Multi-scale soft porous lubrication

This study is about the lubrication of a long porous slider in which the fluid is injected into the porous bottom. The similarity transformation reduces the Navier-Stokes equations to couple nonlinear, ordinary differential equations, which are solved by a new algorithm. The proposed technique is based on integral transformation. Apparently, there is great symmetry between proposed method and variation iteration method, Adomian decomposition method but in integral transform method all the boundary conditions are applied, then a recursive scheme is used for the analytical solutions, which is unlike the Variational Iteration Method, Adomian Decomposition Method, and other existing analytical methods. Solutions are obtained for much larger Reynolds numbers, and they are compared with analytical and numerical methods. Effects of Reynolds number on velocity components are presented.

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“…By using software MATHEMATICS, we calculated first two terms for readers' reference, which are as follows 5 10 − 33η 6 5 + 144Rη 5 5…”

Section: Appendix Amentioning

confidence: 99%

“…Kumar analyzed a porous elliptical slider with a semi-analytical technique [5]. Zhu studied multi-scale soft porous lubrication [6]. Lang investigated theoretical and experimental study of transient squeezing flow in a highly porous film [7].…”

Section: Introductionmentioning

confidence: 99%

Integral Transform Method to Solve the Problem of Porous Slider without Velocity Slip

Faraz

Khan

et al. 2019

Symmetry

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“…Under startand-stop conditions (e.g., windscreen wipers [8,9]) or after long and severe operation, the lubricant regime is more likely to be mixed or boundary lubricated, depending on the quantity of lubricant still present in the pores. More generally, the lubrication mechanisms occurring in soft contacts were extensively studied in [10,11]. These findings have improved the understanding of lubrication theory of porous contacts and can aid the design of new porous material combinations in sliding contact.…”

Section: Introductionmentioning

confidence: 97%

Identification of a Material–Lubricant Pairing and Operating Conditions That Lead to the Failure of Porous Journal Bearing Systems

2020

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In this study, we perform accelerated wear tests with porous journal bearings (PJBs) on a lab test rig, providing statistically reliable results under realistic operational conditions. To this end, a custom-made tribometer consisting of 5 mechanically independent but centrally controlled units was used to test five identical bearings in parallel. The test parameters were tuned to promote enough wear under mixed lubrication by increasing the clearance gap and the radial load, while minimizing the bidirectional rotational speed. A wide range of lubricant and material combinations were evaluated, the vast majority of which performed excellently (i.e., negligible wear and low friction). Only one notable combination of a low-density iron bearing paired with a standard PAO-based lubricant failed when operating at low rotational speeds, exhibiting highly unstable frictional behavior and 10–20 times the typical wear in practical applications. An analysis of Stribeck curves, recorded periodically during the wear tests as a diagnostic tool, proved that this particular combination of materials and parameters failed to run in properly, with deteriorating tribological behavior over time. A direct relation between the total wear and the maximum temperature in the tribocontact during testing helped identify this pairing as the only one operating solely under mixed lubrication (high asperity contact), explaining the excessive wear. Graphical Abstract

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“…24 A similar approach is also used at the fracture-matrix boundary in fractured porous media. 25,26 Many other problems where the boundary with a porous medium plays a central role have been recently investigated, like, for instance, flow near a porous membrane, 27 lubrication in the presence of a porous material, 28,29 or coupling with mass transport. 30 So far, however, a unified methodology to provide a macroscopic flow description in the bulk of a porous medium and close to its boundary, whatever its nature and shape, is still lacking, albeit of valuable interest.…”

Section: Introductionmentioning

confidence: 99%

Flow near porous media boundaries including inertia and slip: A one-domain approach

Valdés‐Parada

Lasseux

2021

Physics of Fluids

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This work addresses the macroscopic modeling of flow near porous media boundaries. This includes the vicinity with a fluid channel (i.e., a fracture), another rigid porous medium, or an impervious non-deformable solid. The analysis is carried out for one-phase, steady, incompressible, inertial, and isothermal flow of a Newtonian fluid, considering slip effects at the solid-fluid interfaces. A one-domain approach is proposed, employing a simplified version of the volume averaging method, while conceiving the system as two homogeneous regions separated by an inter-region. The upscaling procedure yields a closed macroscopic model including a divergence-free average (filtration) velocity for the mass balance equation and a unique momentum equation having a Darcy structure. The latter involves apparent permeability tensors that are constant in the homogeneous regions and position-dependent in the inter-region. All the permeability tensors are determined from the solution of coupled closure problems that are part of the developments. The derived model is validated by comparisons with direct numerical simulations in several two-dimensional configurations, namely, two porous media of contrasted properties in direct contact or separated by a fracture, the boundaries being either flat or wavy and a porous medium in contact with a flat or corrugated solid wall or separated from the latter by a fluid layer. The simplicity and versatility of the derived model make it an interesting alternative to existing one-and twodomain approaches developed so far.v Ã

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Multi-scale soft porous lubrication

Cited by 12 publications

References 26 publications

Integral Transform Method to Solve the Problem of Porous Slider without Velocity Slip

Integral Transform Method to Solve the Problem of Porous Slider without Velocity Slip

Identification of a Material–Lubricant Pairing and Operating Conditions That Lead to the Failure of Porous Journal Bearing Systems

Flow near porous media boundaries including inertia and slip: A one-domain approach

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