Made available in DSpace on 2014-12-17T15:03:25Z (GMT). No. of bitstreams: 1 JoseEM_DISSERT_1-90.pdf: 4896611 bytes, checksum: 9ac9fa14f37adc67a0417c2b8781cf4e (MD5) Previous issue date: 2010-12-28 / Digital Elevation Models (DEM) are numerical representations of a portion of the earth surface. Among several factors which affect the quality of a DEM, it should be emphasized the attention on the input data and the choice of the interpolating algorithm. On the other hand, several numerical models are used nowadays to characterize nearshore hydrodynamics and morphological changes in coastal areas, whose validation is based on field data collection. Independent on the complexity of the physical processes which are modeled, little attention has been given to the intrinsic bathymetric interpolation built within the numerical models of the specific application. Therefore, this study aims to investigate and to quantify the influence of the bathymetry, as obtained by a DEM, on the hydrodynamic circulation model at a coastal stretch, off the coast of the State of Rio Grande do Norte, Northeast Brazil. This coastal region is characterized by strong hydrodynamic and littoral processes, resulting in a very dynamic morphology with shallow coastal bathymetry. Important economic activities, such as oil exploitation and production, fisheries, salt ponds, shrimp farms and tourism, also bring impacts upon the local ecosystems and influence themselves the local hydrodynamics. This fact makes the region one of the most important for the development of the State, but also enhances the possibility of serious environmental accidents. As a hydrodynamic model, SisBaHiA? - Environmental Hydrodynamics System ( Sistema B?sico de Hidrodin?mica Ambiental ) was chosen, for it has been successfully employed at several locations along the Brazilian coast. This model was developed at the Coastal and Oceanographical Engineering Group of the Ocean Engineering Program at the Federal University of Rio de Janeiro. Several interpolating methods were tested for the construction of the DEM, namely Natural Neighbor, Kriging, Triangulation with Linear Interpolation, Inverse Distance to a Power, Nearest Neighbor, and Minimum Curvature, all implemented within the software Surfer?. The bathymetry which was used as reference for the DEM was obtained from nautical charts provided by the Brazilian Hydrographic Service of the Brazilian Navy and from a field survey conducted in 2005. Changes in flow velocity and free surface elevation were evaluated under three aspects: a spatial vision along three profiles perpendicular to the coast and one profile longitudinal to the coast as shown; a temporal vision from three central nodes of the grid during 30 days; a hodograph analysis of components of speed in U and V, by different tidal cycles. Small, but negligible, variations in sea surface elevation were identified. However, the differences in flow and direction of velocities were significant, depending on the DEM / Os modelos digitais de terreno (MDT) consistem na representa??o matem?tica computacional da distribui??o de um fen?meno espacial que ocorre dentro de uma regi?o da superf?cie terrestre. A qualidade da representa??o do MDT est? influenciada, dentre outros fatores, pela origem do dado e pelo algoritmo interpolador utilizado. A caracteriza??o da circula??o hidrodin?mica ? um dos estudos com apelo ambiental que se utiliza dos MDTs como dado de entrada e, independentemente da complexidade dos processos representados nos modelos num?ricos, pode ter a qualidade de seus resultados dependente da capacidade de reprodu??o do MDT usado para representar a batimetria da ?rea de interesse. Sendo assim, o objetivo deste estudo ? avaliar a influ?ncia de batimetrias obtidas de diversos MDTs, nos padr?es de circula??o hidrodin?mica via modelagem num?rica. Para tanto, considerou-se os dados referentes ? regi?o costeira do nordeste do Brasil, correspondente ao litoral setentrional do estado do Rio Grande do Norte, frontal aos munic?pios de Macau, Guamar? e Galinhos. Essa regi?o se caracteriza pela forte presen?a de processos f?sicos costeiros, com batimetria rasa e complexas fei??es de fundo. A presen?a intensa de atividades petrol?feras faz da regi?o uma das mais importantes para o desenvolvimento socioecon?mico do estado, mas, por outro lado, potencializa a possibilidade de acidentes ambientais de grandes e graves propor??es. O modelo de circula??o hidrodin?mica utilizado foi o 2DH, que faz parte do Sistema de Hidrodin?mica Ambiental, chamado SisBaHiA?, desenvolvido pela ?rea de Engenharia Costeira e Oceanogr?fica do Programa de Engenharia Oce?nica da COPPE/UFRJ. Os interpoladores