Predictions of Falling Wavy Films Based on the Depth Averaged Thin Film Model and Its Application to Aeroengine Bearing Chamber

Abstract In the present study, the evolution of a falling wavy film with upstream forced excitation is investigated using the depth averaged thin film model, known as Eulerian Thin Film Model (ETFM). Because of the depth averaging of the governing equations, coarse grids can be used in the wall normal direction. Consequently, this model is computationally efficient when compared to fully resolving thin films and hence highly advantageous for industrial simulations. In the case of a falling wavy film, film thickness and film velocity are closely coupled. A coupled solver that solves the depth averaged continuity and momentum equations simultaneously has been implemented with the provision to apply smoothing to the curvature of surface tension term to improve the accuracy and robustness of the model. The implemented model provides a stable solution for explicit as well as implicit temporal formulations. The performance of the newly implemented ETFM model is evaluated by comparing numerical results with experimental measurements and high-fidelity VOF simulations. The newly implemented model is found to be reliable in predicting free surface film profiles. It is 150 to 415 times computationally cheaper when compared to high-fidelity VOF simulations. The implemented and validated model is successfully used to predict a wavy film on the inlet of a representative aeroengine bearing chamber. The model is able to capture key flow physics on the front face of a static insert, which forms part of the bearing chamber inlet, and agrees well with experimental visualization of oil flow on the insert.