(440e) Investigations of Dynamics and Rheological Properties of Anisotropic Suspensions

Suspensions of particles in fluids are ubiquitous in both nature (e.g., proteins, bacteria, and viruses in biological media) and engineering fields (e.g., production of composite materials, dispersions of pigments in paint, and mixtures of emulsion polymers). While suspensions of spherical particles have been widely studied, suspensions of aspherical particles create new questions and phenomena that still need to be explained. Hydrodynamic interactions and/or other interactions are essential for investigating the non-equilibrium properties, such as the dynamics and mechanical properties. The hydrodynamic and other interactions depend on the configuration of the suspension, which makes itself formidable to calculate for an aspherical suspension because of the geometrical complexity. In this study, we decomposed aspherical particles into constitutive spheres and constrained them in rigid-body clusters, and the hydrodynamic interactions between clusters become the summation of the hydrodynamic interactions between constitutive spheres. To accelerate the computation, we implemented an accelerated Stokesian dynamics algorithm, which applies the particle-mesh-Ewald (PME) method to efficiently calculate the far-field interactions.

In this work, we observed that the rheological properties of suspensions of curved rods are enhanced compared with straight rods, as well as a positive dependence of rheological properties on curvature. This phenomenon is caused by the enhanced steric hindrance as the curvature increases. Thus, more energy is required to separate two closely interacting curved rods. The microstructures and mechanical properties can be dependent on external fields when the suspensions are susceptible. For example, the properties of magnetorheological (MR) fluids can vary significantly when they are subject to external magnetic fields. The algorithm of accelerated Stokesian dynamics is utilized and modified to calculate the magnetic interactions between particles. The dynamics and mechanical properties of MR fluids are studied to build the relations with the properties of magnetic fields.