Contact Force Modeling in the Paper Forming Process

G. Kettil, F. Svelander, Master thesis, Chalmers University of Technology, supervisor A. Mark, examiner Anders Logg, June 2014.

Abstract

In simulation of paper forming it is of interest to understand the real world process to as great extent as possible. An important part is the interaction between objects in the fiber suspension, which makes the paper stay together. In this work the contact forces are modeled using the DLVO theory. It describes interactions between objects dispersed in a liquid through electrostatic and van der Waals forces.

When the distance between objects gets very small, the DLVO force formulas do not apply. Therefore an extended DLVO model is proposed, valid for all separation distances. It includes a repulsive force dependent on surface distance and the relative velocity of two interacting objects that is nonzero at small and negative separations. The repulsion is complemented by a function that dampens the velocity of objects that are close to going through each other. Dampings due to numerical issues are also proposed and implemented.

The proposed contact model has been successfully and robustly implemented in FCC’s (Fraunhofer-Chalmers Centre) Navier-Stokes solver IBOFlow and merged with the IPS ISOP Paper Forming software. Prior to this work no chemical interactions were included in the software model, why too many fibers unphysically slipped through the forming fabric during lay down.¬†From simulation results it is seen that the fibers stick to each other¬†after implementation of the extended DLVO model. This enables better retention of fibers on the forming fabric.

Authors and Affiliations

  • G. Kettil, Fraunhofer-Chalmers Centre
  • F. Svelander, Fraunhofer-Chalmers Centre



Photo credits: Nic McPhee