Wall slip effects in (elasto) hydrodynamic journal bearings

In recent years it has been shown experimentally by a number of workers that, for certain engineered surfaces, the no-slip boundary condition is not a valid one. Moreover, researchers demonstrate that like surface texturing, well-chosen slip/no-slip surface patterning can considerably improve the performance of fluid bearings.Firstly, a finite element analysis is proposed in order to study the influence of wall slip over the load carrying capacity and power loss in hydrodynamic fluid bearings. A systematic comparison is made with textured bearing conditions. A significant number of numerical simulations show that, comparing with the textured bearings, wall slip conditions lead to better power loss improvements. Concerning the load capacity, the two solutions can lead to similar improvements, but only for specific surface patterns. Also, particular care must be taken in choosing the texture/slip zone geometry because an inappropriate choice can lead to a drastic deterioration of the bearing performance, especially in relation to load-carrying capacity.Secondly, the study is extended to the influence of wall slip in highly loaded compliant bearings, for steady-state and dynamical load conditions. The predictions show that well-chosen slip/no-slip surface pattern can considerably improve the bearing behaviour and largely justify future numerical and experimental works.

► Described the methodology used to derive an extended form of the Reynolds equation, capable to include wall slip boundary conditions.
► Significant number of numerical simulations have been performed to compare the effects of wall slip conditions with the effects of surface texturing.
► The case of an ICE engine bearing with slip/no-slip surface patternis investigated in steady-state and dynamically loaded conditions.