Particle Image Velocimetry

Particle Image Velocimetry (PIV) belongs to the class of optical “whole- field” measuring techniques. The name of the method is self-explaining: The velocity distribution in a whole field of a fluid flow is determined by measuring the displacements Δs that the images of tracer particles experience during a time interval Δt. Local, instantaneous velocity values (and directions) w(x,y) = Δs / Δt are measured simultaneously at many positions (x, y) in the field of view. The idea of determining flow velocities by measuring the displacement of tracer particles is not quite new and was in practical use long before the name Particle Image Velocimetry appeared. The new name arose from the possibility of registering the particle images in digital form and efficiently handling the large amount of planar, quantitative data with the techniques of digital image processing. The state of the art for the period prior to the PIV era is well documented in the article by Emrich [414].