TomoPIV

TomoPIV, short for tomographic particle image velocimetry, is a velocity measurement technique that captures three-dimensional, three-component (3D-3C) flow fields within a volume. It extends conventional PIV by reconstructing a volumetric distribution of tracer particles from multiple perspective views and then determining motion between successive volumes.

In practice, the flow is seeded with tracer particles and illuminated by a pulsed light source. Synchronized cameras positioned at different angles record images of the illuminated volume. A calibration procedure maps image coordinates to a common three-dimensional space. The captured views are used to reconstruct the 3D particle distribution within interrogation volumes by tomographic techniques, commonly MART or SMART-based algorithms. Once the particle field is reconstructed for consecutive time steps, 3D cross-correlation or 3D particle tracking is performed to yield the instantaneous 3D velocity field, typically represented on a regular grid. Derived quantities such as vorticity and strain rate can be computed from the velocity field.

Requirements for TomoPIV include ample optical access for multiple views, appropriate seeding density, a pulsed laser or equivalent illumination, and a robust calibration procedure. The technique is sensitive to calibration accuracy, particle image density, and optical aberrations; reconstruction quality can be affected by occlusions and particle overlap in densely seeded flows. TomoPIV is widely used in aerospace, automotive, environmental, and industrial flows, as well as in fundamental fluid mechanics research, for capturing complex, unsteady 3D flow structures that are difficult to measure with traditional planar methods. Variants and ongoing developments continue to improve reconstruction algorithms, processing speed, and applicability to challenging flow regimes.