Description
- Abstract:
- Neutrally buoyant, non-Brownian particles in a low Reynolds number pressure-driven flow display an irreversible net particle migration towards the center of the channel, resulting in a high concentration of particles at the channel centerline and a lower concentration elsewhere in the channel. This particle migration has been tied to small asperities on the particle surface breaking the reversibility of the particle trajectories in Stokes flow. In this work, we explore the irreversible migration of particles in high volume fraction suspension flows through direct numerical simulations under controlled conditions to provide additional insight into the particle dynamics in existing experimental results. The Force Coupling Method is used to simulate a number of non-homogeneous suspensions in steady and unsteady flows where the particles are either isolated in one area of the channel, allowing for discussion of how the particles migrate outside their original configurations, or where the particles have bidisperse size. We observe that the particle surface roughness, modeled by a short-range contact force, is critical in causing irreversible particle trajectories, however, the hydrodynamic forces must also be included in the model to capture the complete suspension dynamics when the suspension fills only part of the domain leaving regions of pure fluid elsewhere. It is shown that the particles form strong layers at the channel wall, which can be disrupted by small changes in the particle contact force. When the particles have bidisperse size, the large particles enrich the center of the channel, while the wall layer consists predominantly of small particles. If the particles are close in size, the rheology of the suspension and the particle volume fraction profiles match that of a monodisperse suspension. Finally, Generalized Moving Least Squares (GMLS), a high order meshless numerical method, is discussed as a next-generation numerical solver for suspension flows. GMLS allows for simulations of particles of arbitrary shape in domains that can change with time, providing greater flexibility for future work.
- Notes:
- Thesis (Ph. D.)--Brown University, 2018
Access Conditions
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- Restrictions on Use
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Citation
Howard, Amanda A.,
"Numerical Simulations to Investigate Particle Dispersion in Non-Homogeneous Suspension Flows"
(2018).
Applied Mathematics Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://doi.org/10.26300/kjs7-g605
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Applied Mathematics Theses and Dissertations
Theses and Dissertations for the Applied Mathematics department....