Letteratura scientifica selezionata sul tema "Modèle CFD-DEM"
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Articoli di riviste sul tema "Modèle CFD-DEM"
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Chen, Yong, Chuanliang Yan, Yuanfang Cheng, Zhongying Han e Yang Li. "Study on Agglomeration and Plugging Behavior of Fine Particles in Reservoir Based on DEM-CFD Coupling". Journal of Physics: Conference Series 2834, n. 1 (1 ottobre 2024): 012158. http://dx.doi.org/10.1088/1742-6596/2834/1/012158.
Testo completoAbstract (sommario):
Abstract Given the particularity, significance, and complexity of particle migration behavior in fine silt sand hydrate reservoirs, the agglomeration and plugging behavior of free fine particles are mainly studied. Based on the discrete element method (DEM) and computational fluid dynamics (CFD), the DEM-CFD coupled 3D wellbore sand production numerical model is established and verified. The DEM module divides the reservoir particles into coarse and fine components according to the actual particle size distribution, and assigns adhesive and non-adhesive rolling resistance linear models, respectively. The CFD module uses the finite volume method to solve the incompressible Darcy flow in coarse grids. The results show that the DEM-CFD coupled numerical model established can effectively simulate the phenomenon of fine particle agglomeration during particle migration; Compared with the condition without particle agglomeration, fine particle agglomeration can lead to lower wellbore sand production and more severe pore blockage and permeability loss in the surrounding reservoir; The influences of different production and reservoir parameters such as flow rate, porosity and mud content on the variation of wellbore sand production and reservoir permeability under the condition of fine particle agglomeration is further determined, and relevant production measures and suggestions are put forward. The research results help to clarify the sand production mechanism and characteristics of fine silt sand reservoirs and are expected to provide theoretical and technical support for the efficient and safe development of natural gas hydrate resources in fine silt sand reservoirs.
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Lengyel, Tamás, Attila Varga, Ferenc Safranyik e Anita Jobbik. "Coupled Numerical Method for Modeling Propped Fracture Behavior". Applied Sciences 11, n. 20 (17 ottobre 2021): 9681. http://dx.doi.org/10.3390/app11209681.
Testo completoAbstract (sommario):
Hydraulic fracturing is a well-known production intensification technique in the petroleum industry that aims to enhance the productivity of a well drilled mostly in less permeable reservoirs. The process’s effectiveness depends on the achieved fracture conductivity, the product of fracture width, and the permeability of the proppant pack placed within the fracture. This article presents an innovative method developed by our research activity that incorporates the benefit of the Discrete—and Finite Element Method to describe the in situ behavior of hydraulic fractures with a particular emphasis on fracture conductivity. DEM (Discrete Element Method) provided the application of random particle generation and non-uniform proppant placement. We also used FEM (Finite Element Method) Static Structural module to simulate the elastic behavior of solid materials: proppant and formation, while CFD (Computational Fluid Dynamics) module was applied to represent fluid dynamics within the propped fracture. The results of our numerical model were compared to data of API RP-19D and API RP-61 laboratory measurements and findings gained by publishers dealing with propped fracture conductivity. The match of the outcomes verified the method and encouraged us to describe proppant deformation and embedment and their effect as precisely as possible. Based on the results, we performed sensitivity analysis which pointed out the impact of several factors affecting proppant embedment, deformation, and fracture conductivity and let one be aware of a reasonable interpretation of propped hydraulic fracture operation. However, DEM–CFD coupled models were introduced regarding fracturing before, to the best of our knowledge, the developed workflow of coupling DEM–FEM–CFD for modeling proppant-supported fracture behavior has not been applied yet, thus arising new perspectives for explorers and engineers.
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Ren, Dezhi, Haolin Yu, Ren Zhang, Jiaqi Li, Yingbo Zhao, Fengbo Liu, Jinhui Zhang e Wei Wang. "Research and Experiments of Hazelnut Harvesting Machine Based on CFD-DEM Analysis". Agriculture 12, n. 12 (9 dicembre 2022): 2115. http://dx.doi.org/10.3390/agriculture12122115.
Testo completoAbstract (sommario):
To solve the problem of difficult hazelnut harvesting in mountainous areas of Liaoning, China, a small pneumatic hazelnut harvesting machine was designed, which can realize negative pressure when picking up hazelnut mixtures and positive pressure when cleaning impurities. The key structure and parameters of the harvesting machine were determined by constructing a mechanical model of the whole machine and combining theoretical analysis and operational requirements. To explore the harvesting machine scavenging performance, Liaoning hazelnut No. 3 with a moisture content of 7.47% was used as the experimental object. Firstly, the terminal velocity of hazelnuts and fallen leaves was measured using a material suspension velocity test bench. Secondly, the gas–solid two-phase flow theory was applied comprehensively, and the motion state, particle distribution, and air flow field distribution of hazelnuts from the inlet to the outlet of the pneumatic conveying device were simulated and analyzed using the coupling of computational flow fluid dynamics method (CFD) and discrete element method (DEM) to evaluate the cleaning performance from the perspective of the net fruit rate of hazelnuts in the cleaning box. Finally, a Box–Behnken design experiment was conducted with the sieve plate angle, the distance of the sieve plate, and the air flow velocity as factors and the net fruit rate of hazelnuts as indicators to explore the influence of the three factors on the net fruit rate of hazelnuts. The parameter optimization module of Design-Expert software was used to obtain the optimal combination of parameters for the factors. The experimental results show that the test factors affecting the test index are the following: the air flow rate, the angle of the screen plate, and the distance of the screen plate. The best combination of parameters was an air flow velocity of 14.1 m∙s−1, a sieve plate angle of 55.7°, and a distance of the sieve plate of 33.2 mm. The net fruit rate of hazelnuts was 95.12%. The clearing performance was stable and can guarantee the requirements of hazelnut harvester operation, which provides a certain theoretical basis for the design of a nut harvester.
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Chen, An, e Yonggang Yu. "Motion Characteristics and Distribution Laws of Particles in the Launching System with a Sequence-Change Structure". Processes 12, n. 7 (11 luglio 2024): 1454. http://dx.doi.org/10.3390/pr12071454.
Testo completoAbstract (sommario):
There is a fundamental issue in the launching system with the modular charge technology, which is an unsteady gas–solid flow in the sequence-change space within a short period of time. It leads to complex particle behavior, causing the strong pulsation of particle energy released during the combustion process. As a result, a large initial pressure wave is generated, which damages the launching stability. In this work, a 3D gas–solid flow model is developed based on the computational fluid dynamics–discrete element method (CFD-DEM) model to analyze the particle behavior in the launching system with different numbers of modules. The rationality of the model is verified through the experiment. It is found that the particles near the cover of the rightmost module move out of the module rapidly and collide with the right face of the chamber, forming a retained particle layer. When particles are stationary, the distribution of particles consists of slope accumulations and horizontal accumulation. With the increase in the module number, the position changes of all tracer particles are decreased, both the thickness and the length of the horizontal shape are increased, the variation laws of the slope stack height change from exponential to linear, and the distribution of particles becomes uniform.
