The presented work aims to identify a Volume of Fluid (VOF) CFD approach for the transient simulation of air/oil flows inside an aero-engine bearing chamber. Typically VOF requires relatively fine grids and consequently small time-steps to sufficiently resolve the formation of oil films and their interaction with air flows. The need to achieve a stationary-state which requires flow times on the order of seconds makes the compromise between simulation accuracy and simulation times a challenging choice when using the VOF method. In this work, the use of the Compressive Interface Reconstruction scheme with bounded second order implicit time discretization has enabled a significant speed-up of the simulation times against the previously adopted explicit Geometric-Reconstruction scheme. The results are evaluated against experimental data available in the literature.

In aero-engine bearing chambers, the modelling of shear-driven oil films with the Volume of Fluid method poses significant challenges linked with the need to accurately capture the gas-liquid interaction at the free surface. Typically, the modelling of the latter relies on a dedicated scalable source term, which is activated locally at the interface between the phases. Our latest published work focused on the application of a popular term of this kind known as turbulence damping, and raised some questions on the suitability of the choice of a high value for its scaling factor. In this paper, a lower turbulence damping factor value is proposed. The new results are evaluated against both the reference bearing chamber experimental data and the previously published numerical data. The results highlight that a transition from shear-driven to gravity-driven flow conditions takes place once the damping factor value is decreased. Considering the impact this may have on the accuracy of the numerical predictions, a strategy is proposed towards a better-informed choice of the turbulence damping factor, in particular when the expected flow conditions are unknown.

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