Simulations of interface driven phenomena in fluid dynamics
Complex fluids with non-Newtonian rheology are present in many products such as e.g. food and cosmetics, paints and inks, or even biological fluids such as human blood. Applications range from the general chemical industry and high-tech products such as printable electronics or photovoltaics to medical applications such as advanced drug delivery. Interfaces between different fluids or fluids and solids dominate the behavior of such complex fluids. Examples include colloidal particles or biological cells suspended in a solvent, emulsions, or fluid mixtures in confining geometries such as lab-on-a-chip devices. At the Helmholtz Institute Erlangen-Nürnberg, we aim at a fundamental understanding of such systems by means of computer simulations and in this presentation, I will focus on two examples from our recent research:
Colloidal particles adsorb to fluid-fluid interfaces and reduce the interfacial free energy which leads to an efficient interface stabilization. This effect is well known since the pioneering work of Pickering and Ramsden more than a century ago, but only recently scientists started to utilize tunable capillary interactions between adsorbed colloids to self-assemble complex structures for new soft and adaptive materials. We investigate the interplay of particle shape, contact angle, particle surface structure and external fields on the capillary assembly by means of hybrid lattice Boltzmann / molecular dynamics simulations and simple estimates of the minimum free energy of the system. We demonstrate how anisotropy in the geometry
and wettability of colloidal particles can be utilized for the direct assembly of well-defined structures.
The second part of the presentation summarizes recent results on electrokinetic effects in multiphase flows and colloidal suspensions. We coupled our lattice Boltzmann solver to a solver for the Nernst-Planck equation. This allows us to resolve the coupled dynamics of several fluid and ion species. I will present applications of this new method ranging from floating droplets deforming in electric fields to electrowetting and the formation of ordered
nanostructures in fluid mixtures with antagonistic salts.
Sprecher: Prof. Dr. Jens Harting, Helmholtz-Institut Erlangen-Nürnberg
Kontakt: Prof. Klaus Mecke