Simulation of roll coating process using FEMLAB

Manski, S.S.1, Mmbaga, J.P.1, Hayes, R.E.1, Bertrand, F.H.2, Tanguy, P.A.2
1 Department of Chemical and Materials Engineering, University of Alberta, Edmonton AB Canada
2 URPEI, Department of Chemical Engineering, Ecole Polytechnique, Montreal, Quebec, Canada

Paper coating operations involve a number of coupled multiphase interactions. The use of FEMLAB to study these coupled phenomena using a level set method is reported. Several problems, including the penetration of fluid into a porous media, flow split meniscus dynamics and entrapment of air bubbles during coating process are explored using a level set implementation. Fluid penetration from a rectangular channel into a porous paper sheet was successfully implemented using FEMLAB.

The penetration depths obtained by applying the level set method on a relatively large computational domain shows a dependence on the permeability of the porous medium and the pressure applied at the paper surface. The fluid flow in the application nip of the film coater involves numerous free surfaces which represent the interface between the liquid and surrounding air. The free surface locations, including meniscus profiles and the corresponding split point coordinates are computed using the level set method.

Comparison with a singl phase flow solution is provided. Air entrainment in the application nip can cause spitting at the exit. To capture this phenomenon requires the ability to track the motion of bubbles in a fluid under imposed flow. The level set method in FEMLAB-MATLAB environment is shown to have a great potential for multiphase interactions in paper coating.