Three-dimensional stationary flow over a backward-facing step
Résumé
Three-dimensional stationary structure of the flow over a backward-facing step is studied experimentally. Visualizations and Particle Image Velocimetry (PIV) measurements are investigated. It is shown that the recirculation length is periodically modulated in the spanwise direction with a well-defined wavelength. Visualizations also reveal the presence of longitudinal vortices. In order to understand the origin of this instability, a generalized Rayleigh discriminant is computed from a two-dimensional numerical simulation of the basic flow in the same geometry. This study reveals that actually three regions of the two-dimensional flow are potentially unstable through the centrifugal instability. However both the experiment and the computation of a local Görtler number suggest that only one of these regions is unstable. It is localized in the vicinity of the reattached flow and outside the recirculation bubble.
Origine : Fichiers produits par l'(les) auteur(s)
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