avaliados foram Vizinho Natural, Krigagem, Triangula??o Irregular Linear, Inverso da Dist?ncia, Vizinho mais Pr?ximo, M?nima Curvatura, Fun??o de Base Radial, Polin?mio Local, Regress?o Polinomial, M?dia M?vel, M?trica de Dados e M?todo de Shepard Modificado, implementados no software comercial Surfer? para a gera??o dos MDTs. Os dados batim?tricos, que serviram como base para a constru??o dos MDTs, s?o oriundos de campanha de campo e de cartas n?uticas. Os resultados das modelagens foram analisados pelas avalia??es dos campos de velocidade e eleva??o, sob tr?s aspectos: uma vis?o espacial dos resultados, atrav?s da an?lise de tr?s perfis perpendiculares ? linha de costa e um perfil transversal ? linha de costa; uma vis?o temporal dos resultados, ao longo do per?odo de 30 dias, a partir de tr?s n?s centrais da malha; e finalmente uma an?lise hodogr?fica das componentes de velocidade em U e V, em diferentes ciclos de mar?s. Foram verificadas varia??es pouco significativas nos campos de eleva??es, podendo as mesmas serem desprezadas, por?m no que diz respeito aos campos de velocidade e dire??es de fluxo, notam-se varia??es associadas aos MDTs utilizados, uma vez que todas as condicionantes hidrodin?micas foram mantidas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Since the industrial processes efficiency depends on the granular flow regime established under given operating conditions on the rotary drum, the ability to predict the particle motion inside this equipment, including the particle properties effect, is of primary importance. So, in this work an experimental and numerical study was carried out in order to investigate: the transition phenomenon between different flow regimes, the mixture and segregation phenomenon and the particle dynamic behavior inside an unbaffled rotary drum, under different operating conditions, using particles of different physical properties. A modification of the Blumberg and Schlünder model equation for rolling-cascading transition was proposed by the introduction of the particle shape effect, represented here by the sphericity. It was observed, for the first time, the hysteresis phenomenon in the transition between cataractingcentrifuging regimes which was shown to be dependent on the physical properties of the particles such as sphericity, density and particle-wall friction coefficient. A new expression relating the critical rotation speed for centrifuging as a function of the filling degree, which takes into consideration the particle properties and the hysteresis effects, was proposed. Regarding the segregation phenomenon, radial segregation due to particle diameter and density differences was observed in all systems studied after a few drum rotations. Size induced axial segregation (banding) was observed, as expected. However density differences alone did not induce axial segregation. As regards the numerical investigation, two different approaches were used for the granular flow prediction inside a rotary drum: Eulerian and Lagrangian. For the Eulerian approach, the results indicated that the kinetic model, which has been successfully applied in many dilute granular flow simulations, may also be applied in the dense granular flow treatment present in rotary drums. It was also observed that, the drag force can be neglected in the case of a rotating drum operated in the rolling regime where there is no fluid entering or leaving the system. Taking the computational efforts into account, this force can be set to zero in the entire calculation domain. For the Lagrangian model calibration, a sensitivity analysis of the numerical dynamic angle of repose due to variations in the friccional coefficient (μf) and the damping ratio (β), both varying from 0.149 to 0.701, was assessed using a Central Composite Design. The smallest deviation from the experimental data when using rice grains was obtained in the simulation whose parameters values were μf = 0.425 and β = 0.149 with an error of about 2.9%. As regards the glass beads, the smallest deviation between experiment and simulation was found using a friction coefficient μf = 0.701 and damping ratio β = 0.425 with an error of about 3.4%. For the case of the rotary drum using rice grains, which are characterized by irregular shapes, the calibrated model was affected by neither the filling degree nor the drum rotation speed. On the other hand, in the case of rounded particles (glass beads), the Lagrangian model parameters should be calibrated to specific conditions of rotation speed and filling degree and cannot be generalized. / A eficiência dos processos industriais desenvolvidos em um tambor rotatório depende da forma