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Convective drying of wood chips:Accelerating coupled DEM-CFD simulations with parametrized reduced single particle models

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Particuology 2024年第1期84卷 158-167页

作者： Lucas Reineking Jonas Fischer Ali Mjalled Enric Illana Siegmar Wirtz Viktor Scherer Martin Monnigmann Automatic Control and System theory Ruhr-Universität-BochumUniversitätstraße 150Bochum44801Germany Energy Plant technology Ruhr-Universität-BochumUniversitätstraße 150Bochum44801Germany

the simulation of industry-scale reactive bulks is challenging due to the complex interaction between fluid and particles.the particles in the bulk and their interaction with the fluid flow can be described by combined Discrete Element Method-Computational Fluid Dynamics(DEM-CFD)models.However,the computational cost of the Finite Volume(FV)methods deployed in these models can become prohibi-tively expensive,especially for high inner-particle resolution.Single particle Reduced Models(RMs)can be used to achieve both fast and accurate descriptions of the processes in each particle.As an example of bulk systems comprising heat and mass transfer,we compared FV and RM simulations for the drying of wood chips in a bulk reactor.A manifold-based nonlinear interpolation was applied to resolve changing boundary conditions for the RM.Our simulations showed that RMs provide accurate values for the thermodynamic state variables of the particles.Furthermore,the time required for the bulk simulation was reduced by 67%with the RMs.It is evident that simulations with high inner-particle resolution can be accelerated by RMs if manifold-based nonlinear interpolation is used to address changing boundary conditions.

关键词： Reduced model Reactive bulk Discrete element method Manifold-based interpolation Drying of porous mediaDEM-CFD

A simulation study on spatial and time resolution for a cost-effective positron emission particle tracking system

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Particuology 2024年第5期88卷 312-322页

作者： Josephine Oppotsch Matthias Steinke Miriam Fritsch Fritz-Herbert Heinsius thomas Held Nikoline Hilse Viktor Scherer Ulrich Wiedner ruhr-universität bochum Institut für Experimentalphysik I44801 BochumGermany ruhr-universität bochum Lehrstuhl für Energieanlagen und Energieprozesstechnik44801 BochumGermany

this work is the second part of a simulation study investigating the processing of densely packed and moving granular assemblies by positron emission particle tracking (PEPt).Since medical positron emission tomography (PEt) scanners commonly used for PEPt are very expensive,a PEt-like detector system based on cost-effective organic plastic scintillator bars is being developed and tested for its capabilities.In this context,the spatial resolution of a resting positron source,a source moving on a freely designed model path,and a particle motion given by a discrete element method (DEM) simulation is studied using Monte Carlo simulations and the software toolkit Geant4.this not only extended the simulation and reconstruction to a moving source but also significantly improved the spatial resolution compared to previous work by adding oversampling and iteration to the reconstruction algorithm.Furthermore,in the case of a source following a trajectory developed from DEM simulations,a very good resolution of about 1 mm in all three directions and an average 3D deviation between simulated and reconstructed events of 2.3 mm could be determined.thus,the resolution for realistic particle motion within the generic grate system (which is the test rig for further experimental studies) is well below the smallest particle size.the simulation of the dependence of the reconstruction accuracy on tracer particle location revealed a nearly constant efficiency within the entire detector system,which demonstrates that boundary effects can be neglected.

关键词： Positron emission particle tracking Monte Carlo method time-of-flight Plastic scintillators Silicon photomultipliers(SiPMs)

Unraveling the gut-brain axis:the impact of steroid hormones and nutrition on Parkinson's disease

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Neural Regeneration Research 2024年第10期19卷 2219-2228页

作者： Paula Maria Neufeld Ralf A.Nettersheim Veronika Matschke Matthias Vorgerd Sarah Stahlke Carsten theiss Department of Cytology Institute of AnatomyMedical FacultyRuhr-University BochumBochumGermany Department of Visceral Surgery University Hospital BergmannsheilRuhr-University BochumBochumGermany Department of Neurology Heimer Institute for Muscle ResearchUniversity Hospital BergmannsheilRuhr-University BochumBochumGermany

