Imaging Techniques for Flow and Motion Measurement
Lecture 3
Particle Image Velocimetry (PIV)
Introduction
Lichuan Gui
University of Mississippi
2011
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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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Flow visualization with small particles

Stroboscopic illumination techniques
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Flow visualization with small particles

Multiple exposed particle images
Oil drop in laminar pipe flow (Air)
Solid particles in water flow
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2D & 2-component PIV Systems

CW laser with high-speed photo or video camera
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2D & 2-component PIV Systems

Consecutive singly exposed PIV recordings
Fluorescent particles in a microdevice
0.540.41 mm2, 30 fps
Smoke flow in air
0.50.5 mm2, 500 fps
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2D & 2-component PIV Systems

Standard 2D PIV
t=t
Lens
0
Measurement
volume
Laser
Light
sheet
Image #1
t=t
Fluid flow seeded with
small tracer particles
0
Lens system
& Camera
Single exposed recording
Exposure #1
Double exposed recording
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2D & 2-component PIV Systems

Standard 2D PIV
t=t0+t
Lens
Measurement
volume
Laser
Light
sheet
Image #1
t=t
Fluid flow seeded with
small tracer particles
0
Image #2
t=t0+t
Single exposed recording
Lens system
& Camera
Exposure #1
Exposure #2
Double exposed recording
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2D & 2-component PIV Systems

Velocity determination with standard 2D PIV
Image plane
Scale factor:
M=L/L’
Time interval:
t
Laser light sheet
Objective
Lens
Velocity: V=S/t=M·S’/ t
S’
Image plane
Objective Lens
Laser light sheet
L’
L
S
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Micro-scale PIV (MPIV) System
Micro Device
MCROFLUIDIC DEVICE
Flow out
Flow in
CCD CAMERA
Glass
cover
MICROSCOPE
Focal Plane
BEAM EXPANDER
Flood Illumination
Microscope
Beam
Expander
Nd:YAG LASER
Micro-Fluidics Lab
Purdue University
Epi-fluorescent
Prism / Filter Cube
Nd:YAG Laser
Micro-PIV image pair
l=532 nm
l = 610 nm
CCD Camera
(1280x1024 pixels)
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3D or 3-component PIV Systems
– 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 (Brücker, 1997)
• Scanning a 3D volume with a laser beam
• Single high speed camera
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3D or 3-component PIV Systems

Stereo PIV configurations
a. Translation systems
(lateral displacement)
b. Rotational systems
(angular displacement)
Scheimpflug condition
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3D or 3-component PIV Systems

Stereo PIV data reduction
- Translation systems (Mn=di/do)
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3D or 3-component PIV Systems

Stereo PIV data reduction
- Rotational system (Mnconstant)
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Holographic PIV (HPIV) System

Holographic diagnostics of a 3D particle filed
a.
b.
Hologram recording
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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Homework
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/
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