como as partículas ou grãos movimentam-se em seu interior. O entendimento dos principais mecanismos que regem estes movimentos e a capacidade de prevê-los através de técnicas de modelagem computacional tornam-se de importância primordial para questões de operação, projeto e otimização. Neste sentido, este trabalho teve como foco a aplicação de metodologias experimentais e numéricas com o intuito de estudar: 1) o fenômeno de transição entre os diferentes regimes de escoamento; 2) mistura e segregação; 3) dinâmica de partículas em um tambor rotatório sob diferentes condições operacionais utilizando partículas com diferentes propriedades físicas. Foi proposta uma nova expressão para a velocidade crítica de rotação para centrifugação função, além do grau de preenchimento do tambor, das propriedades físicas das partículas. Uma modificação no modelo desenvolvido por Blumberg e Schlünder (1996) para a transição rolamento-cascateamento através da inclusão do efeito da forma das partículas foi também introduzida. Observou-se, pela primeira vez na literatura, o fenômeno de histerese quando da transição entre os regimes catarateamento-centrifugação o qual se mostrou dependente das propriedades físicas dos materiais particulados tais como: esfericidade, massa específica e coeficiente de atrito partícula-parede. Foi possível a realização de uma investigação, tanto quantitativa quanto qualitativa, acerca dos efeitos das diferenças de diâmetro, massa específica e da condição inicial do material no interior do tambor rotatório sobre o fenômeno de segregação radial e axial (mistura binária). O fenômeno da segregação axial foi observado apenas quando da diferença de diâmetros entre as partículas. A diferença tão somente da massa específica, independente das condições de velocidade de rotação e grau de preenchimento, não causou segregação axial. No que diz respeito à abordagem numérica, duas diferentes aproximações para a previsão do escoamento granular no interior do tambor foram utilizadas: Euleriana e Lagrangeana. Comparações entre os perfis radiais de velocidade de sólidos experimentais e simulados através do modelo Euleriano mostraram que o modelo cinético-colisional, o qual tem sido aplicado com sucesso em muitas simulações de escoamento granulares diluídos pode, também, ser aplicado no tratamento de um escoamento granular denso presente em tambores rotatórios. Neste caso, observou-se também que a força de arrasto ou resistiva fluido-sólido pode ser negligenciada no caso de um tambor rotatório operando no regime de rolamento, onde não há entrada ou saída de fluido do sistema. No processo de calibração do modelo Lagrangeano através de um Planejamento Composto Central, os valores determinados dos parâmetros coeficiente de atrito (μp) e razão de amortecimento (ζ) para o arroz foram de, respectivamente, 0,425 e 0,149 (erro relativo de 2,9%), enquanto que para as esferas de vidro foram de 0,701 e 0,425 (erro relativo de 3,4%), respectivamente. Os parâmetros da modelagem Lagrangeana determinados para as partículas arredondadas (esferas de vidro) mostraram-se dependentes das condições operacionais. Já para as partículas irregulares (arroz), a calibração dos parâmetros através de um tambor em escala reduzida, mostrou-se adequada para o emprego na previsão do escoamento em tambores rotatórios em uma escala superior, podendo futuramente ser empregada em uma escala industrial. / Doutor em Engenharia Química

I dagens svenska samhälle har vi blivit allt mer mångkulturella och integration har därmed blivit en viktig fråga. Vi präglas av en mängd olika nationaliteter, etniska minoriteter samt olika kulturella bakgrunder. Därför är det viktigt för ett land som Sverige som anses vara demokratiskt att ha förståelse och respektera alla människor, oavsett vilken etnicitet och kulturell bakgrund en person har. Förståelse för varandra är oerhört viktigt eftersom alla som är en del av samhället inte skall känna ett utanförskap eller bli diskriminerade. Detta förekommer dock enligt en rad olika (författare och forskare) som har hävdat att den integrationspolitik som har förts i Sverige de senaste trettio åren har misslyckats. Därmed behöver det ske en förändring inom integrationspolitiken, ansvaret ligger på både den nuvarande borgerliga regeringen men lika väl invånarna i samhället. I detta projektarbete har jag analyserat olika rapporter utifrån Statens offentliga utredningar (SOU) för att på så sätt få en mer övergripande bild av hur integration förts i Sverige. Därtill belyser jag hur regeringspropositionerna ser ut gällande de mål och visioner, som den föregående regeringen, socialdemokraterna, hade för att skapa en god integrationspolitik.

