Development of Enhanced Three-Dimensional Simulation Capability for Analyzing the Migration of Colloids and Nanoparticles in Complex Flow Domains, 20-R9722Printer Friendly Version
Inclusive Dates: 07/01/07 Current
Background - Existing continuum-based colloidal transport models use empirical effective parameters to simulate various aspects of colloidal transport processes at a phenomenological level. Such models do not adequately address the hydrodynamic processes governing particle trajectories due to channel-wall roughness, lubrication forces, and wall and inertial effects. Nor do they incorporate chemical and physical processes such as particle attachment on fracture-wall surfaces due to the Brownian effect and particle migration in geometrically complex flow paths. These processes, however, significantly affect the retardation and migration paths of colloidal particles. Enhanced simulation capabilities would provide more reliable colloidal transport analyses supporting safety and performance assessments of potential geological repositories where colloid-facilitated transport of radionuclides may be important. Such capabilities are also useful for optimal design and deliveries of reactive agents via engineered particles to targeted sites in biomedical and subsurface bioremediation applications.
Approach - The project focuses on the development of a three-dimensional simulation capability to quantify the effects of physical, chemical, and hydrodynamic processes governing colloidal transport in complex flow. The simulation capability is based on the lattice-Boltzmann method. This method was chosen because of its computational efficiency and ease of handling complex flow domain geometries. The simulation capability will be used to quantify the effects of the particle sizes, shapes, release locations and rates, flow regimes, particle-wall interaction potentials, and particle and wall surface heterogeneities on particle trajectories in complex physical, chemical, and hydrodynamic flow systems. Because the proposed simulation capability will require developing and testing new features such as channel wall-particle interaction potentials based on short-term interaction forces and the Brownian effect for small-size particles, laboratory experiments at the microscale under different flow regimes will be conducted for model validation and improvement.
Accomplishments - The simulation capability was upgraded from a two-dimensional, single-particle model to a three-dimensional, multiple-particle model. A two-dimensional, single-particle version of the simulation model was successfully tested with the benchmark problems, comparing well with the previously published numerical results (in the form of particle trajectories in different flow regimes) from finite element simulations. The two-dimensional, multiple-particle version of the model has produced physically meaningful results, and further model validations are in progress. The numerical simulation tests were used to determine experimental design parameters, including the type and size of particles, tube dimensions, obstacles, and visualization tools. For computationally feasible simulations with the existing computational capabilities in validating the numerical model with the experimental data, the particle size will be on the order of 100 microns, and the width and length of the flow channel will be on the order of 1 cm and 10 cm, respectively. The particle dilution will be less than 1 percent initially to reduce particle-particle interactions.