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Chen, A., e Y. G. Yu. "Effect of Initial Loading Position on the Propellant Particles Distribution in Two-module Charge". Journal of Physics: Conference Series 2460, n. 1 (1 aprile 2023): 012015. http://dx.doi.org/10.1088/1742-6596/2460/1/012015.
Testo completoAbstract (sommario):
Abstract The propellant particles distribution in the ignition process of the modular charge has a significant effect on the interior ballistic stability. Thereinto, the particles final distribution is determined by the particles motion process. Based on the CFD-DEM method, a 3D transient gas-solid flow model is constructed to investigate the motion process and the dispersion of propellant particles. Moreover, the cold state test of the ignition process of modular charge is accomplished based on a visual ignition test platform. The simulated data are consistent with the test one. Furthermore, the effect of the initial loading position on the propellant particles distribution of two-module charge is predicted by the numerical simulation. All of two-module cases show that the distributions of particles are made up of a gentle-downhill, a horizontal, and a steep-uphill accumulation. As the initial loading position of modules moves to the right, the slope angle of the uphill is decreased first and then increased, with the minimum slope angle of 20.5°. When the initial loading position of modules is 40mm, the spatial distribution gradient of particles gets the minimum in the uphill accumulation area, and the particles axial-distribution is the most uniform.
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Chen, Juntong, Man Ge e Lin Li. "The Effect of the Aeration Condition on the Liquid–Solid Material Mixing in a Stirred Tank with a Single-Layer Impeller". Applied Sciences 13, n. 15 (7 agosto 2023): 9021. http://dx.doi.org/10.3390/app13159021.
Testo completoAbstract (sommario):
In order to increase industrial production quality and efficiency, it is essential to understand how the aeration and no-aeration condition affects liquid and solid material mixing in the stirred tank. Due to complicated shear flows, the related mass-transfer mechanism confronts numerous difficulties. This paper put forward an improved computational fluid dynamics and discrete element method (CFD–DEM) modeling approach to explore the effect mechanism of aeration conditions on liquid–solid material mixing. Firstly, a mass-transfer dynamic model is set up with a volume of fluid and piecewise linear interface construction (VOF–PLIC) coupling strategy to explore flow modes and vorticity evolution trends under aeration control. Then, a self-developed interphase coupling interface is utilized to modify the coupling force and porosity of the porous media model in the DEM module, and random dispersion properties of the particle phase under non-aeration and aeration are obtained. Results show that the aeration and flow-blocking components transform fluid tangential speeds into axial and radial speeds, which can improve the material mixing quality and efficiency. The mixed flow field can reach a greater turbulent process under the impeller rotation, making the particles have an intensive disorder and complex flow patterns. The enhanced motion efficiency of the vortex clusters encourages their nesting courses and improves cross-scale mixed transport. It can serve as some reference for the three-phase flow mixing mechanism, vorticity distribution law, and particle motion solution and has a general significance for battery homogeneous mixing, biopharmaceutical processes, and chemical process extraction.
Tesi sul tema "Modèle CFD-DEM"
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Badran, Youssef. "Modélisation multi-échelle des forces d'adhésion dans les lits fuidisés gaz-solide". Electronic Thesis or Diss., Université de Toulouse (2023-....), 2024. http://www.theses.fr/2024TLSEP111.
Testo completoAbstract (sommario):
Le dépassement de la chute de pression du lit à la vitesse minimale de fluidisation, qui se produit pendant la transition d'un état de lit fixe à un état de lit fluidisé, est un phénomène courant pour les particules fines classées dans le groupe A selon la classification de Geldart. Ces particules présentent une hystérésis entre les courbes de chute de pression pour les trajectoires de vitesse de gaz décroissante et croissante. Cette étude utilise deux modèles de pression de particules adhésives dans des simulations de modèles à deux fluides pour incorporer l'influence de la force de Van der Waals interparticulaire, dans le but de prédire le dépassement de la pression. Le premier modèle de pression adhésive, développé dans le cadre de la théorie cinétique des écoulements granulaires rapides, n'a pas réussi à capturer le dépassement en raison de la prévalence de contacts multiples et prolongés dans les lits fixes. Nous avons proposé une fermeture alternative basée sur le nombre de coordination, générant une contribution adhésive significativement plus élevée que le modèle de la théorie cinétique et reproduisant avec succès le dépassement de la chute de pression.En outre, nous avons construit une base de données numériques CFD-DEM (Computational Fluid Dynamics-Discrete Element Method) pour prédire l'hystérésis dans la chute de pression. Cette base de données peut guider la formulation d'une équation de transport eulérienne pour le nombre de coordination, permettant l'incorporation des effets de l'historique des déformations. Nous avons étudié l'impact de la force de Van der Waals et de la friction statique sur la fluidisation des solides fins à l'échelle moyenne en utilisant des simulations CFD-DEM et leur rôle dans l'apparition du phénomène de dépassement de pression. Notre analyse examine des paramètres tels que la chute de pression du gaz, le vide du lit, le nombre de coordination, les pressions répulsives et adhésives des solides, le gradient vertical de vitesse des solides, le tenseur de tissu et la contrainte de cisaillement particule-paroi tout au long des processus de défluidisation et de fluidisation. Nous avons démontré qu'il est nécessaire de prendre en compte l'adhésion de Van der Waals pour prédire l'expansion homogène du lit sur toute la gamme des vitesses, du minimum requis pour la fluidisation au minimum pour le bullage. L'ensemble de données CFD-DEM généré peut guider le développement de fermetures de contraintes solides pour les modèles à deux fluides afin d'incorporer les effets de l'adhésion de Van der Waals et de la friction statique sur l'hydrodynamique de la fluidisation, ce qui permet de prédire l'hystérésis dans la chute de pression du lit à l'échelle macroscopique. Dans ce travail, nous avons incorporé un modèle de frottement statique-dynamique dans le code CFD-DEM massivement parallèle YALES2 à l'aide d'un algorithme en deux étapes, afin de remédier aux lacunes du modèle de frottement dynamique de Coulomb, qui est pratique pour les écoulements granulaires rapides mais ne s'applique pas aux lits stationnaires. Nous avons validé notre mise en œuvre par une série de tests à macro- et micro-échelle. En outre, nous avons introduit dans YALES2 les forces de Van der Waals entre particules et entre particules et parois, et validé cet ajout à l'échelle microscopique. En outre, nous avons postulé une expression de relaxation pour le terme source dans l'équation de transport des nombres de coordination et déterminé le temps de relaxation des nombres de coordination à l'aide de données de simulation CFD-DEM. En outre, nous avons utilisé une technique de pénalisation pour coupler de manière semi-implicite les phases