While tribology involves the study of friction, wear, and lubrication of interacting surfaces, the tribosurfaces are the pair of surfaces in sliding contact with a fluid (or particulate) media between them. The ubiquitous nature of tribology is evident from the usage of its principles in all aspects of life, such as the friction promoting behavior of shoes on slippery water-lubricated walkways and tires on roadways to the wear of fingernails during filing or engine walls during operations. These tribosurface interfaces, due to the small length scales, are difficult to model for contact mechanics, fluid mechanics and particle dynamics, be it via theory, experiments or computations. Also, there is no simple constitutive law for a tribosurface with a particulate media. Thus, when trying to model such a tribosurface, there is a need to calibrate the particulate media against one or more property characterizing experiments. Such a calibrated media, which is the “virtual avatar” of the real particulate media, can then be used to provide predictions about its behavior in engineering applications. This thesis proposes and attempts to validate an approach that leverages experiments and modeling, which comprises of physics-based modeling and machine learning enabled surrogate modeling, to study particulate media in two key particle matrix industries: metal powder-bed additive manufacturing (in Part II), and energy resource rock drilling (in Part III). The physics-based modeling framework developed in this thesis is called the Particle-Surface Tribology Analysis Code (P-STAC) and has the physics of particle dynamics, fluid mechanics and particle-fluid-structure interaction. The Computational Particle Dynamics (CPD) is solved by using the industry standard Discrete Element Method (DEM) and the Computational Fluid Dynamics (CFD) is solved by using finite difference discretization scheme based on Chorin's projection method and staggered grids. Particle-structure interactions are accounted for by using a state-of-the art Particle Tessellated Surface Interaction Scheme and the fluid-structure interaction is accounted for by using the Immersed Boundary Method (IBM). Surrogate modeling is carried out using back propagation neural network. The tribosurface interactions encountered during the spreading step of the powder-bed additive manufacturing (AM) process which involve a sliding spreader (rolling and sliding for a roller) and particulate media consisting of metal AM powder, have been studied in Part II. To understand the constitutive behavior of metal AM powders, detailed rheometry experiments have been conducted in Chapter 5. CPD module of P-STAC is used to simulate the rheometry of an industry grade AM powder (100-250microns Ti-6Al-4V), to determine a calibrated virtual avatar of the real AM powder (Chapter 6). This monodispersed virtual avatar is used to perform virtual spreading on smooth and rough substrates in Chapter 7. The effect of polydispersity in DEM modeling is studied in Chapter 8. A polydispersed virtual avatar of the aforementioned AM powder has been observed to provide better validation against single layer spreading experiments than the monodispersed virtual avatar. This experimentally validated polydispersed virtual avatar has been used to perform a battery of spreading simulations covering the range of spreader speeds. Then a machine learning enabled surrogate model, using back propagation neural network, has been trained to study the spreading results generated by P-STAC and provide much more data by performing regression. This surrogate model is used to generate spreading process maps linking the 3D printer inputs of spreader speeds to spread layer properties of roughness and porosity. Such maps (Chapters 7 and 8) can be used by a 3D-printer technician to determine the spreader speed setting which corresponds to the desired spread layer properties and has the maximum spread throughout. The tribosurface interactions encountered during the drilling of energy resource rocks which involve a rotary and impacting contact of the drill bit with the rock formation in the presence of drilling fluids have been studied in Part III. This problem involves sliding surfaces with fluid (drilling mud) and particulate media (intact and drilled rock particles). Again, like the AM powder, the particulate media, viz. the rock formation being drilled into, does not have a simple and a well-defined constitutive law. An index test detailed in ASTM D 5731 can be used as a characterization test while trying to model a rock using bonded particle DEM. A model to generate weak concrete-like virtual rock which can be considered to be a mathematical representation of a sandstone has been introduced in Chapter 10. Benchtop drilling experiments have been carried out on two sandstones (Castlegate sandstone from the energy rich state of Texas and Crab Orchard sandstone from Tennessee) in Chapter 11. Virtual drilling has been carried out on the aforementioned weak concrete-like virtual rock. The rate of penetration (RoP) of the drill bit has been found to be directly proportional to the weight on bit (WoB). The drilling in dry conditions resulted in a higher RoP than the one which involved the use of water as the drilling fluid. P-SATC with the bonded DEM and CFD modules was able to predict both these findings but only qualitatively (Chapter 11)

