FINITE-ELEMENT ANALYSES OF THE EXTRUSION FLOWS OF BOGER FLUIDS WITH END-DRAWING AND GRAVITY-DRAWING

The spinning flow of Boger fluids and the gravity-drawing extrusion no w of a Newtonian as well as a Boger fluid have been simulated by using the stream-line finite element method and the technique of matching t he finite element solutions with those of one-dimensional spinning equ ations. The recoverable shear strain is proved not to be a basic param eter in characterising the spinning flow of Boger fluids. For Newtonia n fluids this technique predicts the experimental jet shape accurately . For Boger fluids, the numerical simulation agrees with the experimen tal data of spinning flow reported by Sridhar et al., but seems to giv e an insufficient swelling and over contraction of the jets when drawn by its own weight, compared with the experimental results of Trang an d Yeow. It implies that the Oldroyd-B model fitting the viscometric-fl ow data fails to describe accurately the elasticity and extensional vi scosity in the extrusion flow of Boger fluids with gravity-drawing.