Film‐splitting flows of shear‐thinning liquids in forward roll coating

Asymmetric film-splitting of shear-thinning liquid between rotating cylinders in forward roll coating is analyzed with the Carreau model of shear-sensitive liquid. The mass and momentum conservation equations for steady, two-dimensional flow are solved by means of the Galerkin finite-element method. A simpler model is also developed from the lubrication approximation and its range of validity is established. The major results are that the greater the shear thinning, the farther out of the gap the splitting meniscus moves, the higher the flow rate through the gap, and the more symmetrical the film split than with Newtonian liquid. Experiments reported in the literature confirm some of these predicted trends.