The simulation of cavitating flows is a challenging problem both in terms of modelling the physics and developing robust numerical methodologies. Such flows are characterized by important variations of the local Mach number and involve thermodynamic phase transition. To simulate these flows by applying homogeneous models, an appropriate equation of state (EOS) is necessary to cover all possible fluid states (pure liquid, two-phase mixture and pure vapour). Moreover, the numerical method has to handle any Mach number accurately. This paper presents a one-fluid compressible Reynolds-Averaged Navier-Stokes (RANS) solver with a preconditioning scheme. The cavitation phenomenon is modelled by two different liquid-vapour mixture EOS. The mathematical and thermodynamic properties are studied. Steady and unsteady numerical results are given for a Venturi geometry and comparisons are made with experimental data.

Correlated experimental and numerical studies were carried out to analyse cavitating flows and to describe the twophase flow structures of attached sheet cavitation in Venturi geometries. New double optical probe measurements were performed and special data processing methods were developed to estimate void ratio and velocity fields for cold water flows. By applying a computational method previously developed in LEGI Laboratory based on the code Fine TM /Turbo and on a barotropic approach, several steady calculations were performed in cold water cavitating flows. Local and global analyses were proposed based on comparisons between experimental and numerical results.

International audienceIn a recent study, an original formulation for the mass transfer between phases has been proposed to study one-dimensional inviscid cavitating tube problems. This mass transfer term appears explicitly as a source term of a void ratio transport-equation model in the framework of the homogenous mixture approach. Based on this generic form, a two-dimensional preconditioned Navier-Stokes one-fluid solver is developed to perform realistic cavitating flows. Numerical results are given for various inviscid cases (underwater explosion, bubble collapse) and unsteady sheet cavitation developing along Venturi geometries at high Reynolds number. Comparisons with experimental data (concerning void ratio and velocity profiles, pressure fluctuations) and with a 3-equation model are presented

International audienceA compressible, multiphase, one-fluid inviscid solver has been developed to investigate the behaviour of various cavitation models. A new source term for the mass transfer between phases is proposed. A range of models from three to five equations is compared. Numerical simulations are performed on rarefaction problems and compared with reference solutions

The development of an improved new IBM method is proposed in the present article. This method roots in efficient proposals developed for the simulation of

A fully three-dimensional linear stability analysis is carried out to investigate the unstable bifurcations of a compressible viscous fluid past a sphere. A time-stepper technique is used to compute both equilibrium states and leading eigenmodes. In agreement with previous studies, the numerical results reveal a regular bifurcation under the action of a steady mode and a supercritical Hopf bifurcation that causes the onset of unsteadiness but also illustrate the limitations of previous linear approaches, based on parallel and axisymmetric base flow assumptions, or weakly nonlinear theories. The evolution of the unstable bifurcations is investigated up to low-supersonic speeds. For increasing Mach numbers, the thresholds move towards higher Reynolds numbers. The unsteady fluctuations are weakened and an axisymmetrization of the base flow occurs. For a sufficiently high Reynolds number, the regular bifurcation disappears and the flow directly passes from an unsteady planar-symmetric solution to a stationary axisymmetric stable one when the Mach number is increased. A stability map is drawn by tracking the bifurcation boundaries for different Reynolds and Mach numbers. When supersonic conditions are reached, the flow becomes globally stable and switches to a noise-amplifier system. A continuous Gaussian white noise forcing is applied in front of the shock to examine the convective nature of the flow. A Fourier analysis and a dynamic mode decomposition show a modal response that recalls that of the incompressible unsteady cases. Although transition in the wake does not occur for the chosen Reynolds number and forcing amplitude, this suggests a link between subsonic and supersonic dynamics.

The simulation of cavitating flows is a challenging problem both in terms of modelling the physics and developing robust numerical methodologies. Such flows are characterized by important variations of the local Mach number, compressibility effects on turbulence and involve thermodynamic phase transition. To simulate these flows by applying homogeneous models and Reynolds averaged codes, the turbulence modelling plays a major role in the capture of unsteady behaviours. This paper presents a one-fluid compressible Reynolds-Averaged Navier-Stokes (RANS) solver with a simple equation of state (EOS) for the mixture. A special focus is devoted to the turbulence model influence. Unsteady numerical results are given for Venturi geometries and comparisons are made with experimental data.

International audienceA compressible, two-phase, one-fluid solver has been developed to investigate the behaviour of cavitation models including thermodynamic effects. The code is composed by three conservation laws for mixture variables (mass, momentum and total energy) and a supplementary transport equation for the void ratio. Two formulations for the mass transfer between phases are studied. Numerical simulations are firstly performed on rarefaction cavitating problems in which the working fluid is hot water and freon R-114. A realistic turbulent Venturi case with freon R-114 is performed and comparisons are done between 3- and 4-equation models. A warming effect is highlighted downstream the cavitation pocket in the region of pressure recuperation