Numerical Simulation of Multi-Scale Oil Films on a Rotating Cup Using VOF and Coupled Eulerian Thin-Film-DPM Approaches

Abstract

In this study, the newly developed Nottingham Gas Turbine and Transmission Research Centre (G2TRC) Bearing Chamber Test Module is presented and investigated computationally. The module houses a rotating cup and shaft configuration in order to simulate the droplet generation processes from an aeroengine bearing. The objective of this paper is to model the thin film that develops over the rotating cup surface, comparing a high-fidelity Volume of Fluid (VOF) approach against the Eulerian Thin-Film Model (ETFM). Whilst a VOF approach has previously demonstrated good accuracy for modelling of films over a rotating surface, the ETFM can provide a comparable solution at a much-reduced computational cost. Simulations are performed over a range of shaft speeds and oil flow rates to represent engine operating conditions. This study presents the very first simulation of an oil film over a rotating cup geometry, with a shaft running through the centre of the cup. Computationally, a VOF periodic sector is compared to ETFM simulations run on an equivalent 30° periodic domain. At planes before the rotating cup edge, both film thicknesses and axial velocities are compared. The high-fidelity VOF simulations demonstrate that with an increase in rotational speed, the film thickness over the rotating cup reduces; whilst an increase in oil flow rate produces a thicker film. Compared to the high-fidelity VOF simulations, the ETFM provides good agreement in terms of both film thickness and axial velocities. Overall, the ETFM is shown to be able to produce a similar film to the VOF approach at a much-reduced computational cost, offering a numerical speed-up of approximately 200 to 300 times.