Étude expérimentale des écoulements multiphasiques dans une couche limite laminaire décollée.

Abstract : Hydrodynamic cavitation, more specifically attached cavitation, can emerge et develop in complex turbulent flows within laminar boundary layer separations. This phenomenon might be extremely sensitive to the gaz content in the flow. For an easier understanding of the attachment of cavities into laminar separated flows within the influence of air content, we propose to focus our study on viscous silicon oil laminar separated flows, presenting high gas content, within a smooth Venturi geometry. In this study, the inception of several types of attached cavities, filled with air or oil vapor, can be observed into different laminar flow separations. For high pressures, the degassing phenomenon is dominant in the flow, generating attached cavities filled with air presenting interesting dynamics. For low pressures, attach vapor cavities can emerge inducing, if the flow is unstable, the transition to laminar/turbulent transitioning regime in their wake. This transition can also occurs intermittently at higher pressures in the wake of a recirculating air bubble, characteristic to degassing into laminar separated flows. The laminar/turbulent transitioning regime, less sensitive to degassing, is characterized by vortex cavitation, occurring at high frequencies, at the rear of a “short” laminar separation bubble along the divergent Venturi slope. The “short” laminar separation bubble grows until transitioning to a “long” bubble within an large attached cavity. This transition can be associate to thesupercavitation phenomenon.
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Kilian Croci. Étude expérimentale des écoulements multiphasiques dans une couche limite laminaire décollée.. Mécanique des fluides [physics.class-ph]. Ecole nationale supérieure d'arts et métiers - ENSAM, 2018. Français. ⟨NNT : 2018ENAM0052⟩. ⟨tel-02005952⟩

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