This work concerns numerical simulation of free‐surface flows of highly viscous liquids in single‐screw extruders.The numerical treatment of a partially filled extruder is a challenging task due to the complex geometry and the large differences in density and viscosity between the two phases, e.g. polymer melt and air. Furthermore, the rotation of the screw leads to a continuous renewing of the free‐surface. For this purpose the Volume of Fluid (VOF) method is used. First a simplified two‐dimensional model of a single‐screw extruder is considered. Good agreement is obtained between the numerical results and experimental data. Finally, the three dimensional free‐surface flow in a partially filled single‐screw extruder with dynamic mesh motion is presented. In addition, the power characteristics of a conveying screw element with varying degree of filling is discussed. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

This work deals with the modelling and simulation of a degassing process mainly used for extruders in polymer industry. The numerical simulations are done with finite-volume method using OpenFOAM for a 2D single screw extruder. The material parameters have been all chosen for a PDMS-Pentane polymer mixture so that the results could be compared with the available experiments already performed for this mixture [1]. In addition to experiments, the numerical results will be compared with an analytical solution derived from Danckwerts' model [2] [3].

In this work we present the free-surface flow of high viscous Newtonian liquids in a simplified extruder model, namely the flat-plate model. Due to high density and viscosity ratios, a free-surface approach based on the volume of fluid method is used. The material distribution for different degree of fillings and the resulting power consumption is investigated. In addition, the obtained power characteristic is compared against analytical consideration and numerical simulation of a fully filled case. The investigation shows that the power characteristic of a partially filled extruder can be estimated by a fully filled computation.

This study describes the free-surface flow of a highly viscous liquid between two concentric cylinders. In the process the morphology of the phase boundary is determined using a straight volume of fluid approach. Due to large differences in viscosity the gaseous phase is considered as vacuum. The numerical results of free-surface flow measures are compared to previous calculations and experimental values. The investigation shows that the used two-phase method is well-suited to predict the location and shape of the interface.