PIV & VISUALISATION
Litron is the acknowledged leader in supplying lasers for PIV applications, ranging from lamp pumped Nd:YAG lasers in the 15Hz to 200Hz repetition rates range up to diode pumped Nd:YLF and Nd:YAG lasers giving kilohertz repetition rates for high speed applications.
LITRON LASERS FOR PIV & VISUALISATION
Particle image velocimetry (PIV) is a widespread technique for analysing fluid flows in gases and liquids. Typical application areas are in aerodynamics, hydrodynamics, combustion analysis and medical imaging, with flow velocities varying from centimetres per second to hypersonic.
Pairs of laser pulses, typically from a dual cavity Nd:YAG or Nd:YLF laser are formed into a sheet using light sheet forming optics to illuminate the area of interest. Particles within the flow field scatter light back to form an image on a camera and a computer with specialised PIV software analyses the images to create a two-dimensional flow field showing speed and direction at various points. Holographic or tomographic PIV techniques enable a three-dimensional image to be obtained.
Advances in camera design have enabled high speed PIV to become a reality for looking at very high velocity flow phenomena at frame rates of several kilohertz, requiring the use of high-speed lasers operating at up to 20kHz.
For two-dimensional PIV, laser beam quality is an important consideration. Good spatial uniformity gives images that are clear and free from under or over exposed regions. Lasers with low divergence beams with corresponding low M2 values, even TEM00 can give thinner light sheets that extend over a larger image area than other lasers with higher divergence.