article

Abstract

Slip at the wall is often encountered during the flow of polymeric fluids and suspensions in processing equipment. A numerical model is developed in this article to simulate the flow of a Generalised Newtonian and a Bingham fluid, where the slip velocity at the wall is related linearly to the shear stresses. A novel method based on a penalty parameter is developed to implement the slip boundary condition into the Finite Element Method, which results in more stable solutions. The flow in the conveying elements of the extruder is used as an example of the application of the method. It is shown that slip reduces the pressurisation capability of the extruder and its mixing efficiency. The technique developed in this article can be applied to many flows and be used to gain better understanding of the dynamics of polymer mixing.

Int. Polymer Processing, 7, 132-139, 1992

Numerical study of slip at the walls in the extruder