A Model for Wall Slip Prediction of Confined n-Alkanes: Effect of Wall-Fluid Interaction Versus Fluid Resistance

Savio, Daniele; Fillot, Nicolas; Vergne, Philippe; Zaccheddu, Maurizio

doi:10.1007/s11249-011-9911-6

Cited by 64 publications

(106 citation statements)

References 37 publications

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“…These simulations have shown that the slip length generally increases with increasing sliding velocity and pressure [168][169][170][171]. At very high sliding velocity, the slip length asymptotes towards a constant value [57].…”

Section: Boundary Slipmentioning

confidence: 85%

“…Boundary slip occurs when the fluid cohesion is relatively stronger than its adhesion to the sliding surfaces [105], meaning that the surfaces do not transfer sufficient momentum to fully shear the fluid [168]. This can lead to large reductions in friction compared to the Couette case [146].…”

Section: Boundary Slipmentioning

confidence: 99%

“…This can lead to large reductions in friction compared to the Couette case [146]. Slip has been commonly observed in NEMD simulations of thin fluid films confined between atomically-smooth surfaces [57,[168][169][170][171]. Many of these studies have quantified the slip length, which is defined as an extrapolated distance into the wall where the tangential velocity component vanishes (see Fig.…”

Section: Boundary Slipmentioning

confidence: 99%

“…Slip lengths extracted from NEMD simulations have been fed into a modified Reynolds equation to study the effect of slip at one [182] or both [168] of the surfaces on flow behaviour, film thickness, and EHL friction. These results have shown that slip can lead to a significant reduction in friction and film thickness compared to the no-slip case, particularly at high shear rates.…”

Section: Boundary Slipmentioning

confidence: 99%

“…This method is relatively straightforward to implement, but requires careful planning to establish which regions of phase space can be reliably probed with MD to provide useful inputs for the continuum models. For example, Martini et al [160] and Savio et al [168,182] respectively used local viscosity and slip information obtained using MD simulations to improve continuum predictions of film thickness and friction for strongly confined systems. These are examples of phenomena that can be studied at a single relevant scale and integrated at a larger scale in a hierarchical manner.…”

Section: Linking MD To Larger Scalesmentioning

confidence: 99%

See 4 more Smart Citations

Advances in nonequilibrium molecular dynamics simulations of lubricants and additives

2018

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Nonequilibrium molecular dynamics (NEMD) simulations have provided unique insights into the nanoscale behaviour of lubricants under shear. This review discusses the early history of NEMD and its progression from a tool to corroborate theories of the liquid state, to an instrument that can directly evaluate important fluid properties, towards a potential design tool in tribology. The key methodological advances which have allowed this evolution are also highlighted. This is followed by a summary of bulk and confined NEMD simulations of liquid lubricants and lubricant additives, as they have progressed from simple atomic fluids to ever more complex, realistic molecules. The future outlook of NEMD in tribology, including the inclusion of chemical reactivity for additives, and coupling to continuum methods for large systems, is also briefly discussed.

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Section: Boundary Slipmentioning

confidence: 85%

Section: Boundary Slipmentioning

confidence: 99%

Section: Boundary Slipmentioning

confidence: 99%

Section: Boundary Slipmentioning

confidence: 99%

Section: Linking MD To Larger Scalesmentioning

confidence: 99%

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Advances in nonequilibrium molecular dynamics simulations of lubricants and additives

2018

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Molecular Dynamics Simulations on the Flow Behavior of 5CB Liquid Crystal Sandwiched Between Iron Walls

Chen

Sun

Xiao

et al. 2022

Advcd Theory and Sims

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The 4-n-pentyl-4′-cyano biphenyl (5CB) liquid crystal (LC) sandwiched and sheared between atomically flat and grooved iron walls, respectively, is simulated using molecular dynamics, and the flow behavior of the system under confinement, pressure, and shear is investigated. The order parameter P 2 , velocity, and density of 5CB are profiled as a function of distance from the walls using a block analysis method. The flow-alignment phenomenon is reproduced, and alignment angles ranging from 11.3°to 13.9°are observed. The competition between the elastic effect of the surface and viscous effect of the flow on the orientation of the 5CB molecules is investigated. The P 2 of 5CB located in the vicinity of the grooved walls is higher than that of the flat walls, while this difference is negligible in the case of 5CB distanced from the walls. Instead of boundary slip or Couette flow, the velocity profiles reveal a boundary condition (BC) of central localization, which is very different from the assumed Couette flow BC in most analytical models of LC flow. This work enhances the current molecular-scale understanding of the flow behavior of confined liquid crystals and provides additional insights into the phenomenon.

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Tribological Design by Molecular Dynamics Simulation: Influence of the Molecular Structure on Wall Slip and Bulk Shear

Mehrnia

Pelz

2022

Chem Eng & Technol

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The tribological properties of a complex branched‐hydrocarbon oil under shear in a gap between smooth iron atom surfaces were studied by large‐scale molecular dynamics (MD) simulation. The liquid was a nonpolar lubricant, i.e. a polyalphaolefin (PAO) oil mixture of 1‐decane dimer, trimer, and tetramer molecules. The rheological characteristics of the lubricant, including the shear stress and viscosity as well as the relaxation time of the liquid molecule, were calculated. The results show that, as the number of branches of the liquid molecule increases, the shear stresses and the wall slip increase. However, for a mixture fluid containing three different branched molecules, the wall slip decreases in comparison to a liquid consisting of only one kind of branched molecule.

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A Model for Wall Slip Prediction of Confined n-Alkanes: Effect of Wall-Fluid Interaction Versus Fluid Resistance

Cited by 64 publications

References 37 publications

Advances in nonequilibrium molecular dynamics simulations of lubricants and additives

Advances in nonequilibrium molecular dynamics simulations of lubricants and additives

Molecular Dynamics Simulations on the Flow Behavior of 5CB Liquid Crystal Sandwiched Between Iron Walls

Tribological Design by Molecular Dynamics Simulation: Influence of the Molecular Structure on Wall Slip and Bulk Shear

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