Numerical simulation of polymer crystal growth under flow field using a coupled phase-field and lattice Boltzmann method

摘要

In the present study, the polymer crystal growth under the flow field is numerically simulated by using a coupled phase field (PF) and lattice Boltzmann (LB) method. Firstly, the phase field method is presented to capture the growth interface of polymer crystals, including the common morphologies of spherulite and shish-kebab crystallites. Then the lattice Boltzmann method is introduced to solve the viscous non-Newtonian flows of the polymer melt, where the half-way bounce back boundary condition is imposed with the aid of shape level-set (LS) function which is used to represent the crystal interface at each time. At last, the crystal growth for spherulites and shish-kebab crystallites under flow field is simulated by using the coupled PF–LB method, where the cross-WLF model is chosen to describe the melt viscosity. The effects of the flow velocity on the crystal morphologies, including single and multiple spherulite and shish-kebab crystallites, are analyzed in detail. The numerical results show that the flow velocity has an important impact on the crystal morphologies, and the crystals grow more faster towards the upstream direction, especially in the single and multi spherulites growth process.