A Fluctuating Immersed Boundary Method for Brownian Suspensions of Rigid Particles*

I will describe how to model Brownian suspensions of passive or active particles and rigid bodies using an immersed boundary (IB) approach. I will first discuss minimally-resolved models in which each suspended spherical particle is represented by a single IB marker [F. Balboa Usabiaga and R. Delgado-Buscalioni and B. E. Griffith and A. Donev, Computer Methods in Applied Mechanics and Engineering, 269:139-172, 2014; and S. Delong, F. Balboa Usabiaga, R. Delgado-Buscalioni, B. E. Griffith and A. Donev, J. Chem. Phys., 140, 134110, 2014]. More complex rigid bodies suspensed in fluid can be represented with different degrees of fidelity by enforcing a rigidity constraint for each partially- or fully-resolved body [B. Kallemov, A. Bhalla, A. Donev, and B. Griffith, in preparation]. Thermal fluctuations and thus Brownian motion can be consistently modeled by including a fluctuating (random) stress in the momentum equation, as dictated by fluctuating hydrodynamics.