Abstract
Flows of complex fluids in a single-screw extruder were numerically simulated using a coupling method of continuum-mechanics-based computations for macroscopic flows and stochastic simulations for fluid mesoscale structures and the advantage of micro-macro simulations for complex fluids was investigated. In the present study, flows of polymer melts and dilute suspensions of disclike particles were considered and a simple model for the extrusion flow in which the flow is approximated by a shallow channel flow, was adopted. In the simulation for polymer melts, the Curtiss-Bird model was applied to represent the dynamics of polymer networks. The orientation behavior of polymers was analyzed and its dependence on the Weissenberg number was investigated. In addition, a low-cost method for plotting the distribution of orientation angle of polymers was proposed. In this method, additional stochastic simulation was performed at a sampling point in the flow field. The dependence of orientation angle on the gap wise position in an extruder was captured in more detail by this method. In the simulation of suspensions of disclike particles, a disclike particle was modeled by an oblate spheroid, and the motion of particles was computed using the stochastic differential equation for orientation vectors of oblate spheroids. The orientation behavior of particles was analyzed to find that the present approach is effective also for the suspension flows.
