Pressure Gradient Induced Boundary Slippage Influence on the Contact Mixing with Boundary and Hydrodynamic Fluid Films

The present paper analytically investigates the influence of the boundary slippage on the performance of the contact mixing with boundary and hydrodynamic fluid films. The contact is one-dimensional composed of two parallel plane surfaces, which are respectively rough rigid with rectangular projection in profile and ideally smooth rigid. In the outlet zone of the contact occurs boundary films and in the inlet zone of the contact occurs conventional hydrodynamic fluid films. The boundary slippage occurs at both of the contact surfaces in the boundary film area due to the limited shear stress capacity of the film-contact interface at these contact surfaces and the high pressure gradient in the boundary film area. The viscosity and density of the boundary film are varied across the film thickness due to the boundary film-contact interactions and their effective values are used in modeling which depends on the boundary film thickness. The boundary film-contact interfacial shear strength is formulated as dependent on the boundary film pressure and thickness. The hydrodynamic fluid film does not slip at either of the contact surfaces. The boundary pressures at the edges of the contact, which are used as the boundary conditions in analysis, are respectively taken as low, medium and high. The results of the boundary slippage influence on the mass flow through the contact, the contact pressure and the contact load-carrying capacity are presented for different operating conditions.