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See detailDie Extended Discrete Element Method (XDEM) als integraler Ansatz für reagierende Mehrphasenströmungen
Peters, Bernhard UL; Amir, Mahmoudi

in 26. Deutscher Flammentag Verbrennung und Feuerung (2013, September)

Eine Großzahl technischer Anwendungen wie beispielsweise in der pharmazeutischen Industrie, Nahrungsmittelindustrie, Bergbau, Verfahrenstechnik oder Energiegewinnung durch Verbrennung von Feststoffen ... [more ▼]

Eine Großzahl technischer Anwendungen wie beispielsweise in der pharmazeutischen Industrie, Nahrungsmittelindustrie, Bergbau, Verfahrenstechnik oder Energiegewinnung durch Verbrennung von Feststoffen enthalten neben einer gasförmigen oder fluiden Phase eine diskrete Phase in Form von Partikeln oder Feststoffen. Diese Anwendungen lassen sich sehr vorteilhaft mit dem innovativen Konzept der Extended Discrete Element Method (XDEM) numerisch beschreiben. Hierbei werden die einzelnen Partikel über den dynamischen Zustand (Position und Orientierung) und den thermodynamischen Zustand (Temperatur und Spezies) diskret beschrieben, wo hingegen die Gas- oder Flüssigphase über kontinuumsmechanische Ansätze der Computational Fluid Dynamics (CFD) berechnet wird. Beide Phasen – diskret und kontinuumsmechanisch – sind durch Austausch von Stoff, Wärme und Impuls gekoppelt, was damit eine detaillierte Auflösung der Phasen für CFD-Gesamtrechnungen ermöglicht. Dieser Ansatz wurde angewendet, um den Reaktionsprozess während der Pyrolyse von Holz in einem Festbettreaktor zu berechnen. [less ▲]

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See detail3D DEM – FEM Coupling to Analyse the Tractive Performance of Different Tire Treads in Soil
Michael, Mark UL; Peters, Bernhard UL

in Idelsohn, S; Papadrakakis, M; Schrefler, B (Eds.) Computational Methods for Coupled Problems in Science and Engineering V (2013, June)

This contribution investigates the tractive performance of different tire treads on granular terrain by an efficient combination of the Discrete Element Method (DEM) and the Finite Element Method (FEM ... [more ▼]

This contribution investigates the tractive performance of different tire treads on granular terrain by an efficient combination of the Discrete Element Method (DEM) and the Finite Element Method (FEM). The proposed coupling method has been shown to be a sufficient technique when resolving the different length scales involved in engineering problems dealing with granular assemblies in contact with deformable bodies [1][2]. Herein, the extended discrete element method (XDEM) is used to describe the dynamics of the granular assembly. Thereby the discrete approach accounts for the motion and forces of each grain individually. On the other hand, the finite element method accurately predicts the deformations and stresses acting within the tire tread. Hence, the simulation domain occupied by the tire is efficiently described as a continuous entity. The coupling of both method is based on the interface shared by the two spatially separated domains. The interface coupling enables to apply a contact model fitting the particular contact behaviour between the grains and the tread surface. Thus, contact forces develop at the interface and propagate into each domain. The coupling method enables to capture both responses simultaneously. Each grain in contact with the tread surface generates a contact force which it reacts on repulsively. The contact forces sum up over the surface and cause the tire tread to deform. The resultant stresses are then again recognised by the granular assembly. The coupling method compensates quite naturally the shortages of both numerical methods. It further employs a fast contact detection algorithm to spare valuable computation time [1]. The proposed DEM-FEM Coupling technique was employed to study the tractive performance of four different tire treads on a soil layer of the material sand. The simulations were conducted in accordance to the experimental measurements undertaken by Shinone et al. [3]. The contact forces at the surface of smooth, lug, rib and block tread patterns are captured by 3D simulations of different slip values of each tire tread. The simulation results are used to analyse the gross tractive effort, running resistance and drawbar pull of the different tread patterns in sand. [less ▲]

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See detailROS-induced regulation of mitophagy and its failure in Parkinson’s disease
Kolodkin, Alexey UL; Ignatenko, Andrew UL; Simeonidis, Vangelis UL et al

