Image velocimetry (PIV) measuring instrument

particleCCD

Volumetric Velocimetry (VV) also known as 3D PIV or Tomo PIV provides truly volumetric velocity data, using to four cameras with telecentric lenses, and a thick light sheet or a scanning thick light sheet. Time-resolved VV solutions using time-resolved CMOS cameras, as well as “classical” solutions with CCD cameras are available. For low to medium seeding concentration, Particle Tracking Velocimetry (PTV) is used with two or three cameras, whereas for high seeding concentration (like PIV) a Least Squares Matching (LSM) algorithm provides 3 velocity components in a 3D volume, often described as 3D-3C (3 dimensions - 3 components). Full shear tensor directly from the LSM data processing The LSM is a very computationally efficient and fast processing method, providing much more information than classic cross-correlation based tomographic PIV: the full shear tensor describing scale, rotation and shear without the need to derive this data from the velocity field is inherently available. The computational speed increase is twofold: 1) LSM is faster than cross correlation, and 2) the full shear tensor is computed in the same calculation as the velocity field. With PIV processing, the shear tensor must be computed after the velocity field. Straightforward upgrade path from Stereo PIV to Volumetric Velocimetry Stereo PIV systems are easily upgraded to volumetric Particle Tracking Velocimetry (PTV) by adding telecentric camera lenses and a software add-on. Adding a 3rd camera, tomographic PTV in medium seeded flows is possible, and adding a 4th camera, Volumetric Velocimetry using a Least Squares Matching algorithm is possible.