Unsteady Mixing Performance in Single Screw Extruders

The dimensionless control equations of three dimensional flow in single screw extruders is developed in terms of velocity and vertorcity, and then a new method for solving the Non-newtionian flow is presented without solving pressure equation. The simulation concerns the incompressible fluid obeying power law properties and the application of finite volume method to the geometrical configuration of channel derived from the single screw extruder. The deformation of the tracer is numerically integrated by the fourth order Runge-Kutta scheme. The evolutions of tracers are captured when time is forward. The tracers of the from different initial positions with different orientations reveal that growth of interfaces fall on the whole onto the linear relations accompanied by periodic osillatory effect. The closer the tracer approaches the channel walls, the more obvious the osillatory effect is. The pulse amplitude become larger and larger with time when the orientation of initial interface is along the direction of the channel height. Both have the same periods as those of the tracers which have the same midpoints with direction along the channel width. It shows that unsteady effect occurs in the mixing process during the course of the steady extrusion.