Pressure and shear flow singularities: Fluid splitting and printing nip hydrodynamics

Abstract

A numerical simulation of the fluid flow in the gravure printing nip, based on a discontinuous Galerkin algorithm, is used to study the fluid-splitting process and the transition between point and lamella splitting. We study the pressure and shear singularities at the contact point of the printing cylinder and substrate as a function of the variable microscopic residual gap and variations of the printing fluid quantities introduced to the nip. As the hydrodynamic boundary value problem is ill-defined by the nip singularity, we enhance the simulation using renormalization group and algebraic scaling techniques in order to obtain a numerically stable and physically meaningful prediction. Our simulations are compared to analytical results from lubrication theory and to experimental observations on a gravure press.