Numerical analysis of coating flows of concentrated dispersion system of disk-like particles using stochastic simulation

Abstract

Slot coating flows of concentrated dispersion systems of disk-like particles were numerically analyzed using a computational method that couples finite element computations of macro flows of the dispersion systems and micro simulations of the orientation behavior of the particles. The inter-particle interaction was included into the simulation using a Maier-Saupe type mean field potential function. The Brownian configuration field method was adapted to the computation of the particle motion for the reduction of computational costs. Furthermore effects of solvent evaporation from the free surface of a coated liquid film were considered in the present simulation. The potential strength was changed according to the particle concentration to consider the effect of solvent evaporation on the inter-particle interaction. The particles tended to orient just downstream of a slot die because of the elongation flow in this region, and the orientation relaxed as the particles flowed downstream. However, in a downstream region the orientation was fixed since the inter-particle interaction was intensified because of the increase in the particle concentration due to the solvent evaporation. The present simulation captured change in the orientation distribution of the particles due to the solvent evaporation and such information is useful for the process design of coating considering the relation between the particle behavior during the process and the function of products.