Generation and control of tracer particles for optical flow investigations in air

Abstract

The production of monodisperse tracer particles with suitable properties for optical flow investigations, such as small size, spherical shape, smooth surface, appropriate density and diffraction index, non-evaporating and agglomerating, electrically neutral, non-toxic and easily removable, is a challenging task. It is shown that high concentrations of narrow band particle size distributions, with a mean diameter below 1 µm, can easily be generated by means of multi-hole nozzles under overcritical pressure conditions. In particular, it is shown that existing explanations of the importance of certain design features of the Laskin nozzle are of minor importance for the generation of appropriate tracer tracer particles.