Discrete-element modelling: methods and applications in the environmental sciences. Philos Transact A Math Phys Eng Sci

Department of Earth Sciences, University of Cambridge, Cambridge, England, United Kingdom
Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences (Impact Factor: 2.15). 10/2004; 362(1822):1797-816. DOI: 10.1098/rsta.2004.1429
Source: PubMed


This paper introduces a Theme Issue on discrete-element modelling, based on research presented at an interdisciplinary workshop on this topic organized by the National Institute of Environmental e-Science. The purpose of the workshop, and this collection of papers, is to highlight the opportunities for environmental scientists provided by (primarily) off-lattice methods in the discrete-element family, and to draw on the experiences of research communities in which the use of these methods is more advanced. Applications of these methods may be conceived in a wide range of situations where dynamic processes involve a series of fundamental entities (particles or elements) whose interaction results in emergent macroscale structures. Indeed, the capacity of these methods to reveal emergent properties at the meso- and macroscale, that reflect microscale interactions, is a significant part of their attraction. They assist with the definition of constitutive material properties at scales beyond those at which measurement and theory have been developed, and help us to understand self-organizing behaviours. The paper discusses technical issues including the contact models required to represent collision behaviour, computational aspects of particle tracking and collision detection, and scales at which experimental data are required and choices about modelling style must be made. It then illustrates the applicability of DEM and other forms of individual-based modelling in environmental and related fields as diverse as mineralogy, geomaterials, mass movement and fluvial sediment transport processes, as well as developments in ecology, zoology and the human sciences where the relationship between individual behaviour and group dynamics can be explored using a partially similar methodological framework.

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    • "Large-scale DEM simulations have a significant potential in many areas of research and technology, including the environmental sciences to, e.g. simulate land slides or avalanches (Cleary and Prakash, 2004; Richards et al., 2004), the study of complex selforganization phenomena as, e.g. in singing sand dunes (Douady et al., 2006), and research toward answering open questions in the continuum modeling of granular matter (de Gennes, 1999). "
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    ABSTRACT: Purpose - The purpose of this paper is to present large-scale parallel direct numerical simulations of granular flow, using a novel, portable software program for discrete element method (DEM) simulations. Design/methodology/ approach - Since particle methods provide a unifying framework for both discrete and continuous systems, the program is based on the parallel particle mesh (PPM) library, which has already been demonstrated to provide transparent parallelization and state-of-the-art parallel efficiency using particle methods for continuous systems. Findings - By adapting PPM to discrete systems, results are reported from three-dimensional simulations of a sand avalanche down an inclined plane. Originality/value - The paper demonstrates the parallel performance and scalability of the new simulation program using up to 122 million particles on 192 processors, employing adaptive domain decomposition and load balancing techniques.
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    • "In recent years individual-based and multi-agent (Gilbert, 2007; Wooldridge, 2001) approaches to land-use change modelling have begun to be adopted, as they allow a more flexible approach to the representation of people's interaction with the environment: spatial heterogeneity can be more easily included, and the effects of decision making disaggregated (Barthel et al., 2008; Monticino et al., 2007; Matthews et al., 2007; Richards et al., 2004a,b; Parker et al., 2003). The potential for using agent models in ecosystem management has been described by Doran (2001) and has also been reviewed more recently by Bousquet and Le Page (2003). "
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    ABSTRACT: Subsistence farming communities are dependent on the landscape to provide the resource base upon which their societies can be built. A key component of this is the role of climate and the feedback between rainfall, crop growth, land clearance and their coupling to the hydrological cycle. Temporal fluctuations in rainfall alter the spatial distribution of water availability, which in turn is mediated by soil-type, slope and landcover. This pattern ultimately determines the locations within the landscape that can support agriculture and controls sustainability of farming practices. The representation of such a system requires us to couple together the dynamics of human and ecological systems and landscape change, each of which constitutes a significant modelling challenge on its own. Here we present a proto-type coupled modelling system to simulate land-use change by bringing together three simple process models: (a) an agent-based model of subsistence farming; (b) an individual-based model of forest dynamics; and (c) a spatially explicit hydrological model which predicts distributed soil moisture and basin scale water fluxes. Using this modelling system we investigate how demographic changes influence deforestation and assess its impact on forest ecology, stream hydrology and changes in water availability.
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    • "The rapid development and application of DEM can also be highlighted by the large number of papers based on DEM at major international conferences, for example, from 29 in 2001 to 80 in 2005 for the International Conference on Powders and Grains, and from 34 in 2002 to 92 in 2006 for the World Congress on Particle Technology. In spite of the large bulk volume, little effort has been made to comprehensively review and summarize the progress made in the past, except for a few relatively focused reviews including, for example, Tsuji (1996) on the work in Japan, Mishra (2003a,b) on tumbling milling processes, Yu (2004) on the work done in his laboratory, Richards et al. (2004) on environmental science, and Bertrand et al. (2005) on mixing of granular materials. To overcome this gap, we have recently reviewed the major work in this area with special reference to the soft-particle model. "
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    ABSTRACT: Particle science and technology is a rapidly developing interdisciplinary research area with its core being the understanding of the relationships between micro-and macroscopic properties of particulate/granular matter—a state of matter that is widely encountered but poorly understood. The macroscopic behaviour of particulate matter is controlled by the interactions between individual particles as well as interactions with surrounding fluids. Understanding the microscopic mechanisms in terms of these interaction forces is therefore key to leading to truly interdisciplinary research into particulate matter and producing results that can be generally used. This aim can be effectively achieved via particle scale research based on detailed microdynamic information such as the forces acting on and trajectories of individual particles in a considered system. In recent years, such research has been rapidly developed worldwide, mainly as a result of the rapid development of discrete particle simulation technique and computer technology. This paper reviews the work in this area with special reference to the discrete element method and associated theoretical developments. It covers three important aspects: models for the calculation of the particle–particle and particle–fluid interaction forces, coupling of discrete element method with computational fluid dynamics to describe particle–fluid flow, and the theories for linking discrete to continuum modelling. Needs for future development are also discussed.
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