When a viscous fluid is extruded from a capillary or an annular die, the thickness of the fluid jet is in general unequal to the width of the die. This phenomenon is called “die-swell” and is studied in this paper for a die made up of two parallel plates. It is assumed that no slip will occur between the fluid and the plates, and that the pressure in the space into which the fluid is emitted is constant and uniform. The fluid surface is a free streamline. Its shape is calculated with the use of complex-function theory and conformal-mapping techniques. The predicted ratio of swell is found to be in full agreement with known finite-element results.

/pdf/the-free-boundary-problem-for-the-die-swell-of-a-viscous-2vay3lmma8.pdf

A.J.M. Sipers

Papers

The free-boundary problem for the die-swell of a viscous fluid