Crossover from Hydrodynamics to the Kinetic Regime in Confined Nanoflows

TL;DR

This study experimentally explores the transition from hydrodynamic to kinetic flow regimes in confined nanoflows, providing a comprehensive scaling function that unifies existing theories across different flow conditions.

Contribution

It introduces a new experimental mapping and a unifying scaling function that describes nanoflow behavior across hydrodynamic and kinetic regimes.

Findings

Developed a detailed experimental map of nanoflow regimes.

Constructed a scaling function unifying slip and viscosity theories.

Validated the scaling function across broad parameter ranges.

Abstract

We present an experimental study of a confined nanoflow, which is generated by a sphere oscillating in the proximity of a flat solid wall in a simple fluid. Varying the oscillation frequency, the confining length scale and the fluid mean free path over a broad range provides a detailed map of the flow. We use this experimental map to construct a scaling function, which describes the nanoflow in the entire parameter space, including both the hydrodynamic and the kinetic regimes. Our scaling function unifies previous theories based on the slip boundary condition and the effective viscosity.