Computational modelling of fluid transport in poroelastic interfaces

Porous interfaces are ubiquitous in nature. Their load bearing capacity, typical of e.g. articular cartilage, has often been exploited by engineers to develop porous bearings, whose design and operation must account for the flow of the lubricating medium through the contacting interface. Improper fluid transport to a porous bearing can damage its internal network and lead to operational failure. Depending on the operating conditions, the bearing transitions between boundary and hydrodynamic lubrication regimes. To accurately understand fluid flow behaviour, both the porous bearing and the lubricating fluid must be analysed as a coupled system. In this work, we developed a new fluid–solid coupled soft porous bearing model that can be used to study all lubricating conditions, analyse the fluid flow pattern, and evaluate the function and load bearing capacity of the porous interface. We also propose an approximate relation between flow factors and permeability, which captures the sealing effect that contacting asperities introduce and is used to incorporate varying permeability along the contact interface. Additionally, the model takes into account surface roughness and both fluid and solid pressures in the film thickness calculation. This coupled approach offers key insights into the interplay between the flow of the lubricant into the porous medium and the fluid film by predicting when the lubricant begins to enter the porous bearing and by explicitly capturing interactions in the contact region through which it interacts with the porous network. The model predicts a non-linear increase in fluid flow into the bearing as the porous bearing operates in the hydrodynamic regime. Overall, this numerical model provides a deeper understanding of fundamental lubrication mechanisms and serves as a valuable tool for analysing and designing soft bearings for industrial and biomedical applications, including human joints.