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Imaging Techniques for Flow and Motion Measurement
Engr 699, Section 81
Instructor: Lichuan Gui
Spring Semester 2011
Tuesdays and Wednesdays 2:00-3:15pm
NCPA class room #1128
Class material available at http://lcgui.net/index_files/Page946.html
EDPIV software available at http://edpiv.com
Imaging Techniques for Flow and Motion Measurement
Lecture 1
Fluid Flow Measurement Methods
Overview
Lichuan Gui
University of Mississippi
2011
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Discussion
• Why do fluid flows need to be measured?
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Discussion
• What variables need to be measured?
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Velocity
Pressure
Temperature
Density
?
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Discussion
• Non-imaging measurement techniques:
– Velocity:
• U-tube manometer
• Pitot probe
• Hot wire/film anemometer (HW/ HF)
• Laser Doppler velocimetry/anemometry (LDV /LDA)
• Sonic anemometer
– Pressure: pressure sensors
– Temperature: temperature sensors
– Density: reduced from P, T etc.
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Non-imaging Techniques
• Velocity measurement using U-tube manometer
V c
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
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 P1  P2  2
- Calibration required to determine coefficient “c”
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Non-imaging Techniques
• Velocity measurement using pitot probes
2-hole pitot probe (1D)
3-hole pitot probe (2D)
5-hole pitot probe (3D)
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Non-imaging Techniques
• Velocity measurement using HW & HF
Hot wire
Hot film
Hot film
Non-imaging Techniques
• Velocity measurement using HW & HF
Energy balance
Electric resistance
Heat convection coefficient
Flow velocity
- Different systems: CCA, CVA, CTA
- Calibration required
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Non-imaging Techniques
• Laser Doppler Velocimetry/Anemometry
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Non-imaging Techniques
• Summary of the velocimetries
– Pitot proble, HW & HF
• Point-by-point measurement
• Intrusive
• Calibration required
– LDV (LDA)
• Point-by-point measurement
• Non-intrudsive
• No calibration
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Imaging Techniques
• Three groups of flow visualization methods
– Foreign material added to the fluid flow
– Optical methods sensitive to refraction index
changes
– Foreign energy (e.g. heat or electric discharge)
added to the fluid flow
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Imaging Techniques
• Visualization of flow direction
– Example: Dye lines in water flow
Vortex flow behind a yawed cylinder visualized
with mixture of ink, milk and alcohole
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Imaging Techniques
• Visualization of flow direction
– Example: Smoke lines in air flow
Smoke lines around an airfoil model in a wind-tunnel
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Imaging Techniques
• Visualization of flow direction
– Example: Tuft Screen
Trailing vortices behind an inclined delta-wing
as visualized by a tuft screen
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Imaging Techniques
• Velocity measurement with tracers
– Example: Hydrogen-bubble technique
Consecutive rows of hydrogen bubbles indicating
Velocity profiles a flat plat boundary layer
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Imaging Techniques
• Velocity measurement with tracers
– Example: Small particles
Stroboscopic illumination of oil drop
in laminar pipe flow
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Imaging Techniques
• Optical methods for compressed flows
– Shadowgraph
Shadowgraph of a sphere flying at M=1.7
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Imaging Techniques
• Optical methods for compressed flows
– Schlieren Method
Schlieren photograph around a sphere flying
at hypersonic speed
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Imaging Techniques
• Other methods
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X-ray & Echo PIV
Molecular Tagging Velocimetry (Seedless velocimetry)
Laser Speckle Photography
Temperature measurement with particle Brownian motion
More
• Summary
– Full-field measurement (2D & 3D)
– Non-intrusive
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