this comprehensive review explores the intricate relationship between nutrition,the gut microbiome,steroid hormones,and Parkinson's disease within the context of the gut-brain axis.the gut-brain axis plays a pivotal role in neurodegenerative diseases like Parkinson's disease,encompassing diverse components such as the gut microbiota,immune system,metabolism,and neural pathways.the gut microbiome,profoundly influenced by dietary factors,emerges as a key player.Nutrition during the first 1000 days of life shapes the gut microbiota composition,influencing immune responses and impacting both child development and adult health.High-fat,high-sugar diets can disrupt this delicate balance,contributing to inflammation and immune dysfunction.Exploring nutritional strategies,the Mediterranean diet's anti-inflammatory and antioxidant properties show promise in reducing Parkinson's disease risk.Microbiome-targeted dietary approaches and the ketogenic diet hold the potential in improving brain disorders.Beyond nutrition,emerging research uncovers potential interactions between steroid hormones,nutrition,and Parkinson's disease.Progesterone,with its anti-inflammatory properties and presence in the nervous system,offers a novel option for Parkinson's disease therapy.Its ability to enhance neuroprotection within the enteric nervous system presents exciting prospects.the review addresses the hypothesis thatα-synuclein aggregates originate from the gut and may enter the brain via the vagus nerve.Gastrointestinal symptoms preceding motor symptoms support this hypothesis.Dysfunctional gut-brain signaling during gut dysbiosis contributes to inflammation and neurotransmitter imbalances,emphasizing the potential of microbiota-based interventions.In summary,this review uncovers the complex web of interactions between nutrition,the gut microbiome,steroid hormones,and Parkinson's disease within the gut-brain axis framework.Understanding these connections not only offers novel therapeutic insights but also illuminates the origins of neurode

关键词： diet gut-brain axis microbiome neurodegenerative diseases nutrition Parkinson's disease progesterone steroid hormones

Investigating the inflow into a granular bed using a locally resolved method

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Particuology 2024年第2期85卷 89-101页

作者： Maximilian Brommer Maik Scharnowski Enric Illana Mahiques Siegmar Wirtz Viktor Scherer ruhr university bochum Institute of Energy Plant TechnologyUniversitätsstraβe 15044780BochumGermany

Discrete Element Method-Computational Fluid Dynamics(DEM/CFD)simulations of industrial-scale granular systems employ spatial averaging(porous media approach)for the fluid-particle interaction in the whole domain,which can lead to poor accuracy,for instance at flow inlets,as local particle bulk morphology is not resolved.this paper presents an approach where the interstitial flow in crucial areas with large gradients can be resolved locally in an otherwise unresolved domain,so that a mixed resolved-unresolved method is realized.As a generic example to show the feasibility and performance of the new approach,the inflow of ambient air into a flat-bottom hopper through a narrow orifice is investigated.In an experimental setup,the vertical profile of the pressure decay through the inlet and across the packing is chosen for com-parison with respective simulations.Results obtained with the conventional porous media method and the locally resolved approach are compared to these experiments for varying volume flow rates and for two different particle shapes.Spheres of different size as well as dodecahedrons are examined.It is found that although averaging methods already provide good approximations,the locally resolved method can improve the result especially when conventional drag laws are not applicable due to wall effects or if large velocity gradients exist.

关键词： DEM/CFD Packed bed Pressure drop

A numerical and experimental comparison of heat transfer in a quasi two-dimensional packed bed

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Particuology 2024年第1期84卷 136-144页

作者： Matthias tyslik Mirko Ebert Martin Schiemann Siegmar Wirtz Christian Lessig Department of Energy Plant technology Ruhr-University BochumGermany Institute for Simulation and Graphics Otto-von-Guericke-Universität MagdeburgGermany

Heat transfer plays a major role in many industrial processes taking place in packed beds.An accurate and reliable simulation of the heat exchange between particles is therefore crucial for a reliable operation and to optimize the processes in the bed.the discrete ordinates method(DOM)provides an established numerical technique to model radiative heat transfer in granular media that offers the possibility to consider the directional dependence of the radiation propagation.In this work,DOM is compared with Monte Carlo ray tracing,which provides an alternative method for heat transfer simulations.Geomet-rically simple configurations are used to investigate the influence of the angular discretization on the accuracy of the results and the computation time in both methods.the obtained insights are then transferred to a more complex configuration of a quasi two-dimensional test rig consisting of metal rods for which also experimental results are available.Our results show that both DOM and Monte Carlo ray tracing allow for an accurate simulation of heat transfer in packed beds.Monte Carlo ray tracing requires thereby computation times that are surprisingly competitive(although still somewhat slower)compared to DOM and allows for an easier computation of highly accurate reference solutions.In our preliminary comparison to the experimental test rig,Monte Carlo ray tracing also provides the advantage that it can more easily model highly specular materials such as stainless steel.Both methods are comparable for diffuse materials such as magnesium oxide.

