Experimental and numerical investigation of two physical mechanisms influencing the cloud cavitation shedding dynamics

Petar Tomov (1) , Kilian Croci (1) , Sofiane Khelladi (1) , Florent Ravelet (1) , Amélie Danlos (2) , Farid Bakir (1) , Christophe Sarraf (1)

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

The paper presents numerical and experimental investigations of the existence of two different physical mechanisms as principal origin of cloud cavitation shedding. The two mechanisms are the re-entrant jet formed at the cavity closure region and the shock wave propagation due to the condensation of vapor structures. The experimental observations of these phenomena are done at a fixed Reynolds number of about 1.2 × 10 5 by means of a high-speed camera on a transparent horizontal Venturi nozzle with 18° /8° convergent/divergent angles, respectively. A wavelet analysis is applied with several cavitation numbers in order to associate some image series to the occurrence frequencies of the two shedding mechanisms. In complement, a numerical model is performed in order to access to a 3D representation of the different phenomena. The compressible Navier-Stokes equations coupled with the Homogeneous Equilibrium Mixture Model are solved with a Finite Volume solver based on Moving Least Squares approximations. A snapshot Proper Orthogonal Decomposition technique is applied on both numerical and experimental results. The energy levels of different modes from numerical and experimental data are found to be in a good agreement. Instantaneous pressure peaks of the order of 10 bar, associated with erosive condensation shock wave, are numerically identified. The 3D numerical simulations reveal also that side-entrant jet flow is partially responsible for the re-entrant jet influence on the cloud cavitation shedding.

Mots clés: Cavitation Shedding; Re-entrant Jet; Condensation Shock Wave; Numerical Simulations; HEM; POD; Wavelet; Venturi

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

Petar Tomov, Kilian Croci, Sofiane Khelladi, Florent Ravelet, Amélie Danlos, et al.. Experimental and numerical investigation of two physical mechanisms influencing the cloud cavitation shedding dynamics. 2016. ⟨hal-01284006⟩