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-07-28T12:46:53Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) tese_diogotc_final.pdf: 7303783 bytes, checksum: f9959e8bb63b91d247de9903c2484d35 (MD5) / Made available in DSpace on 2016-07-28T12:46:53Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) tese_diogotc_final.pdf: 7303783 bytes, checksum: f9959e8bb63b91d247de9903c2484d35 (MD5) Previous issue date: 2016-01-29 / Esta tese apresenta uma metodologia de paralelização híbrida aplicada ao Método dos Elementos Discretos (DEM - Discrete Element Method) que combina MPI e OpenMP com o intuito de melhoria de desempenho computacional. A metodologia utiliza estratégias de decomposição de domínio visando a distribuição do cálculo de modelos de larga escala em um cluster. A técnica proposta também particiona a carga de trabalho de cada subdomínio entre threads. Este procedimento adicional visa obter maiores desempenhos computacionais através do ajuste de utilização de mecanismos de troca de mensagens entre processos e paralelização por threads. O objetivo principal da técnica é reduzir os elevados tempos de comunicação entre processos em ambientes computacionais de memória compartilhada tais como os processadores modernos. A divisão de trabalho por threads emprega a curva de preenchimento de espaço de Hilbert (HSFC) visando a melhoria de localidade dos dados e evitando custos computacionais (overheads) resultantes de ordenações constantes para o vetor de partículas. As simulações numéricas apresentadas permitem avaliar os métodos de decomposição de domínio, técnicas de particionamento, mecanismos de controle de acesso à memória, dentre outros. Algoritmos distintos de particionamento e diferentes estratégias de solução paralela são abordados para ambientes computacionais de memória distribuída, compartilhada ou para um modelo híbrido que envolve os dois ambientes. A metodologia desenvolvida e a ferramenta computacional utilizada nas implementações realizadas, o software DEMOOP, fornecem recursos que podem ser aplicados em diversos problemas de engenharia envolvendo modelos de partículas em larga escala. Nesta tese alguns destes problemas são abordados, em especial aqueles relacionados com fluxo de partículas em rampas, em funis de descarga e em cenários reais de deslizamento de terra. Os resultados mostram que as estratégias de execução híbridas atingem, em geral, melhores desempenhos computacionais que aqueles que se baseiam unicamente em troca de mensagens. A técnica de paralelização híbrida desenvolvida também obtém um bom controle de balanço de carga entre threads. Os estudos de caso apresentados apresentam boa escalabilidade e eficiências paralelas. O método proposto permite uma execução configurável de modelos numéricos do DEM e introduz uma estratégia combinada que melhora localidade dos dados e um balanceamento de carga iterativo. / This thesis introduces a methodology of hybrid parallelization applied to the Discrete Element Method (DEM) that combines MPI and OpenMP to improve computational performance. The methodology uses domain decomposition strategies to distribute the computation of large-scale models in a cluster. It also partitions the workload of each subdomain among threads. This additional procedure aims to reach higher computational performance by adjusting the usage of message passing artifacts and threads. The main objective is to reduce the expensive communications between processes in computer resources of shared memory such as modern processors. The work division by threads employs Hilbert Space Filling Curves (HSFC) in order to improve data-locality and to avoid the overhead caused by the dynamical sorting of the particles array. Presented numerical simulations allow to evaluate several domain decomposition schemes, partitioning methods, mechanisms of memory access control, among others. The work investigate distinct schemes of parallel solution for both distributed and shared memory environments. The method and the computational tool employed, the software DEMOOP, provide applied resources for several engineering problems involving large scale particle models. Some of these problems are presented on this thesis, such as the particle flows that happen on inclined ramps, discharge hoppers and real scenarios of landslides. The results shows that the hybrid executions reach better computational performance than those based on message passing only, including a good control of load balancing among threads. Case studies present good scalability and parallel efficiencies. The proposed approach allows a configurable execution of numerical models and introduces a combined scheme that improves data-locality and an iterative workload balancing.

