Abstract
A combined numerical/exptl. method is described that is used for evaluation of viscoelastic constitutive equations. The method is applied to a three dimensional stagnation flow which exhibits strong elongational deformations. The material investigated is a polymer soln. (2.5% PIB/C14). Laser Doppler Anemometry and flow induced birefringence are used to measure resp. pointwise velocities and linewise (in the depth of the flow cell) stresses. Since numerical simulations of 3D viscoelastic flows are to massive yet, the deformation history of a fluid element is calcd. with the viscous Carreau Yasuda model and this history is used to calc. the stresses with the viscoelastic Giesekus and PTT model. The optical birefringence signal is calcd. from the integrated stresses, using the small retardance approxn. The approach is first tested for a slit flow (pure shear). For both models, numerical results agree well with measurements. For the stagnation flow, stresses along streamlines near the inflow and outflow symmetry plane are calcd. Using the parameters detd. in simple shear flow, both viscoelastic models predict much too low integrated normal stresses in the vicinity of the outflow centerline when compared with measured values. It is demonstrated that with a proposed new constitutive model both, viscometric data and the strong elongational flow characteristics can be described at the same time
| Original language | English |
|---|---|
| Title of host publication | Material Identification Using Mixed Numerical Experimental Methods, Proceedings of the EUROMECH Colloquium, Kerkrade, Neth., Apr. 7-9, 1997 |
| Editors | H. Sol, C.W.J. Oomens |
| Place of Publication | Dordrecht |
| Publisher | Kluwer |
| Pages | 123-132 |
| ISBN (Print) | 0-7923-4779-X |
| Publication status | Published - 1997 |