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.