On the fluid slip along a solid surface

TL;DR

This paper shows that fluid slip along a solid surface occurs under rapid relative velocity changes, challenging the common assumption of no-slip, and provides experimental estimates of slip length and conditions for slip.

Contribution

It demonstrates that fluid slip can occur during rapid velocity changes and estimates slip length and acceleration thresholds through droplet impact experiments.

Findings

Slip occurs when relative velocity change is rapid

Slip length can be estimated experimentally

Fluid acceleration is key to slip occurrence

Abstract

It is commonly assumed that fluid cannot slip along a solid surface. The experimental evidence generally supports this assumption. We demonstrate that when the change of the relative velocity of a fluid and a solid wall is sufficiently rapid, the slip does occur; the fluid is unable to adjust if acceleration is large enough, and it slips. We use droplet impact on a moving surface to demonstrate and estimate the slip length. We also estimate fluid acceleration, which is required to cause an observable slip.