VISCOELASTIC EFFECTS ON THE STABILITY OF THIN-FILM PARALLEL FLOW IN LUBRICATION APPLICATIONS

摘要

The analysis is concerned with the effect of fluid-elasticity on the stability of laminar parallelrnflow. The widely used multi-grade oils contain polymer additives that make them viscoelastic.rnThese oils are widely used for high shear-rate laminar flow of hydrodynamic lubrication, wherernflow instability is undesirable because it significantly increases the viscous friction losses. Thernpractical objective of this theoretical investigation is to find out if polymer additives stabilize orrndestabilize the flow. . A fluid model is applied where the stress-relaxation effect is considered inrnaddition to the fluid viscosity. However, the normal stresses are disregarded.rnExtended Orr-Sommerfeld type analysis has been performed for elastic fluid films ofrnlubrication. The conclusion is that the elasticity of the fluid has a destabilizing effect. For parallelrnflow, the transition to instability is at lower Reynolds number in comparison to Newtonian fluids.