A general model for porous medium flow in squeezing film situations
TL;DR: In this article, a numerical investigation of the hydrodynamic lubrication of a porous squeeze film between two circular discs is presented. And the results show that the effect of the porous disc is to reduce the lubricating properties of the fluid film and this effect is increased during the squeezing action.
Abstract: The present paper deals with a numerical investigation of the hydrodynamic lubrication of a porous squeeze film between two circular discs. To this purpose, the thin film (reduced) Navier Stokes equations and a generalised porous medium model are solved. The numerical results show that the effect of the porous disc is to reduce the lubricating properties of the fluid film. This effect is increased during the squeezing action. In addition, it is shown that the film pressure, the load-carrying capacity and the velocity field based only on the Darcy model are predicted higher than those obtained from the generalised porous medium model. Copyright © 2009 John Wiley & Sons, Ltd.
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TL;DR: This study obtained p(HEMA) hydrogels with physicochemical and mechanical properties close to healthy articular cartilage, by introducing a hydrophilic monomer, namely acrylic acid (AA).
37 citations
TL;DR: In this article, the authors developed a new model of the interaction of a fluid film with a porous medium, taking into account the fluid inertia in both the lubricant and the porous matrix.
15 citations
TL;DR: In this paper, a coupled system of equations governing flow in the liquid film and the porous disk is analyzed and the loadbearing capacity for both configurations is also examined as a function of the permeability and geometry of the disk.
Abstract: Squeeze flows in liquid films between a porous disk and an impermeable disk generated by the relative motion of the disks are analysed. Two configurations that differ by the arrangement of (im)permeable external surfaces that bound the porous disk (i.e. not in contact with the liquid film) are considered. Such configurations allow for bearings with tuneable load-bearing characteristics and are also encountered in joint lubrication, adhesion, printing and composite manufacturing. In the present study, flow in the porous disk is governed by Darcy’s law and flow in the liquid film is described using lubrication theory. The present analysis also allows for slip between the liquid film and porous disk. Analytical solutions of the coupled system of equations governing flow in the liquid film and the porous disk are found. Under certain conditions, somewhat unexpected flow patterns are observed in the porous disk. The load-bearing capacity for both configurations is also examined as a function of the permeability and geometry of the permeable disk.
8 citations
TL;DR: In this paper, a quasi-static Darcy flow approach is used to estimate the initial porosity of a soft layer to minimize the peak impact force for impact squeeze between two perfectly rigid and impermeable flat disks of a highly compressible porous layer imbibed with Newtonian liquid.
7 citations
TL;DR: In this article, the elastic modulus of a highly compressible porous material, made of cellulose fibers, and imbibed with water, during stress relaxation tests on a rheometer, was shown that the material relaxes when kept at constant strain as long as there are open pores.
Abstract: The experimental study of a highly compressible porous material, made of cellulose fibers, and imbibed with water, during stress relaxation tests on a rheometer, shows that the material relaxes when kept at constant strain as long as there are open pores. Using the relaxation curves, the behaviour under compression can be divided into two distinct zones, a poro-elastic one and a purely-elastic one, bounded by the zero-porosity limit. In the poro-elastic zone, the "non-hookean" stress-strain curve is fitted using Spriggs' expression of the elastic modulus dependence with porosity. Therefore, the elastic modulus of the porous material is expressed as an exponential function with two parameters: the elastic modulus of the fibers and the initial porosity of the material. For the purely - elastic zone the variation of stress is expressed as a sum of the residual stress obtained from the continuity equation and a Hookean stress- strain variation of a thinner material with the elastic modulus of the fibers - determined previously. The relaxation curves are fitted with a relationship between the decay stress and time, approximated with three terms of Prony series expansion of the generalized Maxwell model.
4 citations
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TL;DR: In this paper, the viscous force exerted by a flowing fluid on a dense swarm of particles is described by a modification of Darcy's equation, which was necessary in order to obtain consistent boundary conditions.
Abstract: A calculation is given of the viscous force, exerted by a flowing fluid on a dense swarm of particles. The model underlying these calculations is that of a spherical particle embedded in a porous mass. The flow through this porous mass is decribed by a modification of Darcy's equation. Such a modification was necessary in order to obtain consistent boundary conditions. A relation between permeability and particle size and density is obtained. Our results are compared with an experimental relation due to Carman.
2,519 citations
TL;DR: The thermal dispersion conductivity tensor for convection in a porous medium is derived based on the method of volume averaging of the velocity and temperature deviations in the pores.
619 citations
TL;DR: In this article, a brief and simple account of continuum models for transport in porous media, and the role of length scales in passing from pore-scale phenomena to “Darcy” continuum scale representations using averaged variables.
Abstract: This article first provides a brief and simple account of continuum models for transport in porous media, and of the role of length scales in passing from pore-scale phenomena to “Darcy” continuum scale representations using averaged variables. It then examines the influence of non-Newtonian rheology on the single- and multi-phase transport parameters, i.e. Darcy viscosity, dispersion lengths and relative permeabilities. The aim is to deduce functional forms and values for these parameters given the rheological properties of the fluid or fluids in question, and the porosity, permeability, dispersion lengths and relative permeabilities (based on Newtonian fluids and equivalent capillary pressures) of the porous medium. It is concluded that micro-models, typically composed of capillary networks, applied at a sub-Darcy-scale, parameterised using data for flows of a well-characterised set of non-Newtonian fluids, are likely to provide the most reliable means.
213 citations