Tomographic 3D(t) PIV and recent applications

Abstract

Tomographic Particle Image Velocimetry is a 3D PIV technique based on the illumination, recording, reconstruction and analysis of tracer particle displacements within a three-dimensional measurement volume in a flow. The technique makes use of several simultaneous views of the illuminated particles, typically four, and their three-dimensional reconstruction as a light intensity distribution by means of optical tomography. The reconstruction is performed with the MART algorithm (multiplicative algebraic reconstruction technique), yielding a 3D distribution of light intensity discretized over an array of voxels. The reconstructed tomogram pair is then analyzed by means of 3D cross-correlation with an iterative multigrid volume deformation technique, returning the three-component velocity vector distribution over the measurement volume. The implementation of the tomographic technique in time-resolved mode by means of high-repetition rate PIV hardware has the capability to yield 4D velocity information. As a result the fully (time-dependent) instantaneous velocity gradient tensor is available.