Particle Tracking Velocimetry (PTV)

Particle Tracking Velocimetry (PTV) is one of the oldest measuring techniques in fluid mechanics. It is often called low particle number density Particle Image Velocimetry (PIV) (Adrian, 1991). The two methods have indeed in common that they determine the velocity from the displacement of particles in a moving fluid during a prescribed time interval. In contrast to PIV, in which the mean displacement of a small group of particles is sought for, PTV tracks the trajectories of individual particles in three-dimensional space. Particle identification and determination of its position in space is a very important step in PTV. This is only possible if the number density, i.e. the number of particles per unit volume, ρ N = N / V, where N is the number of particles in an observation volume V, is not too high.