Surface Ribbing of a Thin Viscous Fluid Film Emerging From a Spreader or Roller

Abstract

The thin film produced by the flow of a viscous fluid through a narrow gap between a spreader (or roller) and a flat plate is often subject to surface ribbing. A linear perturbation analysis, based upon lubrication theory, is used to examine the nature of this ribbed film and, specifically, to explain the large distances over which ribbing is observed to prevail. Taking into account the effects of both surface tension and gravity in smoothing out the film, the analysis predicts a characteristic distance from striated film-rupture to where a uniform film is formed.