Analysis of shear-thinning fluid flow in intermeshing twin-screw extruders

The paper deals with the analysis of three-dimensional incompressible flows of generalized Newtonian liquids in corotating twin-screw equipment where the fluid-filled region is rather complex and changes in time as the screws rotate. Taking notice of the fact that the flow fields are periodic in time and, simultaneously, periodic in axial direction, a mixed finite element method is applied for the sake of discretization. The resulting systems of nonlinear algebraic equations are treated by a Newton iteration where the linear subproblems with indefinite sparse coefficient matrices are solved by applying a modified Uzawa algorithm. By simulating different working conditions, the screw characteristics are extracted numerically, and the influence of Deborah number is demonstrated. Selected flow fields are visualized grafically illustrating the intermeshing screw operation principle and demonstrating certain symmetries connected with the kinematic reversibility of nonlinear viscous creeping flows.