High Quality Content by WIKIPEDIA articles! Particle image velocimetry (PIV) is an optical method of fluid visualization. It is used to obtain instantaneous velocity measurements and related properties in fluids. The fluid is seeded with tracer particles which, for the purposes of PIV, are generally assumed to faithfully follow the flow dynamics. It is the motion of these seeding particles that is used to calculate velocity information of the flow being studied. Other techniques used to measure flows are Laser Doppler velocimetry and Hot-wire anemometry. The main difference between PIV and those techniques is that PIV produces two dimensional vector fields, while the other techniques measure the velocity at a point.