C6: Linking hydrodynamics and microscopic models of wet active matter with anisotropic particles

The goal of this project is to develop a systematic, quantitative coarse-graining approach for a class of inherently non-equilibrium systems, namely suspensions of self-propelled particles. We plan to link particle based models with effective hydrodynamic models within a multiscale framework based on sequential coupling and parameter passing. To this end, we will first combine microscopic Stokesian dynamics simulations with a mesoscopic kinetic model coupled to the macroscopic Stokes equation, and, in a second step, derive an effective hydrodynamic description in terms of particle density, polarization and nematic order parameter profiles. The multiscale scheme will be applied to systems of self-propelled rod-like magnetic colloids suspended in a fluid. This is motivated by recent experiments on magnetotactic bacteria, which have shown that the interplay of internal drive (self-propulsion, mutual interactions) and external drive (magnetic field, oxygen gradient) in these systems leads to emergent collective dynamics - propagating magnetotactic bands on length-scales L much larger than the particles size a, L/a > 100.