gazeuse et solide, en particulier par le traitement implicite des forces de traînée et d'Archimède. Cette approche vise à résoudre les problèmes de stabilité rencontrés lorsque le couplage interphase est expliciteThe overshoot in bed pressure drop at the minimum fluidization velocity, occurring during the transition from a fixed to a fluidized bed state, is a common phenomenon for fine particles categorized under Group A according to Geldart's classification. These particles exhibit hysteresis between the pressure drop curves for the decreasing and increasing gas velocity paths. This study employs two adhesive particle pressure models within two-fluid model simulations to incorporate the influence of interparticle Van der Waals force, aiming to predict the pressure overshoot. The first adhesive pressure model, developed within the kinetic theory of rapid granular flows framework, failed to capture the overshoot due to the prevalence of multiple and prolonged contacts in fixed beds. We proposed an alternative closure based on coordination number, generating a significantly higher adhesive contribution than the kinetic theory model and successfully reproducing the pressure drop overshoot.In addition, we constructed a Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) numerical database to predict hysteresis in pressure drop. This database can guide the formulation of an Eulerian transport equation for the coordination number, enabling the incorporation of deformation history effects. We explored the impact of Van der Waals force and static friction on the fluidization of fine solids at the mesoscale using CFD-DEM simulations and their role in causing the pressure overshoot phenomenon. Our analysis examines parameters such as gas pressure drop, bed voidage, coordination number, repulsive and adhesive solid pressures, vertical solid velocity gradient, fabric tensor, and particle-wall shear stress throughout the defluidization and fluidization processes. We demonstrated that it is necessary to consider the Van der Waals adhesion to predict the homogeneous expansion of the bed across the range of velocities from the minimum required for fluidization to the minimum for bubbling. The generated CFD-DEM dataset can guide the development of solid stress closures for two-fluid models to incorporate the effects of Van der Waals adhesion and static friction on fluidization hydrodynamics, allowing for the prediction of hysteresis in bed pressure drop at the macroscale.In this work, we incorporated a static-dynamic friction model into the massively parallel CFD-DEM code YALES2 using a two-step algorithm, aiming to address the shortcomings of the Coulomb dynamic friction model, which is practical for fast granular flows but not applicable to stationary beds. We validated our implementation through a series of macro- and microscale tests. Furthermore, we introduced interparticle and particle-wall Van der Waals forces into YALES2 and validated this addition at the microscale. Additionally, we postulated a relaxation expression for the source term in the coordination number transport equation and determined the coordination number relaxation time using CFD-DEM simulation data. Moreover, we employed a penalization technique to semi-implicitly couple gas and solid phases, specifically through the implicit handling of drag and Archimedes forces. This approach aimed to resolve the stability issues encountered when the interphase coupling is explicit
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Maya, Fogouang Laurez. "Transport of fine particles. Application to injectivity in geothermal reservoirs". Electronic Thesis or Diss., Orléans, 2024. http://www.theses.fr/2024ORLE1025.
Testo completoAbstract (sommario):
Lors de l’exploitation de ressources renouvelables, comme pour l’énergie géothermique, l’injection de fluides dans les réservoirs souterrains peut impacter drastiquement la perméabilité du milieu poreux au voisinage des puits d’injection. Les particules fines en suspension chargées (colloïdes), qu’elles soient initialement présentes dans les fluides injectés ou qu’elles soient détachées de la matrice poreuse parle gradient de pression, vont être transportées, s’agréger, se déposer irréversiblement ou non, et/ou conduire au colmatage des pores.La conséquence de ce colmatage des pores (filtration, pontage ou agrégation de particules) sur la perméabilité conduit à une diminution drastique de l’injectivité dans les puits pouvant entraîner leur abandon. L’étude des phénomènes de colmatage est primordiale pour mieux contrôler l’injectivité et proposer des solutions de décolmatage efficaces afin de maintenir l’exploitation des puits. Ainsi l’enjeu de ce travail porte sur la connaissance de l’évolution de la perméabilité d’un milieu poreux, lors de l’injection d’une suspension en son sein, afin de prédire la chute d’injectivité et d’optimiser des processus d’injections à travers des modèles numériques. A l’échelle des sites d’exploitation (macroscopique), les approches classiques pour modéliser le transport particulaire et le colmatage reposent sur des paramètres heuristiques et des hypothèses restrictives qui limitent leurs capacités prédictives. Notamment, la prise en compte des effets électrochimiques sur le dépôt, l’agrégation et le détachement de particule ainsi que leur rétroaction sur l’écoulement est perfectible.Dans cette thèse, il est donc question d’apporter une solution quant à la modélisation du transport colloïdal dans des milieux poreux.La stratégie adoptée est basée sur une approche de modélisation en cascade d’échelles spatio-temporelles du milieu poreux. Dans un premier temps, nous nous intéressons aux échelles microscopiques (échelle moléculaire, du pore, et du réseaux de pores) où les interfaces particule-fluide et fluide-matrice, sièges des phénomènes hydromécaniques et électrochimiques contrôlant les mécanismes de colmatage,sont bien décrites. Nous avons développé et validé une nouvelle approche numérique pour simuler le transport colloïdal à l’échelle du pore. Elle s’appuie sur une méthode Euler-Lagrange du type CFD-DEM où le fluide est décrit par une phase continue et le transport des particules est représenté par une phase discrète (suivi individuel). En particulier, notre approche s’affranchit des limitations classiques sur la taille des cellules de calcul par rapport à la taille des particules. Le modèle développé nous sert de socle pour étudier la prépondérance des grandeurs physico-chimiques sur le colmatage (vitesse d’infiltration, concentration des particules, pH et salinité de la solution,taille des pores et des particules, etc...). Dans un second temps et dans une logique de remontée en échelle, nous ne considérons les particules non plus comme des éléments discrets mais comme un champ de concentration. Pour ce faire, nous revisitons la théorie de le dépôt des colloïdes autour d’un cylindre afin de déterminer analytiquement des lois macroscopiques de cinétique de dépôt. Enfin, le modèle numérique est utilisé pour simuler la rétention de particules dans le milieux poreux. Il capture les trois principaux mécanismes de colmatage (exclusion de taille, formation d’arche, et agrégation). Il permet de déterminer des relations porosité-perméabilité et la cinétique de rétention en fonction des régimes d’écoulement, de la chimie de la solution et des propriétés de la suspension représentés par des nombres a dimensionnés adéquats. Les avancées apportées par ces travaux améliorent la compréhension des mécanismes de colmatage et guident le développement de modèles à plus larges échellesWhen exploiting renewable resources, such as geothermal