Affiliations: Department of Mechanics and Aeronautics, University of
Roma "La Sapienza," Roma, Italy
Abstract: The effects of different tracer particles used in the PTV technique
on the velocity field are investigated. The measurements are taken in a water
round jet at a Reynolds number equal to about 40000, a flow field widely
examined in the literature, in which strong velocity differences are
encountered. The interest is focused onto particles with different density.
Although the mean and rms values are almost unaffected, both measurements
obtained with light and heavy particles (in comparison to the density of the
fluid) reveal a modified velocity field. The moments of velocity differences
(structure functions) point out that such a modification is felt within each
range of flow scales. Particles with density almost equal to that of the fluid
reproduce the flow behaviour over all the scales.