Critical Capillary Number of Interfacial Film Displacement in a Capillary Tube

TL;DR

This paper investigates the critical capillary number governing interfacial film displacement in capillary tubes, analyzing how surface tension, wettability, and flow forces influence wetting dynamics through analytical and experimental methods.

Contribution

It introduces an analytical model for the critical capillary number considering contact angle, slip length, and capillary radius, validated by experiments.

Findings

Critical capillary number depends on contact angle, slip length, and radius.

Analytical model aligns with experimental data.

Wetting dynamics are governed by a balance of capillary and viscous forces.

Abstract

The role of surface tension and wettability in the dynamics of air-liquid interfaces during immiscible fluid displacement flows in capillary tube driven by pressure has been investigated. The contact angle and capillary number drive the force wetting processes which is controlled by the balance between the capillary and the viscous lubrication forces. The dynamic wetting condition with the critical capillary number is studied analytically and validated experimentally, which demonstrates that the critical capillary number is associated with the contact angle, slip length and capillary radius.