Light Detection and Ranging (LIDAR) är en teknik för att samla in data om terräng. Genom att använda dessa data kan man skapa olika terrängmodeller. Denna studie syftar till att undersöka hur olika procentuella reduceringar av ursprungsdata påverkar kvalitén hos genererade höjdmodeller i form av Triangular Irregular Network (TIN). Detta görs genom att med hjälp av statistiska metoder göra jämförelser mellan punkter i den genererade TIN modellen och motsvarande punkter i det ursprungliga LIDAR punktmolnet. Studien visar att, beroende på noggrannhetskrav och topografi, en så liten andel som 5 % av punkterna kan vara tillräckligt, samt att noggrannhetsförbättring vid användning av mer än 50 % av ursprungsdata inte kan motivera den ökade arbetsbelastningen för datahantering.

Une approache combinant la méthode des élements discrets (DEM) et expériences techniques (essai oedométrique et microtomographie aux rayons X (XRCT)) est proposée pour observer le comportement mécanique des matériaux granulaires mouillés (des billes de verre mouillées) en état très lâche sous le chargement extérieur. Une observation expérimentale combinant l'essai oedométrique et XRCT est premièrement présentée. La réponse plastique du materiau réel (des billes de verre) est illustrée avec des certaines valeurs de densité initiale très faible. Le comportement à l'échelle du grain de ce matériau est puis caractérisé en utilisant à l'aide de microtomographie aux rayons X et d'essais mécaniques in-situ. Une méthode pour détecter des structures sphériques qui ont obtenu depuis des images de la tomographie est proposée. Ensuite, les propriétés micro-structurales sont analysées et calculées avec les données des sphères détectés. Ce matériau simplifié donne une meilleure compréhension du comportement à macro-échelle des sols granulaires mouillés basée sur leur caractérisation micro-structurale. La simulation numérique a permis de prévoir précisément en 3D la réponse plastique d'assemblages très lâches de billes de verre modélisé soumis à une compression isotrope/ oedométrique. Ce maériau a été préparé avec la présence d'une petite quantité d'un liquide interstitiel qui contrôle à capillaire ménisque and des forces attractives. Les réponses plastiques le long des courbes de compression sont présentées dans les cas avec et sans des résistance au roulement/ pivotement en contacts. L'effet du grain polydispersité en taille a aussi mentionné. L'évaluation de la microstructure et transmission de force le long de la courve de compression est également caractérisé. Finalement, nous comparons les prévisions des résultats expérimentals avec ceux de la simulation numérique. Nos comparaisons montrent que les prévisions de l'expérience sont sous-estimées pour celles de la DEM. Néanmoins, cette approache dans ce travail également fournit une caractérisation complète de la réponse plastique et du comportement à l'échelle du grain de sol granulaire mouillé à l'état très lâche / An approach combining the Discrete Element Method (DEM) and experimental techniques (oedometric compression test and X-ray Computed Tomography (XRCT)) is proposed to observe the mechanical behavior of wet granular material, modeled as frictional spherical glass beads, in very loose state under growing of applied external force. An experimental observation combining one-dimensional compression test and XRCT is first presented. The plastic responses of real material (spherical glass beads) are depicted with different values of very low initial densities. The grain-scale behavior of this material is then characterized by using the XRCT and in-situ compaction test. We propose a method to detect the spherical structures from the 3D tomography images. Microstructure properties of the loose system are then analyzed and computed from the detected spherical structures. This simplified material gives further a better understanding of the macroscale behavior of wet granular soils based on their microstructure characterization. The DEM simulation then allowed us to predict accurately in 3D the plastic response of very loose assemblies of modeled wet beads to an isotropic/ oedometric compression in the presence of a small amount of an interstitial liquid, which gives rise to capillary menisci and attractive forces. The plastic responses along the compression curves are then shown in particular without and with the appearance of rolling/ pivoting resistances in contacts and also the effect of size polydispersity. The evaluation of microstructure and force transmission along the compression curve is also characterized. Finally, we compare the predictions of the experimental results with the DEM simulations results. Our comparisons show that the predictions of experiments are underestimated for the DEM simulations. Nevertheless, the combined approach in this work also provides an comprehensive characterization of the plastic and grain-scale compression behavior of wet granular soil at very loose state