energy, the injection of fluids into underground reservoirs can drastically impact the permeability of the porous medium near the injection wells. Fine suspended particles (colloids), whether initially present in the injected fluids or detached from the porous matrix by the pressure gradient, are transported, aggregated, irreversibly or reversibly deposited,and/or lead to pore clogging. The consequence of this pore-clogging (filtration, bridging, or particle aggregation) on permeability results in a drastic decrease in injectivity in the wells, potentially leading to their abandonment. Studying clogging phenomena is crucial to control injectivity better and propose effective unclogging solutions to maintain well exploitation. Thus, this work aims to understand the evolution of the permeability of a porous medium during the injection of a suspension, to predict the injectivity drop, and tooptimize injection processes through numerical models. At the scale of exploitation sites (macroscopic), classical approaches for modeling particle transport and clogging rely on heuristic parameters and restrictive assumptions that limit their predictive capabilities. Notably, considering electrochemical effects on particle deposition, aggregation, and detachment and their feedback on flow can be improved. This thesis aims to provide a solution for modeling colloidal transport in porous media. The strategy adopted is based on a cascade modeling approach across spatio-temporal scales of the porous medium. First, we focus on microscopic scales (molecular, pore, and porenetwork scale) where particle-fluid and fluid-matrix interfaces, the sites of hydromechanical and electrochemical phenomena controlling clogging mechanisms, are well described. We have developed and validated a new numerical approach to simulate colloidal transportat the pore scale. It is based on an Euler-Lagrange method of the CFD-DEM type, where a continuous phase describes the fluid, and particle transport is represented by a discrete phase (individual tracking). In particular, our approach overcomes the classical limitations on the size of computational cells relative to the size of particles. The developed model is a foundation for studying the predominance of physicochemical variables on clogging (infiltration velocity, particle concentration, solution pH and salinity, pore and particle size,etc.). Subsequently, and in a logic of upscaling, we no longer consider particles as discrete elements but as a concentration field. Todo this, we revisit the theory of colloidal deposition around a cylinder to analytically determine macroscopic deposition kinetic laws. Finally, the numerical model simulates particle retention in porous media. It captures the three main clogging mechanisms (size exclusion,arch formation, and aggregation). It allows for determining porosity-permeability relationships and retention kinetics depending on flow regimes, solution chemistry, and suspension properties represented by appropriate dimensionless numbers. The advances brought by this work improve the understanding of clogging mechanisms and guide the development of models on larger scales
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Höhne, Thomas. "Kühlmittelvermischung in Druckwasserreaktoren; Vergleich von Kühlmittelströmung und -vermischung in einem skalierten Modell des DWR Konvoi mit den Vorgängen im Originalreaktor; Rechnungen mit dem CFD-Code CFX 4.1". Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-30848.
Testo completoAbstract (sommario):
Es ergab sich die Notwendigkeit, die Vermischungseffekte mit einem 1:5 skalierten Modell nachzuvollziehen. In dieser Arbeit wurden Skalierungseffekte hervorgehoben und ein Vergleich der Strömungen im Originalreaktor und 1:5 Plexiglasmodell mit Hilfe eines numerischen Strömungsberechnungsprogrammes vollzogen. Dabei wurde das Modell und der Originalreaktor möglichtst originalgetreu abgebildet und mit den kalten Strängen zusammen modelliert.Die Vergleichsrechnungen belegen, daß es ausreichend ist, die Vermischungsvorgänge in einem mindestens 1:6.6 skalierten Modell eines DWR zu untersuchen. Die Parameter (Druck, Temperatur, Geschwindigkeit) erlauben den Aufbau als Plexiglasmodell, das eine optische Beobachtung der Vermischung ermöglicht. Das Forschungszentrum Rossendorf hat mit dem Aufbau eines 1:5 Modells 1997 begonnen.
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Höhne, Thomas. "Kühlmittelvermischung in Druckwasserreaktoren; Vergleich von Kühlmittelströmung und -vermischung in einem skalierten Modell des DWR Konvoi mit den Vorgängen im Originalreaktor; Rechnungen mit dem CFD-Code CFX 4.1". Forschungszentrum Rossendorf, 1997. https://hzdr.qucosa.de/id/qucosa%3A21911.
Testo completoAbstract (sommario):
Es ergab sich die Notwendigkeit, die Vermischungseffekte mit einem 1:5 skalierten Modell nachzuvollziehen. In dieser Arbeit wurden Skalierungseffekte hervorgehoben und ein Vergleich der Strömungen im Originalreaktor und 1:5 Plexiglasmodell mit Hilfe eines numerischen Strömungsberechnungsprogrammes vollzogen. Dabei wurde das Modell und der Originalreaktor möglichtst originalgetreu abgebildet und mit den kalten Strängen zusammen modelliert.Die Vergleichsrechnungen belegen, daß es ausreichend ist, die Vermischungsvorgänge in einem mindestens 1:6.6 skalierten Modell eines DWR zu untersuchen. Die Parameter (Druck, Temperatur, Geschwindigkeit) erlauben den Aufbau als Plexiglasmodell, das eine optische Beobachtung der Vermischung ermöglicht. Das Forschungszentrum Rossendorf hat mit dem Aufbau eines 1:5 Modells 1997 begonnen.
Libri sul tema "Modèle CFD-DEM"
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Coupled CFD-DEM Modeling: Formulation, Implementation and Application to Multiphase Flows. Wiley & Sons, Limited, John, 2016.
Cerca il testo completoCapitoli di libri sul tema "Modèle CFD-DEM"
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Kazidenov, Daniyar, Sagyn Omirbekov e Yerlan Amanbek. "Optimal Time-Step for Coupled CFD-DEM Model in Sand Production". In Computational Science and Its Applications – ICCSA 2023 Workshops, 116–30. Cham: Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-37111-0_9.
Testo completoAbstract (sommario):
AbstractThe coupled Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) is a useful tool for modeling the dynamics of sand production that occurs in oil and gas reservoirs. To perform accurate, physically relevant and efficient calculations, the optimal size of the simulation time-step should be selected. In this study, we investigate the selection of an appropriate time-step interval between CFD and DEM models in sand production simulations. The CPU time, speedup and root mean squared relative error of the obtained results are examined to compare the sand production phenomenon at different coupling numbers. Most of the results including the final sand production rate, bond number and bond ratio indicate that the simulations with coupling numbers of N = 10 and N = 100 produce more accurate results. Moreover, these outcomes demonstrate significant improvements in terms of acceleration of the modeling process.
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Sarkar, Avik, Brian Shoemaker, Pankaj Doshi, Mary T. am Ende, Dalibor Jajcevic, Peter Böhling, Peter Toson, Matej Zadravec e Johannes G. Khinast. "MULTISCALE MODELING OF A PHARMACEUTICAL FLUID BED COATING PROCESS USING CFD/DEM AND POPULATION BALANCE MODELS TO PREDICT COATING UNIFORMITY". In Chemical Engineering in the Pharmaceutical Industry, 419–50. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2019. http://dx.doi.org/10.1002/9781119600800.ch67.
