ABSTRACT
The performance of particular types of seals is governed by the flow resistance of a sealing interface gap that is very small by normal engineering standards. Floating bushing seals, for example, are tailored to form a clearance of about 10 μm; rubber hydraulic seals and mechanical seals may slide on a self-generated liquid film less than 1 μm thick. This chapter discusses some physical and mathematical aspects of the prediction of flow in seal interfaces. A measure of cohesion is the dynamic viscosity η of the fluid. When viscous forces are dominant in a flowing liquid, neighboring streamlines are parallel and the flow is laminar. Both the criterion of transition from laminar to turbulent flow and the mathematical basis of laminar flow calculation are connected with the name of Osborne Reynolds. The transition is characterized by the Reynolds number Re while the flow parameters are interrelated by the Reynolds equations.
