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ORAL PRESENTATION
Session: 4 Complex fluid deformation and rheology: Theories and thermodynamic relationships
(scheduled: Tuesday, 10:20 )
Polymer rheology and nonlinear transient elasticity
O. Müller1, M. Liu1, H. Pleiner2, H.R. Brand3
1 Theoretical Physics, University of Tübingen, Germany
2 Max Planck Institute for Polymer Research, Mainz, Germany
3 Theoretical Physics III, University of Bayreuth, Germany
We simplify our previously derived general macroscopic equations incorporating transient elasticity by assuming incompressibility as well as linear response for the dissipation. We take into account terms up to quartic order in the elasticity (3 independent coefficients) and have in addition only two dissipative constants: the shear viscosity and the relaxation time of transient elasticity. This simple model can account for many experimentally observed rheological effects qualitatively and sometimes even quantitatively. Flow phenomena discussed include the Weissenberg effect, overshoot, relaxation spectra and elongational flows. © IWNET 2006
ORAL PRESENTATION
Session: 4 Complex fluid deformation and rheology: Theories and thermodynamic relationships
(scheduled: Tuesday, 14:25 )
2-Fluid Viscoelasticity
H. Pleiner1, J.L. Harden2
1 Max Planck Institute for Polymer Research, 55021 Mainz, Germany
2 Dept. Physics, University of Ottawa, Ottawa Ontario K1N 6N5, Canada
We combine the nonlinear hydrodynamic description of viscoelastic fluids with a general 2-fluid hydrodynamics of 2-component (mass density) and 2-momentum (velocity) systems to give a generalized hydrodynamics model for disperse polymers and colloids. This description deals with hydrodynamic equations for the two (generally conserved) mass densities, the total (conserved) momentum density and for the non-hydrodynamic, relaxing relative velocity, the thermal degree of freedom, and either the relaxing elasticity, or transient orientation dynamics. There are special problems with this 2-fluid extension of ordinary hydrodynamics, like the choice of the transport and convection velocities or the separation of the stress tensor between the two subsystems. Generally it turns out that transport and convective velocities are material dependent and can be different for the different variables or even from each other. However, there are certain restrictions and interdependencies among them due to thermodynamic requirements. In addition, the stress division problem is not independent from the transport and convective velocity problem. © IWNET 2006
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and Kleanthi for IWNET 2006