Tomographic PIV

Tomographic-PIV is a volumetric three-component velocimetry technique. Full velocity and velocity gradient tensor fields can be obtained from the Tomographic-PIV method, which can provide comprehensive information on complicated three-dimensional flows like turbulent boundary, including the nature and distribution of coherent vortex structures. Microvec offers 4 different  Tomographic-PIV algorithms including patented Intensity Enhanced MART.

Figure 1. Microvec TOMO-PIV example showing Spiral vortex breakdown on delta wing

Tomography is a word originally from medical science meaning imaging by sections or sectioning through the measurement volume. TOMO PIV reconstructs the images of the particles in the sections of the measurement volume, and then does the volume correlation between two neighbor time steps to get the velocity field. In a sense, TOMO-PIV is the most orthodox 3D PIV technique extended from the traditional 2D PIV. A typical Microvec TOMO-PIV setup is shown below.

MicroVec has implemented a new software module to add TOMO-PIV module to its PIV software lineup.

MicroVec TOMO-PIV software module has following features:

  • Automatic recording images to hard disk or to Buffer Memory
  • Volumetric calibration algorithm
  • Particle images enhancement technique
  • Sliding background elimination
  • Particle density compensation
  • Geometric reconstruction technique
  • Multiplicative Algebraic Reconstruction Techniques (MART)
  • Sparse MART and intensity enhanced MART
  • Spatial Filter MART
  • Convolution MART
  • Volumetric cross-correlation with window deformation algorithm and multi-pass iterations
  • Outlier detection and correction
  • Velocity post-process technique
  • Multi-CPU parallel computing
  • GPU acceleration
  • Results supported by Tecplot

Case 1: Vortex Ring and Swirl

The experiment was conducted in a water channel. 4 cameras were used at 200fps with an 8W DPSS laser in a water tank (see picture above).

Pictures courtesy of Dr. Qi Gao, Beijing University of Aeronautics and Astronautics.