Testo completo
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Wu, C. Y., e Y. Guo. "Enhancing the Capacity of DEM/CFD with an Immersed Boundary Method". In Discrete Element Modelling of Particulate Media, 10–20. The Royal Society of Chemistry, 2012. http://dx.doi.org/10.1039/bk9781849733601-00010.
Testo completoAbstract (sommario):
The coupled Discrete Element Method with Computational Fluid Dynamics (DEM/CFD) is a numerical technique for modelling fluid-solid particle flows, in which the motion of particles is modeled using DEM and that of fluid is solved using CFD. The interaction between the fluid and particles is approximated by an empirical correlation for the drag force. In this study, an immersed boundary method (IBM) is incorporated into DEM/CFD in order to model complex fluid-solid particle flows involving large objects and moving arbitrary shaped boundaries. The modified DEM/CFD is verified by comparing the numerical simulations with the experimental observation of the separation of binary mixtures in a vibrated bed. Its capacity is demonstrated with two case studies: i) fluidisation with a large immersed inclusion and ii) roll compaction in the presence of air. It is shown that the capacity of DEM/CFD is significantly enhanced with IBM and it can be used to simulate a range of particulate flows consisting of fluids and particles with large objects, complex and/or moving boundaries.
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Qiu, L., e C. Y. Wu. "Gravitational Sedimentation and Separation of Particles in a Liquid: a 3D DEM/CFD Study". In Discrete Element Modelling of Particulate Media, 30–38. The Royal Society of Chemistry, 2012. http://dx.doi.org/10.1039/bk9781849733601-00030.
Testo completoAbstract (sommario):
This paper presents a numerical investigation of sedimentation and separation of particles in liquids using a modified discrete element method coupled with computational fluid dynamics (DEM/CFD). In the present DEM/CFD, a weakly compressible fluid model is incorporated to model continuum carrier (liquid) phases, while a soft-sphere based DEM is used to model discrete particles. The key advantage of DEM over continuum methods is that it can be used to analyze sedimentation behaviour at the particle level and to model explicitly particle–particle and particle–wall collisions. Using the modified DEM/CFD, computational simulations of settling of spherical particles in a container fully filled with water have been conducted to examine effects of particle size, particle density, particle concentration and fluid viscosity on gravitational sedimentation of particles. A three dimensional numerical simulation of stratification and particle segregation in a liquid is also performed. It has been demonstrated that the modified DEM/CFD is a robust numerical technique for analyzing complex sedimentation and separation process of particles in liquids in 3D.
5
J.K. Wood, Robert, e Alexander D.C. Cook. "Erosion-Corrosion in Pipe Flows of Particle-Laden Liquids". In Slurry Technology - New Advances [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.107231.
Testo completoAbstract (sommario):
The transmission of particle-bearing liquids in pipes has motivated continuing research into erosion mechanisms and the distribution of erosion rates over wetted surfaces. This chapter covers these initiatives with particular reference to erosion-corrosion modelling within bends and straight sections of cylindrical pipes manufactured in a variety of materials and transporting a variety of liquids. Erosion-corrosion modelling techniques such as submerged slurry jets and rotating cylinder electrodes have been used to study factors influencing material degradation. Improvements in computational fluid dynamics (CFD), such as the development of a moving deforming mesh (MDM) have improved the accuracy of CFD models in predicting pipe wall erosion rates. Combined discrete phase tracking approaches such as the CFD-DPM-DEM (discrete phase-discrete element model) have helped improve computational efficiency. Wall impact erosion models are calibrated using laboratory scale tests. Validation of CFD models using full-scale test data is rare, meaning their accuracy is still largely unreported. Material testing has helped to identify the resilience of prospective pipeline materials to erosion-corrosion, while modifications to internal geometry and pipe section have shown potential to improve erosion-corrosion resistance.
6
Yu, Xiao, Sivaramakrishnan Balachandar, Jarrell Smith e Andrew J. Manning. "Flocculation Dynamics of Cohesive Sediment in Turbulent Flows Using CFD-DEM Approach". In Sediment Transport Research - Further Recent Advances [Working Title]. IntechOpen, 2024. http://dx.doi.org/10.5772/intechopen.1005171.
Testo completoAbstract (sommario):
Two-phase computational fluid dynamics - discrete element method (CFD-DEM) framework has gained attention in cohesive sediment transport due to its capability of resolving particle-particle interactions and capturing the time evolution of individual flocs and hence the flocculation dynamics of cohesive sediment in turbulent flows. For cohesive sediments of size smaller than the Kolmogorov length scale, the point-particle approach is commonly used, in which the flow around particles is not fully resolved, and the hydrodynamic force on particles is parameterized by the drag law. The accuracy of floc dynamics, aggregation, breakup, and reshaping therefore strongly depends on force parameterization of individual point-particles that make up the floc. In this chapter, we review recent advances in the state-of-art two-phase CFD-DEM model approach on cohesive sediment transport and make recommendation for future research.
7
Di Renzo, A., e F. P. Di Maio. "From Single Particle Drag Force to Segregation in Fluidised Beds". In Discrete Element Modelling of Particulate Media, 3–9. The Royal Society of Chemistry, 2012. http://dx.doi.org/10.1039/bk9781849733601-00003.
Testo completoAbstract (sommario):
Discrete Element Modelling has been successfully applied in combination with fluid flow solvers (CFD) to tackle important multi-phase process engineering problems. However, until recently most of the DEM-CFD studies have dealt with monodisperse particulate systems. The reason for that is that DEM requires knowledge of the force exerted by the flowing fluid on each particle. While numerous expressions are available for homogenous systems, the presence of size polydispersion or the presence of solids mixtures complicate particle-level formulations of the drag force considerably and a general model is still lacking. In the present contribution a drag force model for polydisperse system is introduced and discussed. The expression was originally proposed in the literature on the basis of lattice-Boltzmann simulation results for flow through random polydisperse systems. However, its theoretical foundations were not fully recognised. The proposed formula requires the introduction of an average diameter, whose definition will be proved to be rigorously derivable provided that appropriate consistency constraints are considered. No other fitting or adjustable parameters are involved. In the case of a binary mixture of differently sized particles the resulting drag force is shown to depend both on size ratio and local volume fraction of the solids. Such precious particle-level information is then shown to be extendable to the macroscopic scale with attractive potentialities. On this basis, solution to the (open) problem of the segregation direction in a gas-fluidized bed of binary solids endowed with contrasting density and size differences will be suggested.