Poster (2013, May)

Reactive Oxygen Species (ROS) generation is an unavoidable background process in the normal functioning of the cell. The greatest contributor to ROS production is the electron transport chain (ETC) where ... [more ▼]

Reactive Oxygen Species (ROS) generation is an unavoidable background process in the normal functioning of the cell. The greatest contributor to ROS production is the electron transport chain (ETC) where O2 is reduced to H2O. Some incompletely-reduced oxygen species escape and oxidize a variety of organic molecules (e.g. proteins and lipids in the mitochondrial membrane), leading to molecular dysfunction and initiating a positive feedback loop leading to generation of even more active radicals. Increased ROS concentration damages mitochondria and further increases ROS generation. Healthy cells manage ROS enzymatically with superoxide dismutase and other enzymes, various antioxidants, and ultimately through increased mitophagy of damaged mitochondria. The precise tuning of the latter mechanism is crucial for cell survival and is controlled in the cell by a ROS-induced regulatory network, which consists of many components such as Nrf2, Keap1, Parkin and p62 with a rather complicated cross-talk (Figure 1). In many diseases (cancer, Parkinson’s disease (PD), Huntington’s disease (HD), etc.), various components of the ROS management network are altered. Deconstructing the molecular mechanisms underlying or resulting from these alterations might contribute to better understanding of the dynamics of related pathophysiological processes. We have built a kinetics-based model which recapitulates the consensus understanding of the mechanism responsible for cellular ROS – managing system. [less ▲]

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See detailThe extended discrete element method (XDEM) for multi-physics applications
Peters, Bernhard UL

in Scholarly Journal of Engineering Research (2013), 2

The Extended Discrete Element Method (XDEM) is a novel numerical simulation technique that extends the dynamics of granular materials or particles as described through the classical Discrete Element ... [more ▼]

The Extended Discrete Element Method (XDEM) is a novel numerical simulation technique that extends the dynamics of granular materials or particles as described through the classical Discrete Element Method (DEM) by additional properties such as the thermodynamic state, stress/strain, or electromagnetic field for each particle coupled to a continuum phase such as fluid flow or solid structures. Contrary to a continuum mechanics concept, XDEM aims at resolving the particulate phase through the various processes attached to particles, while DEM predicts the special-temporal position and orientation for each particle; XDEM additionally estimates properties such as the internal temperature and/or species distribution. These predictive capabilities are further extended by an interaction to fluid flow by heat, mass and momentum transfer and impact of particles on structures. These superior features as compared to traditional and pure continuum mechanic approaches are highlighted by predicted examples of relevant engineering applications. [less ▲]

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See detailDiscrete Element Modeling of Inter-Granular Bonds between Snow Grains
Michael, Mark UL; Nicot, Francios; Peters, Bernhard UL

in PARTEC - International Congress on Particle Technology (2013, April)

The mechanical behaviour of snow was long studied to help predict natural hazards, like avalanches. For those predictions the behaviour of snow deforming at low strain rates is of importance. On the other ... [more ▼]

The mechanical behaviour of snow was long studied to help predict natural hazards, like avalanches. For those predictions the behaviour of snow deforming at low strain rates is of importance. On the other hand, a large group of industrial applications concerning trafficability and transportation safety also benefit from the understanding of snow physics. These applications requiring an understanding of the high strain rate behaviour of snow. The material behaviour of snow is based on its micro-structure. The micro-structure consists of ice grains connected by ice bonds building up an open-foam like structure. The macroscopic response of a snow pack to loading is determined by the deformation and failure of its bonds and the inter-granular friction whiles rearrangement of the grains. The work reported here proposes an inter-granular snow model developed and deployed using a discrete element technique. The goal is to understand the material behaviour of dry snow at high strain rates, from 0.01s^-1 up to 100s^-1. The developed algorithm predicts the displacement of the individual grains due to inter-granular contact and bond forces. The micro-structure of a snow pack is represented by generating an ensemble of explicit geometrical shapes describing the individual ice grains and bonds. The distributions of grain size and position are generated by gravitational deposition and by applying a fractal algorithm. Snow structures of densities from 200 kg/m^3 up to 600 kg/m^3 are generated. The developed inter-granular bond models assume a cylindrical neck between adjoining ice grains. Material properties and constitutive models of the hexagonal single- and poly-crystal Ih ice are used to describe the material behaviour of each individual bond. Simulations of tensile and compression tests have been conducted using samples of 10^3 up to 10^5 grains. Here, results of different parametric studies are reported. Assessed are the dependences of the macroscopic snow behaviour on microstructural properties and mechanical properties on grain-scale. These results are compared to experimental measurements and corresponding finite element simulations. The calculation results enable to identify primary deformation mechanism at the given strain rates. [less ▲]

