A discrete element analysis of cohesive granular bulk solid materials

In bulk handling applications, such as conveying and storage, understanding the effect cohesion has upon the flow-ability of particulate systems at the macroscopic scale is crucial in increasing the avenues of operation unit design improvements and handling scenarios of industrial operational units. This research provides a better understanding of the role cohesion has on the flow-ability of bulk solids materials through the development, implementation and application of a macroscopic elasto-plastic adhesive (MEPA) contact model within an open source HPC general purpose Discrete Element Method (DEM) computer code. This investigation proposed a DEM history dependent particle-particle MEPA contact model that accounts for both elastic and plastic contact deformations and adhesive attractions. The research tasks are focused in three major areas: 1) DEM applications for the analysis of cohesive bulk solids, 2) modeling stress history ependency of cohesive strength, and 3) the prediction of flow properties in test applications that are comparable to experimental results. The MEPA model applied herein is a three branched non-linear contact model that simulates the virgin compaction loading, unloading/reloading and adhesion behavior of a part iculate solid

A review of recent work on the discrete particle method at the University of Twente: an introduction to the open-source package MercuryDPM

In this paper we review some recent advances in DEM (DPM) modelling undertaken at the University of Twente. We introduce the new open-source package MercuryDPM that we have been developing over the last few years.\ud MercuryDPM is an object-oriented program with a simple C++ implementation and includes: support for moving and complex walls, such as polyhedra or screw-threads; state-of-the-art granular contact models; multi-species support; specialised classes, allowing the easy implementation of common geometries like chutes, hoppers, etc.; common handler interfaces for particles, walls and boundaries (so all type of objects are changed using the same interfaces); restarting; large self-test suite and numerous simple demos; and, visualisation support, both internal and using Visual Molecular Dynamics.\ud Additionally to these features, MercuryDPM has two major components that, to the best of our knowledge, cannot be found in other DPM packages. Firstly, it uses a novel advanced contact detection method that is able of dealing with multiple distinct granular components with sizes ranging over many orders of magnitude: the hierarchical grid. We explain how this algorithm works and demonstrate the speedup gained over the traditional linked cell approach. This algorithm has lower complexity for poly-dispersed ows which means for the first time large simulations with extremely wide size distributions are feasible.\ud Secondly, we present a novel way to extract continuum fields from discrete particle systems that is applicable to mixtures as well as boundaries and interfaces. The particle data is coarse grained in a way that is by construction compatible with the continuum equations of mass-, momentum-, and energy balance. Boundary interaction forces are taken into account in a self-consistent way and thus allow the construction of a continuous stress field even within one particle radius of the boundaries. The method does not require temporal averaging and thus can be used to investigate time-dependent flows as well as static and steady situations. This coarse-graining method is available from MercuryDPM either as a post-processing tool or it can be run in real time. In real-time mode, it not only reduces the data which has to be stored but also allows boundary conditions etc. to be updated depending on the current macroscopic state of the system, e.g. allowing the creation of a pressure-release wall.\ud Finally, we illustrate these tools and a selection of other features of MercuryDPM via various problems including size-driven segregation in chute flow, rotating drums, and screw-conveyer

Calcite-Mineralized Fossil Wood from Vancouver Island, British Columbia, Canada

Calcite-mineralized wood occurs in marine sedimentary rocks on Vancouver Island, British Columbia at sites that range in age from Early Cretaceous to Paleocene. These fossil woods commonly have excellent anatomical preservation that resulted from a permineralization process where calcite infiltrated buried wood under relatively gentle geochemical conditions. Wood specimens typically occur in calcareous concretions in feldspathic clastic sediment. Other concretions in the same outcrops that contain abundant mollusk and crustacea fossils are evidence that plant remains were fluvially transported into a marine basin. Fossiliferous concretions commonly show zoning, comprising an inner region of progressive precipitation where calcite cement developed as a concentric halo around the organic nucleus. An outer zone was produced by pervasive cementation, which was produced when calcite was simultaneously precipitated in pore spaces over the entire zone

7th International Conference on Discrete Element Methods

This book presents the latest advances in Discrete Element Methods (DEM) and technology. It is the proceeding of 7th International Conference on DEM which was held at Dalian University of Technology on August 1 - 4, 2016. The subject of this book are the DEM and related computational techniques such as DDA, FEM/DEM, molecular dynamics, SPH, Meshless methods, etc., which are the main computational methods for modeling discontinua. In comparison to continua which have been already studied for a long time, the research of discontinua is relatively new, but increases dramatically in recent years and has already become an important field. This book will benefit researchers and scientists from the academic fields of physics, engineering and applied mathematics, as well as from industry and national laboratories who are interested in the DEM.

A discrete element analysis of cohesive granular bulk solid materials

In bulk handling applications, such as conveying and storage, understanding the effect cohesion has upon the flow-ability of particulate systems at the macroscopic scale is crucial in increasing the avenues of operation unit design improvements and handling scenarios of industrial operational units. This research provides a better understanding of the role cohesion has on the flow-ability of bulk solids materials through the development, implementation and application of a macroscopic elasto-plastic adhesive (MEPA) contact model within an open source HPC general purpose Discrete Element Method (DEM) computer code. This investigation proposed a DEM history dependent particle-particle MEPA contact model that accounts for both elastic and plastic contact deformations and adhesive attractions. The research tasks are focused in three major areas: 1) DEM applications for the analysis of cohesive bulk solids, 2) modeling stress history ependency of cohesive strength, and 3) the prediction of flow properties in test applications that are comparable to experimental results. The MEPA model applied herein is a three branched non-linear contact model that simulates the virgin compaction loading, unloading/reloading and adhesion behavior of a part iculate solid

MercuryDPM: A fast and flexible particle solver part a: Technical advances

MercuryDPM is an open-source particle simulation tool—fully written in C++—developed at the University of Twente. It contains a large range of contact models, allowing for simulations of complex interactions such as sintering, breaking, plastic deformation, wet-materials and cohesion, all of which have important industrial applications. The code also contains novel complex wall generation techniques, that can exactly model real industrial geometries. Additionally, MercuryDPMs’ state-of-the-art built-in statistics package constructs accurate three-dimensional continuum fields such as density, velocity, structure and stress tensors, providing information often not available from scaled-down model experiments or pilot plants. The statistics package was initially developed to analyse granular mixtures flowing over inclined channels, and has since been extended to investigate several other granular applications. In this proceeding, we review these novel techniques, whereas its applications will be discussed in its sequel