Dynamics of thin liquid films on a porous substrate in zero gravity

TL;DR

This paper investigates the long-wave dynamics of thin liquid films on isothermal porous substrates in zero gravity, revealing how porosity influences thermocapillary structures and film stability over time.

Contribution

It compares the evolution of liquid films on porous and non-porous substrates in zero gravity, highlighting the damping effect of porosity on thermocapillary structures.

Findings

Porous substrates damp secondary thermocapillary structures.

Primary structures persist longer without rupture on porous substrates.

Porosity influences the time scales of film evolution.

Abstract

The long-wave dynamics of liquid films on isothermal substrates show a dynamic competition between various physical mechanisms. If the destabilizing effect of thermocapillarity overcomes the stabilizing effect of surface tension and gravity, the liquid film ruptures in finite time, through the formation of primary and secondary thermocapillary finger structures. The long-wave evolution dynamics are compared for two different substrate types: isothermal non-porous and isothermal porous for small Biot number in a zero gravity environment. The multi-time-scale dynamics is revealed through time scales obtained from a method of similarity solutions. It is observed that with an isothermal porous substrate, in zero gravity, secondary thermocapillary structures are damped through imbibition and that primary thermocapillary structures persist for long times without rupture.