8
Tang, Jun, Bing Zhou, Bin Yi, Yadong Wen, Xianqing Fu, Yue Liu, Yanchao Yin e Wenqiang Lin. "Numerical Simulation of Separating Tobacco Leaves from Stems Based on DEM-CFD Coupling". In Advances in Transdisciplinary Engineering. IOS Press, 2023. http://dx.doi.org/10.3233/atde230993.
Testo completoAbstract (sommario):
To enhance the separation efficiency in the separator during the process of separating tobacco leaves from the stems, it is necessary to study how the airflow affects the motion of the tobacco in the separation chamber. Therefore, a DEM-CFD coupling model is established to simulate the interaction between the airflow and the mixed tobacco leaves and stems. Different inlet wind speeds, between 7.5 m/s–15 m/s are set to study the effect of inlet velocity on the stems separation efficiency. The results show that the inlet wind speed of 12.5 m/s–15 m/s can lead to a better separation effect, giving a 76% destemming rate with only 4% tobacco leaves waste.
9
Tang, Jun, Bin Yi, Wenqiang Lin, Yadong Wen, Chengrong Xin, Yue Liu, YanChao Yin e Bing Zhou. "A Coupled CFD-DEM Simulation for Optimization of Tobacco Stems Separation Efficiency in a Cylindrical Separator". In Advances in Transdisciplinary Engineering. IOS Press, 2023. http://dx.doi.org/10.3233/atde230989.
Testo completoAbstract (sommario):
To remove the stem from the cut tobacco and improve the quality of the cigarettes, a second winnowing process is added to the primary separator to reduce the loss of the tobacco leaves. The separation effect of the high stem proportional tobacco stream coming from the primary winnowing process was simulated based on the CFD-DEM coupling method. Three different lengths of tobacco models were established to give a more realistic tobacco size distribution. The velocity contour in the circular chamber of the second separator with four different inlet speeds is illustrated to analyze the fluid field characteristic. The proportion of leaves and stems in the upper and lower outlets after winnowing was calculated to obtain separation efficiency. The results suggest a better separation effect with the inlet speed of 7.5 m/s at tobacco stream feed rates of 500 kg/h and 1000 kg/h.
10
Tang, Jun, Wenqiang Lin, Bing Zhou, Banghua He, Shilong Xu, Yue Liu, Yanchao Yin e Bin Yi. "Numerical Study of the Separation Effect of Tobacco Stem Separator with Different Chamber Shapes". In Advances in Transdisciplinary Engineering. IOS Press, 2023. http://dx.doi.org/10.3233/atde230990.
Testo completoAbstract (sommario):
To minimize the containing of the stem in the cut tobacco and thus enhance the quality of the cigarettes, the separator used in the winnowing process needs well designed. The separation efficiency of the winnowing process of cut tobacco is affected by many parameters, such as the separator geometry, airflow speed, tobacco feed rate, etc. Among those, the separator geometry should be pre-designed to coordinate with the working airflow speed and tobacco feed rate. This article studies the effect of different chamber shapes of the separator on the separation efficiency of tobacco leaves and stems under various conditions with the same airflow speed. A CFD-DEM coupling model is established to simulate the tobacco motion in the chamber. The contour of velocity and separation rate of tobacco leaves and stems with square and circular chamber is compared. The results indicate that the chamber shapes can affect the fluid field characteristic and hence the separation effect under some airflow speed, the inlet airflow speed should be adjusted to improve the separation rate and achieve better efficiency.
Atti di convegni sul tema "Modèle CFD-DEM"
1
Maramizonouz, Sadaf, e Sadegh Nadimi. "Accounting for Particle Morphology in CFD-DEM Modelling". In UK Association for Computational Mechanics Conference 2024. Durham University, 2024. http://dx.doi.org/10.62512/conf.ukacm2024.074.
Testo completoAbstract (sommario):
In this study, the drag force acting on real irregular particles with various morphologies belonging to the four shape categories of the Zingg chart is estimated using the empirical models proposed in literature and the results are compared to the drag force obtained through computational fluid dynamics (CFD). Then, the chosen drag models are utilised to numerically simulate the flow of irregular particles through air along a cylindrical pipe, their exit at the nozzle, and their entrainment at a certain spot. The dynamics of the particulate material is simulated using discrete element method (DEM) modelling that is one-way coupled to CFD simulations via the drag force exerted on the particles. It is observed that particle morphology significantly influences the particle flow dynamics.
2
Elghannay, Husam, Kuahai Yu e Danesh Tafti. "On the Improvement of CFD-DEM Coarse Graining Predictions". In ASME 2016 Fluids Engineering Division Summer Meeting collocated with the ASME 2016 Heat Transfer Summer Conference and the ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/fedsm2016-7805.
Testo completoAbstract (sommario):
Discrete Element Method (DEM) coupled to Computational Fluid Mechanics (CFD) is a powerful tool for simulating complex multiphase flows. The cost of this Eulerian-Lagrangian description, however, increases with the increase of the number of particles ∼O(Np) which limit its use in natural and industrial scale systems. Efforts to reduce the cost of CFD-DEM capability include reducing the total number of simulated particles by lumping them in larger size representative particles (RP Model). The scaled Representative Particle simulations are less compute intensive compared to the more expensive high fidelity un-scaled/resolved simulations. The prediction accuracy of the RP model, however, decreases as larger scaling factors are used. In the current work, we study the possibility of getting improved results from RP model by using two different techniques. First attempts will be made to identify reasons for reduction in RP model prediction accuracy, then different techniques for improvement of RP model are suggested and tested. In the second part, the ability of the co-kriging surrogate model to improve CFD-DEM predictions by combining many reduced-order RP model simulations with a few high-fidelity unscaled calculations is tested. Appropriate systems are selected to evaluate each method.
3
Bernard, Manuel, Anthony Wachs e Eric Climent. "Multiscale Approach for Particulate Flows, Application to Fluidized Beds". In ASME 2014 4th Joint US-European Fluids Engineering Division Summer Meeting collocated with the ASME 2014 12th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/fedsm2014-22020.
Testo completoAbstract (sommario):
In this paper, a discrete element method (DEM) coupled with computational fluid dynamics (CFD) and a distributed Lagrange multiplier - fictitious domain method (DLM-FD) are used is order to model three-dimensional fluidized beds. Particle-particle and wall-particle contacts are handled thanks to a soft sphere model. For the DEM-CFD model, also called Euler-Lagrange model, fluid dynamics variables are locally averaged and solved on a grid larger than the particle size whereas for the DLM-FD grid cells are around 20 times smaller than the particle characteristic length. The aim of this work is to extract information from DLM-FD simulations to improve the correlations used in the DEM-CFD model. First, particles and fluid equations are presented for the Euler-Lagrange model. Then, fluid-particle interaction is detailed. Eventually, we present preliminary simulations and results with both models in a 3D fluidized bed configuration.
