| Abstract: | The present paper considers the problem of predicting extrudate shapes from asymmetrical dies for Newtonian and non-Newtonian fluids. The flow is fully three-dimensional and an exploration of finite elements and boundary elements is made with a view to finding accurate, stable and economical schemes. A number of finite elements are compared and we conclude that some of the Fortin elements are most useful on the grounds of computational overhead and solution accuracy. These have been used to investigate some symmetrical (square dies) and asymmetrical (unequal lip) planar and general L-shaped die flows for Newtonian fluids. The question of predicting regions of plug flow is addressed for materials with a yield stress in the three-dimensional case. Finally, we show that an unconstrained extrudate may, in absence of gravity, describe a helix in space as the most general result. |
