Stereoscopic PIV using optical flow: application to a cavity recirculation
Résumé
Open cavity flows are a class of wall-boundedflows marked by a recirculation vortex, large velocitygradients, and internal three-dimensional (3D) features.That complex structure results in the combination of anupper shear layer, which can develop a KelvinHelmholtzlikeinstability interacting with walls, the flow injectioninside the cavity, the recirculation vortex development,and, for some geometries and Reynolds numbers, a centrifugalTaylorGo¨ rtler-like instability. In order to explorethis flow, experimental measurements of the three componentsof velocity are addressed with stereoscopic twodimensionalparticle image velocimetry (3C-2D PIV) usingan optical flow algorithm. This technique is a valuablediagnostic tool for quantitative instantaneous description of3D flows, as those dominated by vortex motion. PIVcamera calibration is based on a pinhole model using asingle target and camera focal length. The challenging issue is that the studied flow is wall-bounded and subject tolaser reflections, which can alter the quality of particleimages. A treatment of recorded frames is addressed to getthe correct velocity field. PIV measurements are carried outin two orthogonal planes to catch the flow structure andvortex dynamics. Time development of TaylorGo¨rtlerlikevortices is also confronted to the results obtained inprevious studies.