4
Studeník, Ondřej, Martin Kotouč Šourek e Martin Isoz. "Octree-Generated Virtual Mesh for Improved Contact Resolution in CFD-Dem Coupling". In Topical Problems of Fluid Mechanics 2022. Institute of Thermomechanics of the Czech Academy of Sciences, 2022. http://dx.doi.org/10.14311/tpfm.2022.021.
Testo completoAbstract (sommario):
The present work is focused on improving the efficiency of a computational fluid dynamics (CFD) – discrete element method (DEM) solver allowing for computations with non-spherical solids. In general, the combination of CFD and DEM allows for simulations of freely moving solid particles within a computational domain containing fluid. The standard approach of CFD-DEM solvers is to approximate solid bodies by spheres, the geometry of which can be fully defined via its radius and center position. Consequently, the standard DEM contact models are based on an overlap depth between particles, which can be easily evaluated for a sphere-sphere contact. However, for a contact between two non-spherical particles, the overlap depth cannot be used and has to be replaced by the more general overlap volume. The precision of the overlap volume computation is (i) crucial for the correct evaluation of contact forces, and (ii) directly dependent on the computational mesh resolution. Still, the contact volume evaluation in DEM for arbitrarily shaped bodies is usually by at least one order of magnitude more demanding on the mesh resolution than the CFD. In order to improve the computational efficiency of our CFD-DEM solver, we introduce the concept of an OCTREEbased virtual mesh, in which the DEM spatial discretization is adaptively refined while the CFD mesh remains unchanged.
5
Badhan, Antara, V. M. Krushnarao Kotteda e Vinod Kumar. "CFD DEM Analysis of a Dry Powder Inhaler". In ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/ajkfluids2019-4771.
Testo completoAbstract (sommario):
Abstract Dry powder inhalers (DPIs), used as a means for pulmonary drug delivery, typically contain a combination of active pharmaceutical ingredient (API) and significantly larger carrier particles. The micro-sized drug particles — which have a strong propensity to aggregate and poor aerosolization performance — mixed with significantly large carrier particles that are unable to penetrate the mouth-throat region to deagglomerate and entrain the smaller API particles in the inhaled airflow. The performance of a DPI, therefore, depends on entrainment the carrier-API combination particles and the time and thoroughness of the deagglomeration of the individual API particles from the carrier particles. Since DPI particle transport is significantly affected by particle-particle interactions, very different particles sizes and shapes, various forces including electrostatic and van der Waals forces, they present significant challenges to Computational Fluid Dynamics (CFD) modelers to model regional lung deposition from a DPI. In the current work, we present a novel high fidelity CFD discrete element modeling (CFD-DEM) and sensitivity analysis framework for predicting the transport of DPI carrier and API particles. The work integrates exascale capable CFD-DEM and sensitivity analysis capabilities by leveraging the Department of Energy (DOE) laboratories libraries: Multiphase Flow Interface Flow Exchange (MFiX) for CFD-DEM, and Trilinos for leading-edge portable/scalable linear algebra. We carried out a sensitivity analysis of various formulation properties and their effects on particle size distribution with Dakota, an open source software designed to exploit High-Performance Computing (HPC) capabilities of a massively parallel supercomputer. We developed wrappers to exchange information among these state-of-the-art tools for DPI.
6
Agrawal, Madhusuden, Ahmadreza Haghnegahdar e Rahul Bharadwaj. "Improved Prediction of Sand Erosion by Accurate Particle Shape Representation in CFD-DEM Modelling". In SPE Annual Technical Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/206122-ms.
Testo completoAbstract (sommario):
Abstract Predicting accurate erosion rate due to sand particles in oil and gas production is important for maintaining safe and reliable operations while maximizing output efficiency. Computational Fluid Dynamic (CFD) is a powerful tool for erosion prediction as it provides detailed erosion pattern in complex geometry. In an effort to improve accuracy of erosion prediction, this paper proposes an algorithm to accurately represent particle shape in CFD erosion simulation through coupling with Discrete Element Method (DEM) for non-spherical shape particles. The fluid motions are predicted by CFD and the particle movements (including particle-particle and particle-wall collisions) and fluid-particle interaction are calculated using DEM. It is widely known that sand particles are of finite volume with a non-spherical shape, accurate representation of sand particles is important in CFD modelling for accurate prediction of erosion rate. Traditional CFD approach usages lagrangian tracking of sand particles through Discrete Phase Model (DPM), where a particle is assumed as a point mass for the calculation of trajectory and particle-wall interaction. Particle impact velocity and impact angle are important parameter in determining erosion. Assumption of point mass in DPM approach, will not capture particle-wall interaction accurately especially when particles are of non-spherical in shape. In additional, DPM approach ignores particle-particle interactions. This can adversary affect the accuracy of erosion predictions. Integrating non-spherical DEM collision algorithm with CFD erosion simulation, will overcome these limitations and improve erosion predictions. Benefits of this CFD-DEM erosion modelling was demonstrated for gas-solid flow in a 2" pipework which consists of out-of-plane elbows in series and blind-tees. Experimental dataset [1] for erosion pattern on each elbow was used to validate CFD predictions. Three different erosion CFD simulations were performed, traditional DPM based CFD simulation, CFD-DEM simulation for spherical shape particles and CFD-DEM simulation for non-spherical shape particles. CFD-DEM coupled simulations clearly show an improvement on erosion predictions compared to DPM based CFD simulation. Effect of non-spherical shape on rebound angle during particle-wall collision is captured accurately in CFD-DEM simulation. CFD-DEM simulation using non-spherical particle, was able to predict erosion pattern closer to experimental observations. This paper will demonstrate an increase in accuracy of sand erosion prediction by integrating DEM collision algorithm in CFD modelling. The prediction results of elbow erosion subject to a condition of dilute gas-particle flow are validated against experimental data. Improved prediction of erosion risk will increase the safety and reliability of oil & gas operations, while maximizing output efficiency.
7
Weaver, Dustin, e Sanja Miskovic. "Analysis of Coupled CFD-DEM Simulations in Dense Particle-Laden Turbulent Jet Flow". In ASME 2020 Fluids Engineering Division Summer Meeting collocated with the ASME 2020 Heat Transfer Summer Conference and the ASME 2020 18th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/fedsm2020-20274.
Testo completoAbstract (sommario):
Abstract In this paper, coupled CFD-DEM simulations of dense particle-laden jet flow are performed using CFDEM® coupling interface that couples LAMMPS-based LIGGGHTS® DEM engine with OpenFOAM CFD framework. Suspensions of mono-sized spherical glass particles with 80 microns diameter and a mass loading of 0.23 and 0.86 are considered. Three different CFD meshes are used with an average mesh resolution dimension of 3.06, 2.67, and 1.86 particle diameters and it is determined that mesh resolution does not change results for void fraction calculation (using the divided model) of the CFD-DEM equations. Samples of particle flux are taken at 0.1, 10, and 20 nozzle diameters along the axial direction of the jet region. The numerical results for particle flux are compared with a well cited experimental data found in literature. The CFD-DEM simulations in turbulent jet flow are found to be highly sensitive to initial particle velocity inputs but the experimental data provide sufficient information to produce comparable results.
