Evaluation of the Turbulence Model Influence on the Numerical Simulations of Unsteady Cavitation

Abstract

Unsteady cavitation in a Venturi-type section was simulated by two-dimensional computations of viscous, compressible, and turbulent cavitating flows. The numerical model used an implicit finite volume scheme (based on the SIMPLE algorithm) to solve Reynolds-averaged Navier-Stokes equations, associated with a barotropic vapor/liquid state law that strongly links the density variations to the pressure evolution. To simulate turbulence effects on cavitating flows, four different models were implemented (standard k-ε RNG; modified k-ε RNG; k-ω with and without compressibility effects), and numerical results obtained were compared to experimental ones. The standard models k-ε RNG and k-ω without compressibility effects lead to a poor description of the self-oscillation behavior of the cavitating flow. To improve numerical simulations by taking into account the influence of the compressibility of the two-phase medium on turbulence, two other models were implemented in the numerical code: a modified k-ε model and the k-ω model including compressibility effects. Results obtained concerning void ratio, velocity fields, and cavitation unsteady behavior were found in good agreement with experimental ones. The role of the compressibility effects on turbulent two-phase flow modeling was analyzed, and it seemed to be of primary importance in numerical simulations.

Investigation of Cavitation Models for Steady and Unsteady Cavitating Flow Simulation

“…RANS turbulence models have been used to simulate various industrial fluid machines for years because of their good performance in giving acceptable simulation results within a reasonable computational time. For cavitating flow simulations, recent CFD studies showed that these turbulence models would need some modifications in the turbulent eddy viscosity [31,33,34]. There are several different RANS turbulence models for different utilities.…”

“…To improve numerical simulations by taking into account the influence of the local compressibility effect of two-phase mixtures on turbulent closure models, Coutier-Delgosha [33] proposed to reduce the mixture turbulent viscosity of fluid at vapor/liquid interfaces based on the local vapor volume fraction α v by substituting μ T in eq. (3) with μ T_mod :…”

Numerical Simulation of Unsteady Cavitation in a High-speed Water Jet

“…However, in high speed cavitating water jets bubble clouds oscillates intensively and the eddy viscosity in a local area of bubble cloud may be greatly absorbed. In order to capture the unsteadily shedding of bubble clouds a density modification is introduced and then the eddy viscosity is evaluated by the following formula [10,15].…”

Fault Detection and Isolation in Industrial Systems Based on Spectral Analysis Diagnosis

“…During the execution of the strategy of diagnosis, the measurable signals can provide significant information, on the defects appearance to facilitate the determination of the supervision parameters, representing the defects signatures, their degree and persistence. From these parameters, the decisional system can conceive powerful diagnosis approach [1][2][3]. To realise this prospect, we proposes in this work to examine and illustrate the application ability of the spectral analysis approach, in the area of fault detection and isolation industrial systems.…”