Particle image velocimetry
![Application of PIV in combustion](/Images/godic/202502/01/PIV_through_stagnation_flame1526.jpg")
![PIV-Analysis of a vortex pair. The magnification in the upper left shows the increase in spatial resolution that can be achieved using a modern multi-pass window deformation technique.](/Images/godic/202502/01/PIVlab_multipass1526.jpg")
![PIV analysis of a stalled flat plate, shear rate superimposed](/Images/godic/202502/01/PIV_analysis_of_a_stalled_flat_plate1526.jpg")
Particle image velocimetry (PIV) is an optical method of flow visualization used in education and research. It is used to obtain instantaneous velocity measurements and related properties in fluids. The fluid is seeded with tracer particles which, for sufficiently small particles, are assumed to faithfully follow the flow dynamics (the degree to which the particles faithfully follow the flow is represented by the Stokes number). The fluid with entrained particles is illuminated so that particles are visible. The motion of the seeding particles is used to calculate speed and direction (the velocity field) of the flow being studied.