H067-03
Mesh-Free numerical simulation of swarm transport and evolution in fractured media

Wednesday, 9 December 2020: 07:08
Virtual
Ludwig Nitsche, University of the District of Columbia, Mechanical Engineering, Washington, DC, United States, Chven A Mitchell, Purdue University, Earth, Atmospheric and Planetary sciences, West Lafayette, IN, United States and Laura J Pyrak-Nolte, Purdue University, Department of Physics and Astronomy; Department of Earth, Atomospheric and Planetary Sciences; Lyles School of Civil Engineering, West Lafayette, IN, United States; Purdue University, Lyles School of Civil Engineering, West Lafayette, IN, United States
Recorded Presentation
Abstract:
The fundamental physics and collective hydrodynamics of particulate swarms in fractured media is important in applications that seek to either maximize micro-particulate transport or mitigate the spread of pollutants in the subsurface. In geologic or engineered systems, swarms may form when colloids become localized and migrate together while settling under gravity. We consider low-Reynolds-number particle-particle and particle-wall hydrodynamic interactions in the movement and shape evolution of a swarm of particles within confined or partially confined fracture geometries.

Numerical simulations track a swarm of particles that mutually interact through their (inertia-less) Stokeslets fields while settling under gravity. An accelerated summation scheme drastically reduces computation below O(N2) operations. Wall effects in various fracture geometries are modeled using the method of fundamental solutions (MFS). To support quantitative comparison of the results with previous experiments, the initial injection process is also modeled with suitable wall effects, and experimental parameters of the swarm and fractures are incorporated into the simulations.

The simulations demonstrate that the fundamental phenomena observed during experiments (tail formation, breakup, and bifurcation of a swarm) can be explained within the realm of Stokes flow. Results also reveal how strongly the ultimate breakup depends upon the early swarm shape, which is affected by details of the injection process and wall effects. Breakup of the swarm reduces its settling speed, so time/distance to breakup is an important quantity for the efficiency of transport of subsurface particulates. Directions of future research will be discussed, including multi-scale porous spaces and polydisperse swarms.

Acknowledgment: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Geosciences Research Program under Award Number (DE-FG02-09ER16022).

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