Asymptotic decay and non-rupture of viscous sheets

TL;DR

This paper proves that viscous thin liquid sheets decay exponentially to flatness over time and cannot rupture in finite time without external forces, confirming a long-standing physical conjecture.

Contribution

It establishes exponential decay and non-rupture results for viscous sheets using PDE analysis and Lagrangian transformations, confirming a physical conjecture.

Findings

Solutions decay exponentially to flat profile

Viscous sheets cannot rupture in finite time without external forcing

Special initial data lead to exponential decay even without surface tension

Abstract

For a nonlinear system of coupled PDEs, that describes evolution of a viscous thin liquid sheet and takes account of surface tension at the free surface, we show exponential $(H^1,\,L^2)$ asymptotic decay to the flat profile of its solutions considered with general initial data. Additionally, by transforming the system to Lagrangian coordinates we show that the minimal thickness of the sheet stays positive for all times. This result proves the conjecture formally accepted in the physical literature [1], that a viscous sheet can not rupture in finite time in absence of external forcing. Moreover, in absence of surface tension we find a special class of initial data for which the Lagrangian solution exhibits $L^2$-exponential decay to the flat profile.