A term used in capillary viscometry to describe the excess pressure drop in the entrance to the capillary due to extensional (elongational) viscosity. It might be negligible when very long capillaries [..]

During capillary rheometer tests, pressure is measured above the die inlet. The true pressure drop along the capillary is therefore ‘hidden’ by an additional pressure drop at the entrance of the die, where the flowing material goes from a wide reservoir (the main cylinder or barrel) to a narrow capillary, possibly also creating turbulences. Assumin [..]