partikelbildvelocimetri

Partikelbildvelocimetrie, commonly abbreviated as PIV, is an optical technique used to measure velocity fields in fluids by tracking seeded tracer particles illuminated by light and recorded by cameras. It provides a full-field, non-contact view of flow motion, in contrast to point measurements from instrumentation such as probes.

The basic principle involves seeding the fluid with small, neutrally buoyant particles and illuminating a plane of the flow with a pulsed light source, typically a laser sheet. Two images are captured in quick succession, separated by a known time interval. The images are subdivided into interrogation windows, and a cross-correlation algorithm is applied to corresponding regions to estimate the average particle displacement between frames. The velocity field is obtained by dividing the measured displacement by the time interval. Variants include two-dimensional PIV for planar flows, stereo-PIV for obtaining all three velocity components in a plane, and tomographic PIV for reconstructing three-dimensional velocity fields within a volume.

Setup and workflow typically include: appropriate particle seeding and matching particle size to flow dynamics; optical access and alignment of the laser and cameras; calibration to map image space to physical space; image acquisition with synchronized cameras; multi-pass cross-correlation with decreasing window sizes; post-processing for outlier detection and smoothing; and validation against known benchmarks or simulations.

Common extensions cover time-resolved PIV for high temporal resolution, micro-PIV for microfluidic applications, and holographic or tomographic variants for volumetric measurements. PIV is widely used in aerodynamics, hydrodynamics, combustion, and biomedical engineering to quantify complex, turbulent flows.