Particle Image Velocimetry (PIV) is a technique to visualise flow and measure instantaneous flow velocity and direction of a fluid. The technique relies on two images being taken from picoseconds to milliseconds apart, allowing computer analysis to follow the movement of individual particles in two dimensions. The fluid must have visible particles small enough to faithfully follow the flow of the liquid or gas sample. These particles can be part of the sample, or seeded into the liquid or gas to aid the visualisation and analysis. PIV is commonly used in many different areas, such as combustion, aerosol analysis, pipe flows and wind tunnel experiments.
Laser light is used due to the high intensity beams that can be produced and the ability of the beam to be shaped into a 2 dimensional light sheet that forms the canvass of the image. The power requirement is proportional to the size of the sample that needs to be measured with a large sample requiring higher powers. The beam pointing stability is also crucial as any movement in the light sheet, will artificially corrupt the velocity measurements. A range of laser wavelengths can be used depending on sensitivity of the measurement camera.
A range of Laser Quantum lasers are suitable for PIV , but listed below are a series of lasers across a range of powers.