Browsing by Author "Videman, Juha H."
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- Lubrication approximation for fluids with shear-dependent viscosityPublication . Pereira, Bruno M. M.; Dias, Gonçalo A. S.; Cal, Filipe S.; Rajagopal, Kumbakonam R.; Videman, Juha H.We present dimensionally reduced Reynolds type equations for steady lubricating flows of incompressible non-Newtonian fluids with shear-dependent viscosity by employing a rigorous perturbation analysis on the governing equations of motion. Our analysis shows that, depending on the strength of the power-law character of the fluid, the novel equation can either present itself as a higher-order correction to the classical Reynolds equation or as a completely new nonlinear Reynolds type equation. Both equations are applied to two classic problems: the flow between a rolling rigid cylinder and a rigid plane and the flow in an eccentric journal bearing.
- On the lubrication approximation for a class of viscoelastic fluidsPublication . Cal, Filipe S.; Dias, Goncalo A. S.; Pereira, Bruno Miguel M.; Pires, Gabriel E.; Rajagopal, K. R.; Videman, Juha H.We present a rigorous derivation of a dimensionally reduced Reynolds type equation for thin film flow lubrication of a class of viscoelastic fluids by employing a perturbation analysis on the upper-convected Maxwell model in natural orthogonal coordinates. This approximation accounts for the viscoelastic and curvature corrections to the classical Reynolds lubrication approximation. Comparison of our approximation with the classical Reynolds approximation suggests that viscoelasticity can have a significant influence on the lubrication characteristics, at least for certain values of the film thickness and of the eccentricity ratios of the journal bearing