INVESTIGATION OF TWO MECHANISMS GOVERNING CLOUD CAVITATION SHEDDING: EXPERIMENTAL STUDY AND NUMERICAL HIGHLIGHT

Kilian Croci (1) , Petar Tomov (1) , Florent Ravelet (1) , Amélie Danlos (2) , Sofiane Khelladi (1) , Jean-Christophe Robinet (1)

1 DynFluid - Laboratoire de Dynamique des Fluides
2 LGP2ES - Laboratoire Génie des Procédés pour l'Environnement, l'Energie et la Santé

Cavitation is a phenomenon of classical interest which can be observed in various applications. It consists in a transition of phase due to a pressure drop under the saturation pressure of a liquid. The unsteady behavior of this phenomenon leads to generate some issues such as erosion, noise or vibrations: as a result the comprehension of the cavity dynamics remains of crucial importance. Unsteady cavitation has been investigated in numerous studies and a mechanism of re-entrant jet has been firstly identified as responsible of the cavity shedding process. Recently, a second shedding mechanism, induced by a shock wave propagation due to the condensation of vapor structures , has been experimentally highlighted with X-ray measurements [1]. The present paper focuses on the experimental detection , with a wavelet method, of these two shedding features on 2D image sequences recorded with a high-speed camera about a double transparent horizontal Venturi nozzle with 18 • /8 • con-vergent/divergent angles respectively. A compressible two-phase flow numerical 3D model is performed in complement in order to illustrate some phenomena hardly perceptible experimentally. NOMENCLATURE ν Kinematic Viscosity of Liquid Water ρ Density of Liquid Water σ Cavitation Number Defined for the Bifurcation σ r Cavitation Number Defined at the Throat f s Frequency of Re-Entrant Jet f w Frequency of Condensing Shock Wave H Throat Height (10 mm) L Non-Dimensional Cavity Closure Length P o Numerical Outlet Pressure P Pressure Measured at X = −6 P r Pressure Estimated at the Venturi Throat P v Saturation Vapor Pressure Re Reynolds Number R Power Spectral Density Ratio St Strouhal Number T Time in Image Sequence T ∞ Numerical Inlet Temperature V in Inlet Flow Velocity V r Flow Velocity at the Venturi Throat W n Wavelet Transform

Domaines: Dynamique des Fluides [physics.flu-dyn]

Kilian Croci, Petar Tomov, Florent Ravelet, Amélie Danlos, Sofiane Khelladi, et al.. INVESTIGATION OF TWO MECHANISMS GOVERNING CLOUD CAVITATION SHEDDING: EXPERIMENTAL STUDY AND NUMERICAL HIGHLIGHT. ASME 2016 International Mechanical Engineering Congress & Exposition IMECE 2016 , Nov 2016, Phoenix, United States. ⟨10.1115/IMECE2016-65420⟩. ⟨hal-01362217⟩