Coloured Tracer Particles Employed for 3-D Particle Tracking Velocimetry (PTV) in Gas Flows

This work describes an improved method for Particle Tracking Velocimetry in three dimensions (3-DPTV), applicable for gaseous flows and based on coloured tracer particles. This method allows a considerable increase of the tracer number density, while maintaining a constant rate of 3-D correspondence ambiguities from the different cameras. It is therefore perfectly suited for gas flows, where a high tracer density is requested to follow small-scale flow features. Furthermore, coloured tracer particles enable a longer next-step searching distance for the lagrangian reconstruction of trajectories. First, theoretical and numerical considerations are presented to check the ability of the employed coloured tracer particles to follow the considered flow. Then, 3-D PTV results obtained by the method described here are shown and appear to be very promising for later investigations of gas flows involving vortical structures and recirculation zones down to small scales, around 1 mm.