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See detailExtended Discrete Element Method (XDEM) to Model Heterogeneous Reactions in Packed Beds
Hoffmann, Florian UL; Peters, Bernhard UL

in PARTEC - International Congress on Particle Technology (2013, April)

Packed beds, due to their high surface-area-to-volume-ratio, are widely used for chemical reactors, such as catalytic or pebble bed reactors, blast furnaces or as heat exchanging units. Depending on the ... [more ▼]

Packed beds, due to their high surface-area-to-volume-ratio, are widely used for chemical reactors, such as catalytic or pebble bed reactors, blast furnaces or as heat exchanging units. Depending on the mode of packing, structured or random, a different degree of heterogeneity is introduced. For stable and efficient process handling local quantities such as temperature or concentration of chemical species are of major interest. Direct measurement of such quantities has proven very difficult or unfeasable due to the morphology of the bed. Hence, numerical modeling can help to gain insights into inaccessible parts of such reactors. The objective of this contribution is to introduce a discrete numerical approach that describes heterogeneous reaction processes within packed and moving beds. The so-called Extended Discrete Element Method (XDEM) is used to account for convective heat and mass transfer within porous media. Both motion and chemical conversion of particulate material can be dealt with. A granular medium consists of an ensemble of particles of which each exhibits individual chemical and mechanical properties. Dynamics of solid particles is accounted for by the known discrete element approach. In addition physicochemical conversion of an individual particle like drying, gasification or redox reactions are accounted for by transient differential equations (species, energy, momentum) on a particle scale. Predictions include properties such as temperature and species distribution inside a particle. The general and modular formulation of the model allows for application to any chemical process involving heterogeneous reactions. Chemical interaction between multiple particles takes place through gaseous intermediates by heat and mass transfer. Computational Fluid Dynamics is applied for the gaseous continuum in the voidage between particles. The presented model can act as tool to gain valuable insights into chemical processes inside packed beds such as blast furnace iron making or gasification of biomass. It can serve as a toolbox for prediction, analysis and optimization of a variety of process parameters such as residence time, conversion progress, burden charging and gas flow patterns. As an example a section of the burden in a blast furnace is focused on. [less ▲]

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See detaileXtended Discrete Element Method used for convective heat transfer predictions
Estupinan Donoso, Alvaro Antonio UL; Hoffmann, Florian UL; Peters, Bernhard UL

in International Review of Mechanical Engineering (2013), 7(2), 329-336

Packed bed reactors dominate a broad range of engineering applications. In a packed bed reactor, heat is transferred from the solid particles to the gas flow stream through the void space between ... [more ▼]

Packed bed reactors dominate a broad range of engineering applications. In a packed bed reactor, heat is transferred from the solid particles to the gas flow stream through the void space between particles. Using a XDEM approach, continuous and discrete phases have been coupled in order to predict convective heat transfer between solid and fluid within packed beds. For the solid matrix a discrete intra-particle model, namely DPM, was used to solve for each particle of the bed, and a CFD tool was employed to resolve the fluid flow. [less ▲]

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See detailUnified Design for Parallel Execution of Coupled Simulations using the Discrete Particle Method
Besseron, Xavier UL; Hoffmann, Florian UL; Michael, Mark UL et al

in Proceedings of the Third International Conference on Parallel, Distributed, Grid and Cloud Computing for Engineering (2013)

This paper presents the enhanced design of the Discrete Particle Method (DPM), a simulation tool which provides high quality and fast simulations to solve a broad range industrial processes involving ... [more ▼]

