Particle Image Velocimetry

This tutorial presents the underlying theory of Particle Image Velocimetry (PIV), with an emphasis on the practical consequences of the modelling assumptions made at each step of a modern Digital PIV (DPIV) workflow. The session touches on approaches spanning two-component - two-dimensional (2C–2D) velocity-field measurements through to three-component - three-dimensional (3C–3D) techniques. Particular attention is given to how velocity-gradient (VGT) effects and peak bias are coupled to the effective spatial resolution of the imaging system and to the chosen interrogation region/volume size.A recurring theme will be the connection between the physical measurement problem (tracer response, seeding, illumination, and imaging) and the statistical signal-processing problem (interrogation region/volume definition, cross-correlation structure, peak detection and bias, filtering choices, and uncertainty quantification). Using representative examples, the tutorial highlights common failure modes and “rules-of-thumb” to help design experiments and analysis settings that are defensible, repeatable, and fit-for-purpose.The tutorial closes by linking implementation choices to typical research use-cases, with particular attention to wall-bounded turbulent shear flows, and to flow physics can place additional constraints on the measurement chain.