A master curve for the onset of shear induced restructuring of fractal colloidal aggregates

Colloidal aggregates exposed to shear flow exhibit a size-dependent qualitative behavior [Becker et al. JCIS, 339, 362–372, 2009]. Under the same flow conditions small aggregates rotate like rigid bodies, whereas larger aggregates change their structure and even bigger aggregates break. In this study the transition from the rotational regime to the restructuring regime is investigated by DEM simulations. We applied a model for tangential interaction, capable of supporting bond-bending moments and torsional torques [Becker, Briesen, Phys. Rev. E, 78, 2008, 061404]. The probability for an aggregate to be affected by restructuring changes with the number of primary particle from zero to one in a small interval. The probability becomes a master curve being independent of the shear flow and the interparticle interactions if it is represented as a function of the relative deviation from the critical particles number, i.e. the number of primary particle where the probability of restructuring is equal to 0.5. Investigating the dependency of the critical particle number on the shear rates reveals power law relations which adequately represents the data. The exponents in the power law relations can particularly obtained from a fractal scaling argument.

The onset of restructuring of colloidal aggregates is investigated by means of DEM simulation. The probability r q for an aggregate to be affected from restructuring can be represented by a master curve. The dependency of the critical particle number on the tangential/torsional resistance shear rates ratios Π1,Π2Π1,Π2 reveals a power law relation.Figure optionsDownload high-quality image (139 K)Download as PowerPoint slide