Particle Image Velocimetry

Particle Image Velocimetry is a non-intrusive laser optical technique used for determination of the velocity distribution in fluids. The complexity of a system can strongly vary depending on the type of application, however the basic principle of PIV stays the same.
For the purpose of PIV, the fluid is seeded with light scattering particles, which are believed to follow the flow dynamics. The flow is illuminated by a concentrated light source, normally a laser, where as a special camera is acquiring the reflected light from tiny particles in the flow. The camera takes two consecutive images which are synchronized with the two light pulses. The light pulse is very short such that single particles can be identified in the images without blurring effects. The cross correlation software then calculates the displacement of the particles between the first and second image. Since the time between the two light pulses is known, the velocity field can be calculated.