ISSN:
1435-1528
Schlagwort(e):
Stagnation flow
;
finite element
;
viscoelasticity
;
elongational flow
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Chemie und Pharmazie
,
Physik
Notizen:
Abstract A finite element simulation for the steady flow in a planar stagnation die was used to compute the velocity, pressure and stress fields. It is predicted that a region surrounds the stagnation point where the flow approximates a planar extension. This region is circular for the Newtonian liquid and becomes an ellipse for the Maxwell fluid. An isotropic point in the stress field is found for the Newtonian case as well as for the Maxwell fluid. Lubrication of the die wall, modeled as a finite slip, increases the size of extensional flow region by as much as 100%, while causing a migration of the isotropic stress point towards the die wall. A slight increase in the apparent planar extensional viscosity occurs before the numerical scheme fails at deformation rates well below the extensional singularity in the Maxwell model. Slip at the walls does not significantly alter the convergence behavior, which appears to be limited by effects in the entry region. In this region, at a Weissenberg number of 1.16, spatial oscillations in the pressure, deformation rate and stress develop. The stress normal to the main flow direction in the entry region is compressive for all values of the slip coefficient.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF01369975
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