Three-Dim. Modeling of a Twin-Screw-Extruder w. IB Method

The twin-screw extruder (TSE) is one of the most important machines used for processing polymers, chemicals, and foodstuff. Despite many different designs, TSEs are particularly effective in transporting and mixing highly viscous materials in a continuous way. The screws are made of elements having different geometries, each one fulfilling a different purpose; for example, conveying elements transport the material forwards, while kneading elements are used to strain and mix it. The design and optimization of TSE by means of experimental prototypes is expensive and time-consuming. The use of numerical simulations to predict the behaviour of TSE can substantially speed-up the development phase and, compared to experimental studies, many more configurations can be considered in detail and at lower cost. Furthermore, simulation methods can help increasing the understanding of the complex interactions between operating conditions, material properties and screw geometries. The goal of this project consists in developing a novel Immersed Boundary (IB) Method for the numerical simulation of TSEs. This approach allows the resolution of the fluid flow around complex bodies such as the overlapping screws of an extruder. The medium filling the device is assumed to be a single-phase Newtonian (e.g., silicon oil) or non-Newtonian fluid (e.g., molten polypropylene). The model is validated with the aid of experimental measurements performed on a custom-build rotating rheometer and on a real twin-screw extruder. The numerical method is implemented in the CFDEMcoupling software and maintained for the entire duration of the project.