Berlin 2008 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 2: DRG-DPG SYMPOSIUM Rheology II

CPP 2.8: Talk

Monday, February 25, 2008, 16:30–16:45, C 130

Transient behavior of thioxtropic flow studied by smoothed particle hydrodynamics — •Andreas Wonisch, Torsten Kraft, Michael Moseler, and Hermann Riedel — Fraunhofer Institute for Mechanics of Materials, Woehlerstr. 11, 79108 Freiburg

Many complex fluids exhibit thixotropic behavior: Under shear viscosity gradually decreases with time, followed by a gradual increase if the shearing is stopped. This time and shear rate dependent rheological behavior can be linked to the breakdown and buildup of structure in the fluid. Here, we employ smoothed particle hydrodynamics (SPH) - a meshless, particle-based Lagrangian simulation method - to study thixotropic fluid flow in three dimensions. In our model the structure of each SPH particle is characterized by a scalar structure parameter which is related to viscosity. Thixotropy is introduced by specifying a constitutive equation for the time derivative of the structure parameter. Our numerical method is verified by several simple test cases which are in close agreement with analytical solutions. We then investigate the transient behavior of thixotropic flow at low Reynolds numbers numbers for an industrial impregnation and removal process which involves both solid wall and free surface boundary conditions. It is demonstrated that different wetting conditions (characterized by the contact angle) have a profound impact on the transient flow behavior.