PIV is a non-intrusive, quantitative method to measure instantaneous velocity fields in fluid. The measurement system can be used to determine velocity fields and wake fields around ships, underwater vehicles, propellers and marine risers. The 3D PIV system consists a Nd:YAG pulse laser, two CCD cameras, and a computer for operations of system calibration, image acquisition, and data analysis.

For use of PIV technique, the fluid should be evenly seeded with tiny, neutrally buoyant particles following the flow. A pulsed laser light sheet is used to illuminate the flow field twice within a short time interval. The positions of the particles are recorded on digital CCD cameras at each instant while the light sheet is pulsed. Tracer particle images in the flow are used as raw data for the PIV analysis, and the direction and displacement of the particle movements are directly related to the flow velocity.

PIV technique is a very useful tool in the hydrodynamics research field. The unique feature of the technology is instantaneous, simultaneous field and non-intrusive measurement. This allows a researcher to obtain instantaneous flow structure, especially suitable to unsteady flow investigation and having less disturbance to the measurement fluid, therefore, it increases the accuracy of results compared to intrusive measurement methods. The PIV system has been updated and applied in several different experiments since purchased from LaVision Inc. in 2003.

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