A Two-Phase Flow Solver with Variable Liquid Compressibility and Temperature Equation for Partitioned Simulation of Elastohydrodynamic Lubrication

TL;DR

This work develops a two-phase flow solver for elastohydrodynamic lubrication with variable liquid compressibility and a temperature equation, implemented by extending cavitatingFoam in OpenFOAM. It embeds a modular lubricant-model library (e.g., Tait/Doolittle/Carreau) and uses a homogeneous equilibrium model for cavitation, enabling density and enthalpy to depend on pressure and temperature and supporting partitioned FSI with a structural solver. The solver is validated on an EHL line-contact test and demonstrates that variable compressibility and thermal effects significantly influence pressure distribution, film thickness, and friction, especially under slip conditions. The approach leverages OpenFOAM, Kratos Multiphysics, and CoCoNuT to provide a flexible, extensible tool for high-pressure lubrication scenarios in challenging EHL conditions.

Abstract

This paper presents a new solver developed in OpenFOAM for the modeling of lubricant in the narrow gap between two surfaces inducing hydrodynamic pressures up to few gigapascal. Cavitation is modeled using the homogeneous equilibrium model. The mechanical and thermodynamic constitutive behavior of the lubricant is accurately captured by inclusion of compressibility, lubricant rheology and thermal effects. Different constitutive models can be selected at run time, through the adoption of the modular approach of OpenFOAM. By combining the lubricant solver with a structural solver using a coupling tool, elastohydrodynamically lubricated contacts can be accurately simulated in a partitioned way. The solution approach is validated and examples with different slip conditions are included. The benefit for the OpenFOAM community of this work is the creation of a new solver for lubricant flow in challenging conditions and at the same the illustration of combining OpenFOAM solvers with other open-source software packages.

Figures (15)

• Figure 1: Illustration of elastohydrodynamic lubrication.
• Figure 2: Flowchart illustrating the PIMPLE loop of the flow solver for use in a partitioned FSI approach to simulate EHL.
• Figure 3: Left part of the fluid mesh (yellow-green) and structural mesh (gray). Both are symmetric with respect to the $z$-axis.
• Figure 4: Partitioned coupling in each time step between the flow solver (OpenFOAM®) and the structural solver (Kratos Multiphysics) with the coupling tool CoCoNuT.
• Figure 5: The fluid mesh is divided into zones to obtain a proper meshing of the contact region. The right-bottom part is shown and the $x$-position of the zones is indicated relative to the roller radius (not to scale).