The effect of surface wettability on inertial pouring flows

TL;DR

This paper investigates how surface wettability influences inertial pouring flows, revealing a critical Weber number below which steady flow separation cannot occur, with analysis supported by simulations and experiments.

Contribution

It extends previous models by incorporating velocity profiles and capillary forces, providing a detailed analysis of flow separation dependent on wettability and edge sharpness.

Findings

Identification of a critical Weber number for flow separation

Dependence of critical Weber number on wettability and edge sharpness

Agreement with experimental trends

Abstract

A liquid poured from a curved solid surface can separate as a steady jet or sheet, or trickle down along the solid surface. It was shown by Duez et al. [Phys. Rev. Lett. 104, 084503 (2010)] that surface wettability controls the separation of an inertial flow from a solid surface to an unexpected degree, which was further motivated by an inertial-capillary adhesion model. In this paper we extend the analysis by a control volume calculation that takes into account the velocity profile within the flowing layer, supported by Boundary Integral potential flow simulations, and the detailed capillary forces induced by the local curvatures of the sheet. Our analysis captures the appearance of a critical Weber number below which no steady separated solutions can be sustained. We investigate the dependence of the critical Weber number on the wettability and sharpness of the edge of the curved solid, and recover the key experimental trends.