Practice with EDPIV software
1. Read EDPIV help manual page to know details in Raw Image Format window
2. Open images in application example #0 with EDPIV and look at image details.
EDPIV software and sample images are available at http://www.edpiv.com/
Homework