Studies on the Pressure Buildup and Shear Flow Factors in the Cavitation Regime

Modeling tribological contacts is commonly based on the Reynolds equation. This study discusses the validity of conventional, averaged Reynolds simulations for systems including starvation regimes. Two fundamental assumptions that are used as common practice in many elasto-hydrodynamic (EHD) calculations, are debated. First, the use of a cavitation pressure (in most cases assumed to be zero) independent of the microscopic roughness. Second, the application of a shear flow factor, which is determined on a microscopic scale with a fully filled gap. The validity of these two assumptions is analyzed with simulations on the microscopic scale. For this purpose, simulations of partially filled contacts are carried out using the partially filled gaps model developed by the authors. The topographies, the filling level and the fluid distribution were varied. The simulations comply with established models for the fully filled state and show a distinct behavior for partial filling and different fluid distributions. Neglecting the contribution to pressure buildup and shear flow of partially filled domains is a valid method in most cases. However, as this study shows, near the fully filled regime, the domains should be handled with care.