Particle image velocimetry (PIV) is an optical method of flow visualization used in education and research.
Particle tracking velocimetry (PTV) is a velocimetry method, i.e. a technique to measure velocity of particles.
So then, 50 odd years on is this not about the same pedagogical device as PCB's SOP only techno-ed up a bit?
Has PIV been applied to barge, sharpie, advanced sharpie, &etc hydraulic flow lines yet? To chines and fore foots? (To models, I suppose.)