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

TLDR

The study aimed to evaluate how different turbulence models affect unsteady cavitation in a Venturi by comparing numerical results to experimental data. Two‑dimensional viscous, compressible, turbulent cavitation was simulated in a Venturi using an implicit finite‑volume SIMPLE solver for RANS equations with a barotropic vapor/liquid state law, implementing four turbulence models (standard k‑ε RNG, modified k‑ε RNG, k‑ω, and k‑ω with compressibility). Standard k‑ε RNG and k‑ω models without compressibility failed to capture cavitation self‑oscillation, while the modified k‑ε and compressible k‑ω models matched experimental void ratios, velocity fields, and unsteady behavior, underscoring the critical role of compressibility.

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.