In this simplified geometry, the piston drives the plug-like flow of the confined liquid column, and the driving force is balanced by the liquid/solid friction. To simulate the influence of nearby solid/solid contacts on the liquid/solid friction, we propose a simplified mode for the contacts among surface asperities, described as a movable driving piston (Fig. Here we used molecular dynamics (MD) simulations to address this issue through simulating flows of Lennard–Jones (LJ) chain-like liquid encaged in a solid cylindrical nanopore with atomically smooth surfaces. g., what is the flow behavior for fluid entrained between colliding asperities, in particular for the confined film having a thickness of molecular dimension? Some important questions in understanding mixed lubrication remain unsolved, e.

Compared to hydrodynamic lubrication, predicting mixed lubrication is rather difficult, because it includes the complex interaction among solid/solid contact, space confinement and fluid/solid friction. At present, we have only a very limited understanding of the mixed lubrication region.

The key feature of mixed lubrication is that both hydrodynamic lubrication and asperity contacts have to be present simultaneously. The lubrication regime between boundary lubrication and hydrodynamic lubrication is termed as partial lubrication or mixed lubrication. Many practical systems, such as wear, micropitting, and scuffing, operate under the particular region of liquid lubrication called mixed lubrication. The liquid/solid frictions become much more complicated by the occurrence of solid–solid contacts. Even for one of the simplest systems, i.e., a nonpolar molecular liquid, confined between two atomically smooth surfaces of a distances below 10 nm, reported measurements of friction span from superlubricity to moderate or high friction. When reducing the system size to the nanoscale, fundamental questions regarding the liquid–solid friction and shear properties remain unclear. In the nanoscale regime, transport properties show strong qualitative deviations from their bulk counterparts. The dynamics of nanoconfined liquids are essential to various processes such as lubrication, filtration, energy storage and other biological scenarios.

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