NUMERICAL-SIMULATION OF EXTRUDATE SWELL FOR OLDROYD-B FLUIDS USING THE STREAM-TUBE ANALYSIS AND A STREAMLINE APPROXIMATION

In this paper, the stream-tube method is applied to the numerical simu lation of axisymmetric extrudate swell of Oldroyd-B fluids. The analys is permits computation of the flow by considering stream tubes separat ely, from the wall to the inside, in a mapped computational domain whe re the streamlines are parallel and straight. The present study follow s a previous paper on the swelling problem for a fluid obeying a memor y-integral equation. A simpler numerical model is proposed here, in wh ich the singularity in the vicinity of the junction point between the wall and the free surface, considered in the previous work, is not exa mined explicitly. Several values of the parameter beta of the Oldroyd- B model, from beta = 0.01 to beta = 1 (Maxwell model) are considered. The algorithm converges for a broad range of Weissenberg numbers. Resu lts are consistent with the numerical data in the literature. CPU time and storage area are reduced.