Inhalt des Dokuments
Project B1: Structure formation of ferrofluids driven by oscillating magnetic fields.
In this project we plan to
investigate the nonlinear dynamics of ferrofluids
under the
influence of time-dependent magnetic fields. The dipole-field
coupling drives the particles constantly away from equilibrium.
Nonlinearity
occurs through the 1/r³ dependence of the dipolar
interactions and through
the hydrodynamic interactions. We will
mainly employ computer simulation
techniques such as Molecular
Dynamics, Brownian Dynamics, and simulations
with additional
hydrodynamic interactions. As a long-term goal we further aim
to
develop an effective description using concepts of dynamic density
functional
theory. In a first step we will focus on the
microstructure in an oscillating field.
The effect of such
fields on the stability of the self-assembled chain-like
assemblies has so far been studied only experimentally. A
particularly important
quantity is the time-dependent structure
factor, which can be measured via
suitable SANS techniques. A
further focus will be to understand the impact of
rotating
fields. The latter have been shown, both experimentally and
theoretically,
to induce novel pattern formation effects such as
layering and formation of labyrinth
structures in the related
system of magnetorheological fluids. Comparing simulations
with
and without hydrodynamic interactions we will explore the effect of
the solvent on
the dynamics of the magnetic particles. Further
issues concern the magnetic response
and the possibility of
field-induced crystallization (or other phase transitions).
Project leaders: Prof.Dr. S. Klapp [1], Prof.Dr. H.
Stark [2]
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