关键词： Heat transfer Discrete ordinates method Monte Carlo ray tracing

Experimental study on influence of blade angle and particle size on particle mechanics on a batch-operated single floor of a multiple hearth furnace

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Particuology 2024年第2期85卷 224-240页

作者： Max Kriegeskorte Nikoline Hilse Phil Spatz Viktor Scherer Institute for Energy Plant technology(LEAt) Ruhr University BochumUniversitätsstraβe 15044780 BochumGermany

In industry,multiple hearth furnaces are used for the thermal treatment of particulate material.the current contribution concentrates on the experimental analysis of particle mechanics for a batch-operated single floor of a multiple hearth furnace.the particles are agitated on the circular floor by a single,rotating rabble arm equipped with three flat rabble blades of 10 mm thickness.the blade angle,defined as the angle,which the blade is inclined against the tangential direction,is varied from 0°to 90°.A single layer of spherical polyoxymethylene(POM)particles with three different diameters(5,10 and 20 mm)is placed on the floor.to analyze the results,two parameters have been extracted from image analysis when the bed of particles is agitated,first,the area not covered by particles and second,the frequency distribution of the mean distance among the particles.the particle free surface area increases with the inclination of the blades.the evolution of the particle free surface area differs for the different particle diameters.In general,the maximum particle free area for all blade angles is the largest for the 5 mm particles followed by the 20 mm particles.For the 10 mm particles,the particle free surface area starts for a blade angle of 0°at larger values than for the 20 mm particles but the values fall below the values for the 20 mm particles for larger blade angles.the reason for this behavior is discussed in detail.the mean distance among the particles is a parameter characterizing the length scales dominating the effects on the floor.the frequency distribution of the mean distance among particles provides infor-mation about the morphology of the particle bulk,for example,whether the free surface area is inter-spersed with particles.

关键词： Hearth furnace floor Particle movement Spherical particles Particle free surface area Mean distance among particles

Shape-changing particles for locally resolved particle geometry in DEM simulations

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Particuology 2024年第6期89卷 185-190页

作者： Enric Illana Klidi Qyteti Maik Scharnowski Maximilian Brömmer Siegmar Wirtz Viktor Scherer Institute of Energy Plant technology Ruhr-University BochumBochumGermany

taking into account the complex shape of particles in discrete element method (DEM) simulations of large-scale granular systems is computationally demanding due to the time-consuming contact detection algorithms for polyhedral particles. In this short communication, a novel approach that locally resolves the particle shapes where needed and uses a simplified representation elsewhere, to accelerate simulations without compromising accuracy, is presented. For this purpose, a method employing a smooth transition of the particle shape representation from analytical spheres to shape-resolving polyhedra is introduced in DEM. the feasibility and correct implementation of this approach are demonstrated through simulations of hopper discharge involving spherical and dodecahedral particles from a flat bottom silo or shaft kiln. the model capabilities, in terms of accuracy as well as reduction in computational effort, are quantified for a moving bed with continuous outflow.

关键词： Polyhedron Size change Shape change Locally resolved DEM

Wear dependent virtual flow rate sensor for progressing cavity pumps with deformable stator

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Petroleum Science 2024年第2期21卷 1346-1353页

作者： Jens Müller Sebastian Leonow Johannes Schulz Christian Hansen Martin M onnigmann ruhr-universit at bochum Universit atsstraûe 150Bochum44801Germany SEEPEX GmbH Scharnh olzstraûe 344Bottrop46240Germany

this contribution presents a novel wear dependent virtual flow rate sensor for single stage single lobe progressing cavity pumps. We study the wear-induced material loss of the pump components and the impact of this material loss on the volumetric efficiency. the results are combined with an established backflow model to implement a backflow calculation procedure that is adaptive to wear. We use a laboratory test setup with a highly abrasive fluid and operate a pump from new to worn condition to validate our approach. the obtained measurement data show that the presented virtual sensor is capable of calculating the flow rate of a pump being subject to wear during its regular operation.

关键词： Backflow Progressing cavity pump Virtual sensor Wear

Experimental investigation of radiative heat propagation in a simplified generic packed bed

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Particuology 2024年第5期88卷 149-160页

作者： Matthias tyslik Lukas Pörtner Siegmar Wirtz Martin Schiemann Institute of Energy Plant technology Ruhr-University Bochum44780 BochumGermany

A novel test rig for the investigation of radiative heat transfer in packed beds has been developed and is introduced with representative experimental results.the individual components and the calibration are discussed.the generic packed bed is realized in a simplified way by an arrangement of parallel rods,which represent particles in pseudo-2D.In this arrangement,electrically heated rods provide the radiation propagating through the rod array to heat the passive counterparts.A sophisticated temperature-control scheme with a large number of thermocouples and infrared-imaging provides in-depth information about heat transfer in the system.Spectral radiation intensities are determined with a Fourier-transform infrared spectroscopy,which has been modified and validated for this specific application.In order to compare the influence of different surface properties of particles on the heat propagation and surface reflections,rod samples made of stainless steel and magnesium oxide are used.the influence of material properties becomes clearly visible by comparing the high radiation intensities resulting from a stainless steel rod array to the same geometry built from magnesium oxide rods.In addition,the influence of the surface properties is particularly evident in the infrared images since the reflections are significantly higher for the stainless steel samples than for the magnesium oxide samples.the experimental results in the current work demonstrate the ability of the test rig to provide data with a well-defined accuracy as a validation base for numerical radiation simulations in packed beds.

关键词： thermal radiation Spectral reflections Fourier-transform infrared spectroscopy