Tests and comparison of different recording set-ups

Particle Image Velocimetry is a technique which, in principle, involves two different steps. In a first step, the images of small tracer particles transported by the flow must be recorded. To obtain such a PIV record, the flow is seeded with tracer particles, the region of interest is illuminated with a sheet of strong laser light and the images of the seeding particles are taken by photographic or video means. In a second step, the PIV record is analyzed by a system generally composed of a reading optics, a computer and an analysis software. The local flow velocity is determined from the displacement of the images of the tracer particles between successive illuminations. The time delay separating these illuminations and the magnification of the recording optics are needed to make the method quantitative.