This paper presents the enhanced design of the Discrete Particle Method (DPM), a simulation tool which provides high quality and fast simulations to solve a broad range industrial processes involving granular materials. It enables to resolve mechanical and thermodynamics problems through different simulation modules (motions, chemical conversion). This new design allows to transparently couple the simulation modules in parallel execution. It relies on a unified interface and timebase of the simulation modules and a flexible decomposition in cells of the simulation space. Experimental results study the behavior of the Orthogonal Recursive Bisection (ORB) partitioning algorithm. A good scalability is achieved as the parallel execution on a distributed platform provides a 17-times speedup using 64 processes. [less ▲]

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See detailDie Extended Discrete Element Method (XDEM) für multiphysikalische Anwendungen
Peters, Bernhard UL; Besseron, Xavier UL; Estupinan Donoso, Alvaro Antonio UL et al

Scientific Conference (2013)

A vast number of engineering applications include a continuous and discrete phase simultaneously, and therefore, cannot be solved accurately by continuous or discrete approaches only. Problems that ... [more ▼]

A vast number of engineering applications include a continuous and discrete phase simultaneously, and therefore, cannot be solved accurately by continuous or discrete approaches only. Problems that involve both a continuous and a discrete phase are important in applications as diverse as pharmaceutical industry e.g. drug production, agriculture food and processing industry, mining, construction and agricultural machinery, metals manufacturing, energy production and systems biology. A novel technique referred to as Extended Discrete Element Method (XDEM) is developed, that offers a significant advancement for coupled discrete and continuous numerical simulation concepts. XDEM treats the solid phase representing the particles and the fluidised phase usually a fluid phase or a structure as two distinguished phases that are coupled through heat, mass and momentum transfer. An outstanding feature of the numerical concept is that each particle is treated as an individual entity that is described by its thermodynamic state e.g. temperature and reaction progress and its position and orientation in time and space. The thermodynamic state includes one-dimensional and transient distributions of temperature and species within the particle and therefore, allows a detailed and accurate characterisation of the reaction progress in a fluidised bed. Thus, the proposed methodology provides a high degree of resolution ranging from scales within a particle to the continuum phase as global dimensions. These superior features as compared to traditional and pure continuum mechanics approaches are applied to predict drying of wood particles in a packed bed and impact of particles on a membrane. Pre- heated air streamed through the packed bed, and thus, heated the particles with simultaneous evaporation of moisture. Water vapour is transferred into the gas phase at the surface of the particles and transported to the exit of the reactor. A rather inhomogeneous drying process in the upper part of the reactor with higher temperatures around the circumference of the inner reactor wall was observed. The latter is due to increased porosity in conjunction with higher mass flow rates than in the centre of the reactor, and thus, augmented heat transfer. A comparison of the weight loss over time agreed well with measurements. Under the impact of falling particles the surface of a membrane deforms that conversely affects the motion of particles on the surface. Due to an increasing vertical deformation particles roll or slide down toward the bottom of the recess, where they are collected in a heap. Furthermore, during initial impacts deformation waves are predicted that propagate through the structure, and may, already indicate resonant effects already before a prototype is built. Hence, the Extended Discrete Element Method offers a high degree of resolution avoiding further empirical correlations and extends the knowledge into the underlying physics. Although most of the work load concerning CFD and FEM is arranged in the ANSYS workbench, a complete integration is intended that allows for a smooth workflow of the entire simulation environment. [less ▲]

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See detailNumerical prediction of the bulk density of granular particles of di erent geometries
Peters, Bernhard UL; Samiei, Kasra UL; Berhe, Girma UL

in KONA Powder and Particle Journal (2013)

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See detailEnhanced Thermal Process Engineering by the Extended Discrete Element Method (XDEM)
Peters, Bernhard UL; Besseron, Xavier UL; Estupinan Donoso, Alvaro Antonio UL et al

in Universal Journal of Engineering Science (2013), 1

A vast number of engineering applications <br />include a continuous and discrete phase simultaneously, <br />and therefore, cannot be solved accurately by continu- <br />ous or discrete approaches only ... [more ▼]

