Simulations of Particle Dynamics in Stokes Flow: Polydispersity and Flexibility

2D materials are promising high-performance sheet-like nanomaterials with unique properties. Liquid-phase exfoliation (LPE) is a scalable and cost-effective process to produce 2D materials on large scales. However, the product of LPE is highly polydispersed. An efficient procedure to fractionate 2D materials is the liquid cascade centrifugation (LCC), which is currently done by trial and error. Moreover, 2D materials are easily deformed when processed in liquids because of their low bending rigidities. To exploit the unique properties of 2D materials, it is essential to control the sizes and morphologies of the nanosheets.
To provide insights for the rational design of the LCC procedure and the understanding of deformation of nanosheets in the shear flow, this thesis tackles two relevant fluid dynamics problems: (i) sedimentation of polydisperse suspensions, and (ii) buckling of flexible particles in the shear flow, both in the Stokes flow regime. The approaches adopted in this thesis are mainly numerical, including Stokesian dynamics and boundary integral method, which are efficient methods to simulate particle dynamics in Stokes flow. Moreover, collaborations with experimentalists have been established during this thesis. The code developed has been used to answer practical questions.
Overall, this thesis contributes to the understanding of particle dynamics in Stokes flow, including the settling of polydisperse suspensions and buckling of flexible sheets in the shear flow, utilizing the theories and numerical approaches of microhydrodynamics. Results of this thesis can be used to optimize the procedures of liquid processing of 2D nanomaterials and in other relevant applications.