Parametric Study of the Flow in Printing and Coating Nips: The Influence of non-Newtonian Fluids

The changes in flow through nip contacts will significantly affect coat weight and print colour. The evaluation of the performance of printing and coating nips is a generic problem for many industrial applications. Previously this has been modelled using boundary element methods [I], [2] for Newtonian fluids. However, within these nips high shear rates are generated and these will affect the viscosity and subsequent performance of the nips for non-Newtonian fluids. A power law fluid model has been used to model the shear rate to viscosity relationship. The model results quantify the changes in pressure, film thickness and flow rate that can occur when changing the fluid properties, for example the viscosity, degree of shear thinning. It is successfully applied to a number of different system geometries.