Abstract
The thrust of this paper is to investigate theoretically the non-Newtonian couple stress squeeze film behaviour between oscillating circular discs based on V. K. Stokes micro-continuum theory. The lubricant squeezed out between parallel porous and rigid facings is supposed to be a concentrated suspension which consists of small particles dispersed in a Newtonian base fluid (solvent). The effective viscosity of the suspension is determined by using the Krieger-Dougherty viscosity model for a given volume fraction of particles in the base fluid. For low frequency and amplitude of sinusoidal squeezing where cavitation as well as turbulence are unlikely, the governing equations including the modified Reynolds equation coupled with the modified Darcy's equation are derived and solved numerically using the finite difference method and a sub-relaxed iterative procedure. The slip velocity at the porous-fluid interface is directly evaluated by means of the modified Darcy's law considering laminar and isothermal squeezing flow. For a given volume fraction, the couple stress effects on the squeeze film characteristics are analyzed through the dimensionless couple stress parameterℓ˜considering sealed and unsealed boundary of the porous disc. The obtained relevant results reveal that the use of couple stress suspending fluids as lubricants and the effect of sealing the boundary of the porous matrix improves substantially the squeeze film behaviour by increasing the squeeze film force. On the other hand, side leakage flow calculated in the sealed case remains constant in comparison to that of open end (unsealed) porous disc for all values of couple stress parameter and volume fraction of particle.
Highlights
The squeeze film lubrication mechanism is ubiquitous in many engineering applications such as gears, bearings in rotating and reciprocating machinery, and so on
The squeeze effect in lubrication occurs when positive pressure arises in a fluid film between two mutually approaching surfaces
This is due from the fact that the viscous fluid film cannot be squeezed out instantaneously, so it resists to extrusion which results in build-up of pressure
Summary
The squeeze film lubrication mechanism is ubiquitous in many engineering applications such as gears, bearings in rotating and reciprocating machinery, and so on. In his famous paper on lubrication, Osborne Reynolds [1] stated that the squeeze effect is an important mechanism, together with the wedge and stretching effects, for the self-generation of pressure in a lubricating film, especially when the contribution due to the wedge effect is small compared to the squeeze effect. This is due from the fact that the viscous fluid film cannot be squeezed out instantaneously, so it resists to extrusion which results in build-up of pressure
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