8
Wrenger, Hendrik, Bruno Sainte-Rose, Christoph Goniva e Renan Hilbert. "Plastic Accumulation in Front of a Plate in Cross Flow: Model Scale Test and CFD-DEM Modelling". In ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/omae2019-96095.
Testo completoAbstract (sommario):
Abstract Results of a flume experiment and numerical model of plastic accumulation in front of a plate are presented. The single phase CFD-DEM model formed a successful benchmark case to model plastic accumulation inside an ocean cleanup system. A fixed wooden plate was placed in a steady cross flow and plastic was released upstream of it. We recorded the evolution of the plastic accumulation profiles under slowly increasing plastic load. Experimental parameters were the flow velocity, draft of the plate (varying the plate Froude number) as well as three different types of plastic particles. The accumulation of oil in front of barriers and parallels to the phenomena of plastic accumulation were reviewed. As a second part of the project we used the open source CFD-DEM code CFDEM® to reproduce the flume experiment. It couples the discrete element method (DEM) software LIGGGHTS® and the open source computational fluid dynamics (CFD) software OpenFOAM®. A linear relationship of the relative depth of the accumulation with the Froude number of the plate was found for a given type of particle and reproduced in the numerical model. We identified limitations of the experimental setup, calibration experiments and the single phase CFD-DEM approach and outlined the steps for further research.
9
Lu, Teng-Chao, e Zao-Jian Zou. "Numerical Simulation of Ice-Wave Interaction by Coupling DEM-CFD". In ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/omae2019-95105.
Testo completoAbstract (sommario):
Abstract The motions of ice floes in linear waves were simulated by coupling Discrete Element Method (DEM) and Computational Fluid Dynamics (CFD). The interactions between ice floes are investigated by DEM. The hydrodynamics of ice floes, mainly including the drag force and the buoyancy, are calculated by CFD. In the simulation, the ice floes are treated as discrete elements, and the contact forces between ice floes are determined by the Hertz-Mindlin (no-slip) contact model. The shape of ice floes is an approximate square composed of a number of spherical faces, which can reduce the computation cost. The waves are treated as First Order Airy wave, which is linear in nature and applied to small amplitude waves in shallow liquid depth ranges. The volume of fluid (VOF) method was adopted to capture the free surface. The simulation results are in agreement with the actual situation to a certain extent.
10
Alihosseini, Maryam, e Paul Uwe Thamsen. "On Scouring Efficiency of Flush Waves in Sewers: A Numerical and Experimental Study". In ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/ajkfluids2019-4615.
Testo completoAbstract (sommario):
Abstract In sewer sediment management, the removal of depositions using hydraulic flushing gates has recently gotten great attention. Despite numerous investigations, the complex process of sediment transport under flushing waves is not yet well understood. The present work aims to calibrate and validate a coupled computational fluid dynamics and discrete element method (CFD-DEM) to study the fluid-sediment interaction in sewers. The CFD part of the simulation was carried out in the software Ansys Fluent which is two-way coupled to the DEM software EDEM. The multiphase model volume of fluid (VOF) was used to simulate the flushing wave, while the sediments were handled as DEM particles using the discrete phase model (DPM). To validate the 3D model, experimental work has been performed in a circular laboratory pipe with sand and gravel of different size distributions. A construction of a sluice gate was installed to realize the flushing event, which is similar to a dam-break wave. The evolution of the sediment bed and the scouring efficiency of the waves were examined under different flushing conditions. The results showed that the CFD-DEM method could be used to investigate the performance of flushing devices and various features of sediment transport which are not easy to obtain in the laboratory or field.
Rapporti di organizzazioni sul tema "Modèle CFD-DEM"
1
Pullammanappallil, Pratap, Haim Kalman e Jennifer Curtis. Investigation of particulate flow behavior in a continuous, high solids, leach-bed biogasification system. United States Department of Agriculture, gennaio 2015. http://dx.doi.org/10.32747/2015.7600038.bard.
Testo completoAbstract (sommario):
Recent concerns regarding global warming and energy security have accelerated research and developmental efforts to produce biofuels from agricultural and forestry residues, and energy crops. Anaerobic digestion is a promising process for producing biogas-biofuel from biomass feedstocks. However, there is a need for new reactor designs and operating considerations to process fibrous biomass feedstocks. In this research project, the multiphase flow behavior of biomass particles was investigated. The objective was accomplished through both simulation and experimentation. The simulations included both particle-level and bulk flow simulations. Successful computational fluid dynamics (CFD) simulation of multiphase flow in the digester is dependent on the accuracy of constitutive models which describe (1) the particle phase stress due to particle interactions, (2) the particle phase dissipation due to inelastic interactions between particles and (3) the drag force between the fibres and the digester fluid. Discrete Element Method (DEM) simulations of Homogeneous Cooling Systems (HCS) were used to develop a particle phase dissipation rate model for non-spherical particle systems that was incorporated in a two-fluid CFDmultiphase flow model framework. Two types of frictionless, elongated particle models were compared in the HCS simulations: glued-sphere and true cylinder. A new model for drag for elongated fibres was developed which depends on Reynolds number, solids fraction, and fibre aspect ratio. Schulze shear test results could be used to calibrate particle-particle friction for DEM simulations. Several experimental measurements were taken for biomass particles like olive pulp, orange peels, wheat straw, semolina, and wheat grains. Using a compression tester, the breakage force, breakage energy, yield force, elastic stiffness and Young’s modulus were measured. Measurements were made in a shear tester to determine unconfined yield stress, major principal stress, effective angle of internal friction and internal friction angle. A liquid fludized bed system was used to determine critical velocity of fluidization for these materials. Transport measurements for pneumatic conveying were also assessed. Anaerobic digestion experiments were conducted using orange peel waste, olive pulp and wheat straw. Orange peel waste and olive pulp could be anaerobically digested to produce high methane yields. Wheat straw was not digestible. In a packed bed reactor, anaerobic digestion was not initiated above bulk densities of 100 kg/m³ for peel waste and 75 kg/m³ for olive pulp. Interestingly, after the digestion has been initiated and balanced methanogenesis established, the decomposing biomass could be packed to higher densities and successfully digested. These observations provided useful insights for high throughput reactor designs. Another outcome from this project was the development of low cost devices to measure methane content of biogas for off-line (US$37), field (US$50), and online (US$107) applications.