A discrete element method (DEM), also called a distinct element method, is any of a family of numerical methods for computing the motion and effect of a large number of small particles. Though DEM is very closely related to molecular dynamics, the method is generally distinguished by its inclusion of rotational degrees-of-freedom as well as stateful contact and often complicated geometries. With advances in computing power and numerical algorithms for nearest neighbor sorting, it has become possible to numerically simulate millions of particles on a single processor. Today DEM is becoming widely accepted as an effective method of addressing engineering problems in granular and discontinuous materials, especially in granular flows, powder mechanics, and rock mechanics. DEM has been extended into the Extended Discrete Element Method taking heat transfer, chemical reaction and coupling to CFD and FEM into account.
Olgierd Cecil Zienkiewicz was a British academic of Polish descent, mathematician, and civil engineer. He was born in Caterham, England. He was one of the early pioneers of the finite element method. Since his first paper in 1947 dealing with numerical approximation to the stress analysis of dams, he published nearly 600 papers and wrote or edited more than 25 books.
Discontinuous deformation analysis (DDA) is a type of discrete element method (DEM) originally proposed by Shi in 1988. DDA is somewhat similar to the finite element method for solving stress-displacement problems, but accounts for the interaction of independent particles (blocks) along discontinuities in fractured and jointed rock masses. DDA is typically formulated as a work-energy method, and can be derived using the principle of minimum potential energy or by using Hamilton's principle. Once the equations of motion are discretized, a step-wise linear time marching scheme in the Newmark family is used for the solution of the equations of motion. The relation between adjacent blocks is governed by equations of contact interpenetration and accounts for friction. DDA adopts a stepwise approach to solve for the large displacements that accompany discontinuous movements between blocks. The blocks are said to be "simply deformable". Since the method accounts for the inertial forces of the blocks' mass, it can be used to solve the full dynamic problem of block motion.
The material point method (MPM) is a numerical technique used to simulate the behavior of solids, liquids, gases, and any other continuum material. Especially, it is a robust spatial discretization method for simulating multi-phase (solid-fluid-gas) interactions. In the MPM, a continuum body is described by a number of small Lagrangian elements referred to as 'material points'. These material points are surrounded by a background mesh/grid that is used only to calculate gradient terms such as the deformation gradient. Unlike other mesh-based methods like the finite element method, finite volume method or finite difference method, the MPM is not a mesh based method and is instead categorized as a meshless/meshfree or continuum-based particle method, examples of which are smoothed particle hydrodynamics and peridynamics. Despite the presence of a background mesh, the MPM does not encounter the drawbacks of mesh-based methods which makes it a promising and powerful tool in computational mechanics.
A CFD-DEM model is suitable for the modeling or simulation of fluid-solids or fluid-particles systems. In a typical CFD-DEM model, the phase motion of discrete solids or particles is obtained by the Discrete Element Method (DEM) which applies Newton's laws of motion to every particle and the flow of continuum fluid is described by the local averaged Navier–Stokes equations that can be solved by the traditional Computational Fluid Dynamics (CFD). The model is first proposed by Tsuji et al. The interactions between the fluid phase and solids phase is better modeled according to Newton's third law.
Peter Rolfe Vaughan ACGI, DIC, FREng, FICE, FCGI, MASCE, FGS, was Emeritus Professor of Ground Engineering in the Geotechnics department of Imperial College London.
Compaction simulation is the modelling of granular matter when compressed into a dense state that is achieved through the reduction of the air void. The term is also commonly used to mean compaction using a compaction simulator. This is a high performance programmable servo-controlled press for simulating production presses, typically in the pharmaceutical, catalyst, battery and magnet industries.
Slope stability analysis is a static or dynamic, analytical or empirical method to evaluate the stability of earth and rock-fill dams, embankments, excavated slopes, and natural slopes in soil and rock. Slope stability refers to the condition of inclined soil or rock slopes to withstand or undergo movement. The stability condition of slopes is a subject of study and research in soil mechanics, geotechnical engineering and engineering geology. Analyses are generally aimed at understanding the causes of an occurred slope failure, or the factors that can potentially trigger a slope movement, resulting in a landslide, as well as at preventing the initiation of such movement, slowing it down or arresting it through mitigation countermeasures.
The Rankine lecture is an annual lecture organised by the British Geotechnical Association named after William John Macquorn Rankine, an early contributor to the theory of soil mechanics.
Alan Wilfred Bishop was a British geotechnical engineer and academic, working at Imperial College London.
Sarada Kanta Sarma is a geotechnical engineer, emeritus reader of engineering seismology and senior research investigator at Imperial College London. He has developed a method of seismic slope stability analysis which is named after him, the Sarma method.
Modelling of particle breakage is a process used in grinding.
The Newmark's sliding block analysis method is an engineering that calculates permanent displacements of soil slopes during seismic loading. Newmark analysis does not calculate actual displacement, but rather is an index value that can be used to provide an indication of the structures likelihood of failure during a seismic event. It is also simply called Newmark's analysis or Sliding block method of slope stability analysis.
The Sarma method is a method used primarily to assess the stability of soil slopes under seismic conditions. Using appropriate assumptions the method can also be employed for static slope stability analysis. It was proposed by Sarada K. Sarma in the early 1970s as an improvement over the other conventional methods of analysis which had adopted numerous simplifying assumptions.
The extended discrete element method (XDEM) is a numerical technique that extends the dynamics of granular material or particles as described through the classical discrete element method (DEM) by additional properties such as the thermodynamic state, stress/strain or electro-magnetic field for each particle. Contrary to a continuum mechanics concept, the XDEM aims at resolving the particulate phase with its various processes attached to the particles. While the discrete element method predicts position and orientation in space and time for each particle, the extended discrete element method additionally estimates properties such as internal temperature and/or species distribution or mechanical impact with structures.
David Malcolm Potts is a professor of Analytical Soil Mechanics at Imperial College London and the head of the Geotechnics Section at Imperial College. He has been a member of the academic staff at Imperial College since 1979, responsible for teaching the use of analytical methods in geomechanics and the design of slopes and earth retaining structures, both at undergraduate and postgraduate levels.
Charles Peter Wroth (1929–1991) was a British Civil Engineer, a world pioneer in Geotechnical Engineering and Soil Mechanics. He led the design and construction of the Hammersmith flyover.
Nicholas Neocles Ambraseys FICE FREng was a Greek engineering seismologist. He was emeritus professor of Engineering Seismology and Senior Research Fellow at Imperial College London. For many years Ambraseys was considered as the leading figure and an authority in earthquake engineering and seismology in Europe.
David William Hight is a Senior Consultant at the Geotechnical Consulting Group, a company providing high-level expertise in the field of geotechnical engineering and well known for bridging the gap between research and engineering practice.
In geology, numerical modeling is a widely applied technique to tackle complex geological problems by computational simulation of geological scenarios.