A vast number of engineering applications <br />include a continuous and discrete phase simultaneously, <br />and therefore, cannot be solved accurately by continu- <br />ous or discrete approaches only. Problems that involve <br />both a continuous and a discrete phase are important <br />in applications as diverse as pharmaceutical industry <br />e.g. drug production, agriculture food and process- <br />ing industry, mining, construction and agricultural <br />machinery, metals manufacturing, energy production <br />and systems biology. A novel technique referred to as <br />Extended Discrete Element Method (XDEM) is devel- <br />oped, that o ers a signi cant advancement for coupled <br />discrete and continuous numerical simulation concepts. <br />The Extended Discrete Element Method extends the <br />dynamics of granular materials or particles as described <br />through the classical discrete element method (DEM) to <br />additional properties such as the thermodynamic state <br />or stress/strain for each particle coupled to a continuum <br />phase such as <br />uid <br />ow or solid structures. Contrary <br />to a continuum mechanics concept, XDEM aims at <br />resolving the particulate phase through the various <br />processes attached to particles. While DEM predicts <br />the spacial-temporal position and orientation for each <br />particle, XDEM additionally estimates properties such <br />as the internal temperature and/or species distribution. <br />These predictive capabilities are further extended by an <br />interaction to <br />uid <br />ow by heat, mass and momentum <br />transfer and impact of particles on structures. [less ▲]

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See detailA Numerical Approach to Predict Sulphur Dioxide Emissions During Switchgrass Combustion
Peters, Bernhard UL; Smula, Joanna UL

in Chemical and Process Engineering (2013)

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See detailThe Extended Discrete Element Method (XDEM) for Multi-Physics Applications
Peters, Bernhard UL

Scientific Conference (2013)

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See detailDie Extended Discrete Element Method (XDEM) als integraler Ansatz für reagierende Mehrphasenströmungen
Peters, Bernhard UL; Mahmoudi, Amir Houshang UL

in 26. Deutscher Flammentag Verbrennung und Feuerung (2013)

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See detailDie Extended Discrete Element Method (XDEM) für multiphysikalische Anwendungen
Peters, Bernhard UL; Besseron, Xavier UL; Dziugys, Algis et al

Scientific Conference (2013)

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See detailExperimental and numerical investigation into the residence time distribution of granular particles on forward and reverse acting grate
Samiei, Kasra UL; Peters, Bernhard UL

in Chemical Engineering Science (2013)

Forward andreverseactinggratesarewidelyemployedinwaste-to-energyplants.Inordertopredict the motionofsolidgranularparticlesandoptimisethedesignofsuchsystems,DiscreteElement Method(DEM)isincreasinglyused ... [more ▼]

Forward andreverseactinggratesarewidelyemployedinwaste-to-energyplants.Inordertopredict the motionofsolidgranularparticlesandoptimisethedesignofsuchsystems,DiscreteElement Method(DEM)isincreasinglyused.Theobjectiveofthispaperistopredictthedynamicsofgranular particlesonforwardandreverseactinggratesbyapplyingDEM.Theresidencetimedistributionofsolid particlesisanalysedbyDEMandcomparedwithexperimentalresultsinapilotplantexcluding combustion.TheresultsindicateaverygoodconsistencybetweenDEMandexperimentalresults, highlightingthepromisingcapabilitiesofDEMinpredictingthedynamicsofgranularparticlesingrate systems.CouplingDEMwithcomputationalfluiddynamicstechniquescanfurtheradvancethemethod to accountforthermalconversionofsolidfuelsinfuturework. [less ▲]

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See detailAssessment of the potentials of implicit integration method in discrete element modelling of granular matter
Samiei, Kasra UL; Peters, Bernhard UL; Bolten, Matthias et al

in Computers & Chemical Engineering (2013)

Discrete element method (DEM) is increasingly used to simulate the motion of granular matter in engineering devices. DEM relies on numerical integration to compute the positions and velocities of ... [more ▼]

Discrete element method (DEM) is increasingly used to simulate the motion of granular matter in engineering devices. DEM relies on numerical integration to compute the positions and velocities of particles in the next time step. Typically, explicit integration methods are utilized in DEM. This paper presents a systematic assessment of the potentials of implicit integration in DEM. The results show that though the implicit integration enables larger time steps to be used compared to the common explicit methods, the overall speed up is overruled by higher computational costs of the implicit method. [less ▲]

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