Pacification of thermocapillary destabilization of a liquid film in zero gravity through the use of an isothermal porous substrate

TL;DR

This study investigates how using a porous substrate can suppress thermocapillary instabilities in thin liquid films in zero gravity, thereby preventing rupture and extending film lifespan.

Contribution

It demonstrates that a porous substrate dampens destabilizing modes, significantly prolonging the stability of liquid films in zero gravity conditions.

Findings

Porous substrates prevent film rupture in zero gravity.

Destabilizing modes are damped by the porous medium.

Film lifespan is significantly extended with porous substrates.

Abstract

Thin liquid films on isothermal substrates, where film is flat and parallel to the substrate, succumb to thermocapillary instabilities and rupture forming local hot-spots. These instabilities are called long wavelength instabilities and are specific to aspect ratios where the liquid film mean thickness is several orders of magnitude less than the substrate characteristic dimension. In the absence of stabilizing gravitational acceleration, the growth rate of thermocapillary instabilities is further intensified, driving the film to rupture at an even earlier time. Numerical simulations of zero gravity dynamics of Newtonian liquid films on a solid, horizontal, isothermal substrate are conducted. When the solid, isothermal substrate is replaced with one that possesses one- dimensional porosity, is fully saturated with the same fluid as that of the liquid film and is deep enough to accommodate all of the liquid on it, it is observed that destabilizing spatial modes are damped thereby preventing rupture and the film lifespan is prolonged. This nonlinear evolution is visualized and quantified using recurrence plots.