Abstract
The analysis is concerned with the effect of fluid-elasticity on the stability of laminar parallel flow. The widely used multi-grade oils contain polymer additives that make them viscoelastic. These oils are widely used for high shear-rate laminar flow of hydrodynamic lubrication, where flow instability is undesirable because it significantly increases the viscous friction losses. A fluid model is applied where the stress-relaxation effect is considered in addition to the fluid viscosity. However, the normal stresses are disregarded.
Extended Orr-Sommerfeld type analysis has been performed for elastic fluid films of lubrication. The conclusion is that the elasticity of the fluid has a destabilizing effect. For parallel flow, the transition to instability is at lower Reynolds number in comparison to Newtonian fluids.
