Continuum Surelite EX 10, Operation And Maintenance Manual

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Appendix A: PIV Operation and Maintenance
PIV description
Particle Image Velocimetry
Particle Image Velocimetry (PIV) is a powerful method of monitoring complex velocity
distributions in diverse media. Typical applications include shear and laminar flows, exhaust
plumes, and airflow around vehicles and aircraft.
The PIV process compares two images, separated in time, taken of light-scattering particles
injected into the flow medium. A Q-switched, pulsed Nd:YAG laser beam, shaped by
cylindrical optics, produces a sheet of light which illuminates a cross-section of the flow
medium. Photographic film or a CCD camera is used to capture two consecutive images (a “
double exposure” ) of the scatter passing through this cross section. A wealth of information
on the scattering particles’ velocities can be re-corded. The recorded data is deconvoluted
using several correlation integrals, achieving a complete two dimension velocity vector field
for large flow areas.
PIV overview
PIV systems
To meet the needs of PIV users and systems manufacturers, Continuum’s PIV systems are
designed for stability, beam quality, and variable pulse separation. The PIV series has two
main configurations:
•
Surelite I PIV
•
Surelite II PIV
Continuum mounts two Surelite lasers on a stable and compact laser bench. Optics on the
same bench combine a pulse from each laser to pass through a single, temperature stabilized
KDP frequency doubling crystal. The result is two 532 nm pulses with nearly identical energy,
beam uniformity and polarization. Dichroic separation is also included. Separation times
between the pulses may vary over a wide range, from 40 ns up to 100 ms. Long-term
performance data shows that PIV lasers maintain constant energy and excellent beam
pointing stability throughout the day.
Continuum also provides PIV systems which combine two separate Q-switched, pulsed
Nd:YAG laser beams on another optical bench. This Beam Access Platform (BAP) uses the
same PIV beam combination optics and temperature stabilized doubling crystal. A BAP
system can achieve specifications similar to the PIV series. Lasers in these systems easily
convert to other applications. Instead of using a single optical bench, these PIV systems give
added flexibility and can provide higher energy, faster repetition rates and seeded pulses.