Complete removal of ghost particles in Tomographic-PIV

Abstract

This paper discusses and compares several methods, which aim to remove spurious peaks, i.e. ghost particles, from the volume intensity reconstruction in Tomographic-PIV. The assessment is based on numerical simulations of timeresolved tomographic-PIV experiments in linear shear flows. Within the reconstructed volumes intensity peaks are detected and tracked over time. These peaks are associated to particles (either ghosts or actual particles) and are characterized by their peak intensity, their size and their track length. Peak intensity and track length are found to be effective in discriminating between most ghosts and the actual particles, although not all ghosts can be detected using only a single threshold. The size of the reconstructed particles does not reveal an important difference between ghosts and actual particles. Simultaneous plotting of peak intensity and track length however does, under certain conditions, allow a complete separation of ghosts and actual particles. The ghosts can have either a high intensity or a long track length, but not both combined like all the actual particles. Finally removing the detected ghosts from the reconstructed volume and performing additional MART iterations can decrease the particle position error at low to moderate seeding densities, but increases the position error and tracking errors at higher densities.