Stereoscopic PIV using optical flow: application to a cavity recirculation
Résumé
Open cavity flows are a class of wall-bounded
flows marked by a recirculation vortex, large velocity
gradients, and internal three-dimensional (3D) features.
That complex structure results in the combination of an
upper shear layer, which can develop a KelvinHelmholtzlike
instability interacting with walls, the flow injection
inside the cavity, the recirculation vortex development,
and, for some geometries and Reynolds numbers, a centrifugal
TaylorGo¨ rtler-like instability. In order to explore
this flow, experimental measurements of the three components
of velocity are addressed with stereoscopic twodimensional
particle image velocimetry (3C-2D PIV) using
an optical flow algorithm. This technique is a valuable
diagnostic tool for quantitative instantaneous description of
3D flows, as those dominated by vortex motion. PIV
camera calibration is based on a pinhole model using a
single target and camera focal length. The challenging issue is that the studied flow is wall-bounded and subject to
laser reflections, which can alter the quality of particle
images. A treatment of recorded frames is addressed to get
the correct velocity field. PIV measurements are carried out
in two orthogonal planes to catch the flow structure and
vortex dynamics. Time development of TaylorGo¨rtlerlike
vortices is also confronted to the results obtained in
previous studies.