Liquid-Liquid Flow at Nanoscale: Slip and Hydrodynamic Boundary Conditions

Nonequilibrium molecular dynamics (NEMD) simulations have been performed to describe the flow of a fluid nanolayer confined by another fluid. The results show that the behavior of liquids can still be described by the Navier–Stokes equation at the nanoscale, i.e., when only a few molecular layers are involved. NEMD furthermore gives additional knowledge on flow. Indeed, while a very small slip is evidenced for a solid-liquid interface, e.g., in lubrication, the slip lengths are significantly larger at the liquid-liquid interface, as encountered, e.g., in droplet coalescence. The slip lengths of the two fluids are linked. The increase in hydrodynamic slip for liquid-liquid interfaces is attributed to the enhancement of fluid diffusion, which reduces friction.

^{Credit: L. Hilaire / CEA}

For more information, read the article by Lolita Hilaire, Bertrand Siboulet, Sophie Charton, and Jean-François Dufrêche in Langmuir 39, 2260 - 2273 (2023). DOI: 10.1021/acs.langmuir.2c02856