Particle Image Velocimetry (PIV) is a method used to measure velocities and related properties in fluids using, usually seeded, particles.
History
Technique
In order to measure the velocity at least two exposures are needed. They can be recorded on one or several frames.
The frames are split in a large number of interrogation areas . It is then possible to calculate a vector for each zone with help of statistics (auto-correlation /cross-correlation).
Advantages
The method is to a large degree nonintrusive, the added tracers do in general not cause a
distortion of the fluid.
Another advantage is that the method is capable of measuring the entire field.
Drawbacks
The particles will, due to their higher density, not follow the motion of the fluid as smooth as the rest of the gas/liquid.
The methode will in general not be able to mease components along the z-axis (towards to/away from the camera). These components might not only be missed, they might also introduce an interference in the data for the x/y-components.
Applications
Various applications where fluid flow charateristics are to be studied on a microscopic scale. For example, vortex formation through prosthetic heart valves.
See Also
Sources
Particle Image Velocimetry, Raffel M., Willert C. and Kompenhans J. 1998. Heidelberg: Springer-Verlag.