Particle image velocimetry - an advanced experimental tool for the investigation of turbulent flow fields

For the characterization of turbulent flows it is often required to measure both, the temporal behavior of the velocity fluctuations along with their spectral contents and the spatial flow structure. Conventional point-wise measurement techniques such as hot-wire or laser Doppler velocimetry have been applied for a long time in order to obtain the temporal information at a single point. Since a few years the Particle Image Velocimetry (PIV) technique, which for the first time allows to measure instantaneous velocity vector maps, enables quantitative insight into the development of the spatial structures as well. It will be shown that by employing more complex multi-laser, multi-camera set-ups for PIV, it becomes possible to measure other relevant quantities required for the understanding of turbulent flows such as the complete velocity gradient tensor or the components of the spatio-temporal correlation tensor for example