Molecular kinetic modelling of confined fluid transport—a mesoscopic approach

Accurate modelling of confined fluid transport requires addressing the fluid-fluid and fluid-surface interactions across multiple scales, particularly when molecular sizes are comparable to the fluid mean free path and the confinement dimension. Advances in nanotechnology have sparked tremendous interest in the combined effects of non-equilibrium, real-fluid properties, and confinement on multiscale flows, where the Knudsen number or confinement dimension can vary widely. This review discusses molecular kinetic modelling approaches for: (1) fluid density ranging from dilute, where non-equilibrium effects dominate, to dense, where real fluid effects become critical; (2) flow domains ranging from macroscale to nanoscale, necessitating confinement-specific treatments; (3) fluid-surface interactions at various densities and confinements. The pronounced non-equilibrium and confinement effects introduce both intrinsic and apparent non-hydrodynamic effects, which require careful consideration in developing a molecular kinetic model.