Berlin 2015 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 61: Focus: Disordered Systems, Glasses under Shear I (joint session CPP, DY)
CPP 61.7: Vortrag
Donnerstag, 19. März 2015, 11:45–12:00, C 243
Lattice Boltzmann Simulations of Glass Forming Liquids — •Simon Papenkort1 and Thomas Voigtmann1,2 — 1Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Köln — 2Heinrich-Heine-Universität Düsseldorf
The rheology of complex fluids undergoing a glass transition, such as colloidal suspensions or granular media, is highly nonlinear. The interplay between slow structural dynamics on the microscopic scale and a mesoscopic flow field gives rise to non-Newtonian flow effects. Prominent examples are shear thinning, dynamic yield and residual stresses. In a confined flow geometry, the shear rates, and thereby the fluid properties, can vary considerably in space and time. Even long after the flow has stopped, the material properties are profoundly affected by residual stresses.
Starting from first principles, mode coupling theory of the glass transition is able to provide constitutive equations that describe the history effects determining the flow of glass-forming fluids. The Lattice Boltzmann method is a modern simulation scheme to solve the Navier-Stokes equations even for complex flow geometries. We introduce a new, modified LB model [1] which is able to include memory-integral effects in fluid-mechanics simulations and provides a link between both regimes.
We find the viscoelastic transient dynamics and the appearance of residual stresses after stopping the flow to depend sensitively on the chosen flow geometry.
[1] J. Chem. Phys. 140, 164507 (2014)