Particle Image Velocimetry (PIV) is a Flow Measurement Technique which can be used to obtain the time dependent full field velocity distributions of single and multi-phase flows. Two dimensional or three dimensional velocity field distributions can be obtained.

Usually, the approach requires seeding the flow with small tracer particles and illuminating with a sheet or volume of light from a pulsed laser. A single or multi-exposure image is recorded of the position  of the particles as a function of time. The spacing between these particle images provides a measure of the local flow velocity. The spacing is determined through imaging techniques.

The advantage of PIV is that it is:
•Non-intrusive into the flow field being studied
•2D or 3D full-field flow measurements can be made
•Instantaneous velocity fields are obtained
•Capability for studying multiphase flows

PIV can be used to study a variety of flow phenomena. Examples of some flow fields which can be studied with PIV include, single and multi-phase channel flows, steam bubble collapse, flow around cylinders in a channel, bubbly pipe flows, free surface experiments, sprays, and heated cavity flows, etc…

The components needed for PIV include: an illumination source, and optical system for illuminating the test section, digital imagers for capturing the flow field, and a system for image processing, particle identification, particle tracking, and vector field cleaning.

The general procedure for PIV image acquisition is, the laser is synchronized with the digital imagers, the laser light is positioned to illuminate the test volume, the scattered light from the tracer particles is recorded with the digital cameras, and then image analysis is performed.