Forward Roll Film-Splitting: Theory and Experiment, 1994 Coating Conference Proceedings

D. F. Benjamin, M. S. Carvalho, T. J. Anderson, and L. E. Scriven

Liquid carried through the gap between counterrotating rolls ordinarily splits into two films, one on Roll 1 and one on Roll 2. Film-split ratios measured experimentally can be correlated by the power-law h2/h1 = a(V2/V1)^B, where h is film thickness, V is roll surface speed, and a and B are parameters that vary with circumstances. Past flow models based on the lubrication approximation support the correlation but do not predict the parameter variation. The Navier-Stokes theory of steady, two-dimensional viscous flow with free surfaces, including the effects of gravity, liquid inertia, and surface tension is used here to extend earlier work of Coyle et al. (1984, 1986) to probe the film-splitting flow fields in detail, and to evaluate the film-split parameters. The results are reinforced with new film-split measurements, and their relevance to multiple roll systems is remarked.