Velocity distributions in die swell

Photographs of tracer particles were used to measure axial and transverse velocity components throughout the entire die swell region in a slit die. Laminar extrusion was investigated for two fluids: a viscoelastic concentrated solution of a polyacrylamide in glycerin and water and a highly viscous, nearly Newtonian, silicone oil. The die swell region extends upstream to the viscometric flow region and downstream to the relaxed portion of the extrudate. The data are used to evaluate several theories of die swell.