Asymptotic theory of gas entrainment in a two-phase Couette flow

A gas film can be entrained when a liquid is forced to rapidly wet a substrate. In this work, we investigate the behavior of a two-phase flow in a Couette geometry, in which one plate is stationary and a gas film is entrained over the moving plate. We present an asymptotic theory of the selection of gas film thickness, based on lubrication approximations. It is found that the gas film thickness relies primarily on the curvature of the meniscus, which is determined by the balance between the capillary force and gravity. The influence of the plate speed on the gas film thickness follows the classical 2/3 power law analogous to liquid deposition, with a mild correction from the gas-liquid viscosity ratio. The asymptotic predictions agree well with the exact solutions of the lubrication equation.(c) 2022 Elsevier Masson SAS. All rights reserved.

Automated summary

In this study, an asymptotic theory of gas film thickness selection based on lubrication approximations is presented. It is found that the gas film thickness primarily depends on the curvature of the meniscus, determined by the balance between capillary force and gravity. The influence of plate speed on gas film thickness follows the classical 2/3 power law, with a mild correction from the gas-liquid viscosity ratio.