Dynamics of Complex Fluids
A complex fluid consists of (a large number of) similar mobile entities which are complex enough by themselves to preclude a straightforward prediction of the collective behaviour of the whole. Our research aims at understanding phenomena of self-organization, such as pattern formation and self-assembly, in complex fluids. We hope to identify suitable model systems which yield insight into overarching principles of self-organization in systems as diverse as granular flows, pattern formation in geological settings, aggregation of planetesimals in primordial clouds, swarming in bacterial colonies or in plancton, or patterns in traffic flow. One challenging question is: are there general common ‘principles’ behind the various instance of symmetry breaking, structure formation, and emergence in open systems? Either finding such principles or proving their non-existence would be equally rewarding. Aside from spontaneous symmetry breaking mechanisms, an important branch of study with great application potential are systems with quenched disorder, such as wetting of random structures. We employ a wide scope of methods, including analytical statistical theory, advanced simulation tools, and cutting edge experimental techniques.
On the fundamental side, granular materials (both dry and wet) have proved to be versatile model systems for studying collective behavior in systems violating detailed balance on the microscopic level. Their particular charm lies in their position at the border of complex interfaces, soft matter, and systems far from thermal equilibrium, thereby connecting fields of expertise of different subgroups of the department. This becomes particularly obvious in our projects investigating the pore-scale physics of oil recovery (funded by BP Inc.), which combines granular physics and wetting with quenched disorder. On the complex side, biological matter and bio-systems are the most intricate systems we are studying, but we try to concentrate on those which are still simple enough to be described by physical and physico-chemical principles. By combination with our expertise in granular systems, a naturally emerging focus of our research is on life in complex geometries. A project with particularly close connection to everyday life concerns public transportation, where we try to establish a demand-driven system in Southern Lower Saxony, on the basis of first-principles statistical physics and state-of-the-art numerical simulations.