57:020 Fluid Mechanics
30
Particle Image
Velocimetry (PIV)
• Definition
: PIV measures whole velocity fields by taking two images
shortly after each other and
calculating the distance individual particles travelled within this time. From
the known time difference
and the measured displacement the velocity is calculated.
•Seeding: The
flow medium must be seeded with particles.
• Double Pulsed
Laser: Two laser pulses illuminate
these particles with short time difference.
• Light Sheet
Optics: Laser light is formed into a
thin light plane guided into the flow medium.
• CCD Camera: A fast frame-transfer CCD captures two frames exposed by
laser pulses.
•Timing Controller: Highly accurate electronics control the laser and camera(s).
• Software: Particle image capture, evaluation and display.
PIV
image pair
Cross-correlated
vector field
