Sample image from a high-speed PIV experiment (massive separation over a rounded ramp, S19Ch wind-tunnel, [1-2]).
Associated sequence of vorticity snapshots, illustrating the formation of turbulent eddies during separation.
Particle Image Velocimetry is one of the most frequently used experimental techniques in fluid mechanics. Its direct aim is to determine by a non invasive way the instantaneous velocity field in a flow zone. As material has become more and more robust and performing, PIV is now an accessible tool to extract precious flow information such average flow fields, spatial correlations, or tracking of coherent structures for instance.
According to the optics and geometrical arrangement chosen, the displacement may be determined either in a plane (2D), or in a volume (3D), and, in the case of a planar measurement, only the in-plane displacement components (2C) or the entire displacement (3C) may be measured. By increasing order of complexity, this leads to the following configurations, all of which are routinely used or being developed at ONERA:
Currently, the MTRO team of DAFE possesses several commercial acquisition systems, listed in the Equipment page. Processing of the recorded particle images is then performed with the in-house GPU-based software FOLKI-SPIV, which enables to compute a dense, over-sampled stereo vector field (one vector per image pixel) in about 0.5 s (result obtained for 4 Mpixel images processed on an NVIDIA Tesla C2050 GPU). FOLKI-SPIV is the first software developed by the ALPIV team, which gathers researchers and PhD students from both DTIM (Information Processing and Modelling Department) and DAFE.
[1] Gardarin B., Jacquin L., Geffroy P., Flow separation control with vortex generators, AIAA 2008-3773, 4th AIAA Flow control conference, Seattle, WA, USA, 2008.
[2] Losfeld G., Réception d'un système de vélocimétrie par images de particules résolu en temps, ONERA RT 1/14297 DAFE, 2009.
