UC Berkeley

Flowing particulate media are ubiquitous in a wide spectrum of applications that include transport systems, fluidized beds, manufacturing and materials processing technologies, energy conversion and propulsion technologies, sprays, jets, slurry flows, and biological flows. The discrete nature of the media, along with their underlying coupled multi-physical interactions can lead to a variety of interesting phenomena, many of which are unique to such media - for example, turbulent diffusion and preferential concentration in particle laden flows, and soliton like excitation patterns in a vibrated pile of granular material. This dissertation explores the utility of numerical simulations based on the discrete element method and collision driven particle dynamics methods for analyzing flowing particulate media. Such methods are well-suited to handle phenomena involving particulate, granular, and discontinuous materials, and often provide abilities to tackle complicated physical phenomena, for which pursuing continuum based approaches might be difficult or sometimes insufficient. A detailed discussion on hierarchically representing coupled, multi-physical phenomena through simple models for underlying physical interactions is presented. Appropriate physical models for mechanical contact, conductive and convective heat exchange, fluid-particle interactions, adhesive and near-field effects, and interaction with applied electromagnetic fields are presented. Algorithmic details on assembling the interaction models into a large-scale simulation framework have been elaborated with illustrations. The assembled frameworks were used to develop a computer simulation library (named `Software Library for Discrete Element Simulations' (SLIDES) for the sake of reference and continued future development efforts) and aspects of the architecture and development of this library have also been addressed. This is an object-oriented discrete particle simulation library developed in Fortran capable of performing fully 3D simulations of particulate systems. The utility and effectiveness of the developed simulation frameworks have been demonstrated using two case studies. The first study is on the analysis of the high velocity impact of stream of particles on a porous layer of material, which is a problem of interest in the analysis of erosive wear of manufactured surface coatings. The second case-study is based on the deposition of flowing particulate spray on a target surface, which is a problem of interest in the analysis of particulate deposition-based manufacturing processes. In both cases, the aspect of extracting important information on system behavior from the collective dynamics of the particulate media has been outlined. For the first case, this involved a characterization of material damage due to impact generated stresses, and for the second case, this involved analysis of adhesion and deposited coating properties.