Restructuring of colloidal aggregates in shear flows and limitations of the free-draining approximation.
We investigated the restructuring behavior of colloidal aggregates by means of the discrete element method. We used a recently proposed model [V. Becker, H. Briesen, Physical Review E 78 (6) (2008) 061404] for tangential inter-particle forces, capable of supporting bending moments. We extended this model by the capability of supporting torsional moments. The time evolution of the aggregates' radius of gyration was tracked and a power law relation between the number of primary particles and the final radius of gyration was found. For the hydrodynamic drag forces the free-draining approximation is employed. We investigated the quality of the free-draining approximation by fully resolved finite element simulations for small aggregates. We found that the free-draining approximation overestimates the drag forces and we identified the usage of effective shear rates as a possible ansatz for reduced modeling of hydrodynamic forces.
Becker
Volker
V
Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstrasse 1, D-39108 Magdeburg, Germany. becker@mpi-magdeburg.mpg.de
Schlauch
Eva
E
Behr
Marek
M
Briesen
Heiko
H