Extrudate swell of Newtonian fluids from converging and diverging annular dies

Finite element results are presented for the extrudate swell of Newtonian fluids from converging and diverging annular dies. Numerical calculations for a variety of diameter ratios and taper angles show the dependance of diameter and thickness swell on the angle. For diverging dies a thickness contraction occurs for angles greater than 30 degrees, while the diameter swell increases rapidly. For converging dies the design is limited to angles that do not allow contact of the inner free surfaces. The present results show that the diameter swell is highest for the diverging, followed by the straight and then the converging dies.