A Model for Contaminant Transport, Aggregation and Deposition in Lubricated Contact of Rough Surfaces

Effective prediction of lubricated contact poses an especially challenging problem. On the one hand surfaces are non-smooth at micron-scale while, on the other hand, a lubricant contains varying degrees of impurities in form of particle contaminants. An accurate model for lubricated contact, therefore, must be able to account for the various interactions that include particle-fluid, particle-particle, fluid-rough surface, particle-rough surface and rough surface-rough surface interactions. In the current study we propose the use of Lattice Boltzmann Method (LBM) and JKR theory for elasto-adhesive contact to simulate the particle transport processes in a lubricant flow between two rough surfaces. A particle dynamics simulation method is proposed to predict the interaction of a group of particles. The particle-particle and particle-boundary interactions are modeled by an extension of the JKR theory in which viscoelastic interactions are included through the implementation of the Kelvin-Voigt stress-strain relations. The particle-fluid interaction is calculated from the LBM simulation. Time scale relations between LBM and particle dynamics are characterized. Simulation results show the effects of particle density and surface roughness on frequencies of particle-particle and particle-boundary impacts, particle deposition rate, particle cluster forming and fluid boundary pressure changes due to particle deposition. A parametric study is performed to elucidate the effect of rough surface geometry and the relative velocity of the surfaces on friction and lift. The results provide fundamental insight on the contamination effects on wear and life of lubricated surfaces.