Abstract In the design and development of unit operations in chemical engineering, experimental testing is often very expensive or even impossible to perform. In these kinds of situations, numerical simulations offer a good approach to study process characteristics. Typically in chemical engineering, data-based modeling is applied to study the process. This requires many experiments for tuning the model parameters and validating the model. In a phenomenology-based approach, the evolution of the system is dictated by fluid and particle transport equations. These equations are independent of the process, and can therefore be applied in various systems. However, depending on the system, there are several aspects that have to be taken into account in order to choose the correct model for the problem in hand. In this work, computational fluid dynamics (CFD) and discrete element method (DEM) modeling have been applied in different unit operations in the field of chemical engineering. CFD was applied in preventing sedimentation in a tube heat exchanger, estimating the cooling efficiency of a vertical water jet onto a hot metal plate, and studying the formation of the slag free open-eye area on the steel ladle. For comparison, DEM was applied in the continuous high-shear granulation of pharmaceutical powder. The different models used in this work are reviewed, and the results are presented from the point of view of model and process development. The grid aspects in CFD simulations and the termination criteria for DEM and CFD simulations are also studied. Based on the results of this work, phenomenological modeling can be considered to be an efficient tool for unit operation design. Together with experimental work, different modeling strategies offer a powerful tool for the design and development of unit operations. / Tiivistelmä Kemiantekniikan yksikköprosessien suunnittelussa kokeellinen tutkimus on usein erittäin kallista ja joskus jopa mahdotonta toteuttaa. Tällöin mallinnus tarjoaa hyvän lähestymistavan yksikköprosessin ominaisuuksien tutkimiselle. Tyypillisesti kemianteollisuudessa, datapohjaista mallinnusmenetelmiä on käytetty systeemin ominaisuuksien tutkimiseksi. Tämä menetelmä vaatii kuitenkin paljon koetoistoja mallin parametrien virittämiseksi ja mallin validoimiseksi. Ilmiöpohjaisessa mallinnuksessa, systeemin aikakehitys määräytyy fluidi- ja partikkelivirtauksia määräävien kuljetusyhtälöiden perusteella. Nämä yhtälöt ovat prosessista riippumattomia, jolloin niitä voidaan soveltaa yleisesti mihin tahansa systeemiin. Riippuen kuitenkin tutkittavasta yksikköprosessista, eri asioita on otettava huomioon, jotta oikea malli voidaan valita kuvaamaan systeemiä. Tässä työssä virtauslaskentaa (computational fluid dynamics, CFD) ja partikkelimenetelmää (discrete element method, DEM) on käytetty erilaisten kemiantekniikan yksikköprosessien tutkimuksessa. CFD:n avulla on tutkittu putkilämmönvaihtimen sedimentaation ehkäisyä, laminaarisen suorasuihkujäähdytyksen tehokkuutta teräslevyn jäähdytyksessä, sekä senkkaprosessissa teräksen pinnalle ilmestyvän kuonasilmäkkeen muodostumista. DEM mallinnusta käytettiin lääkejauheen jatkuvatoimisen rakeistuksen tutkimuksessa. Mallinnuksessa käytetyt mallit esitellään ja niiden tulokset esitellään malli- ja prosessikehityksen näkökulmasta. Työssä on otettu myös esille mallinnustekniset asiat CFD:n vaatiman laskentahilan ja laskennan lopetuskriteerien näkökulmasta. Työssä esitettyjen tulosten perusteella voidaan todeta, että ilmiöpohjainen mallinnus on tehokas työkalu yksikköprosessien suunnittelussa. Yhdessä kokeellisen tutkimuksen kanssa, eri mallinnusmenetelmät tehostavat yksikköprosessien suunnittelua ja kehitystä.

The aim of this study is to examine if pupils in the grades 4 - 6 in one school follow Swedish written language norms. The focus on this study is on the Swedish pronouns de, dem and dom. The English equivalent of de and dem is they and them. In the Swedish language we also have the pronoun dom, that is mostly used in colloquial language. This is interesting because its known that pupils today struggle with differentiating de, dem and dom in the Swedish written language. For example, many pupils use colloquial language dom in written language. There is also an ongoing debate about this topic, which I will go more into later in this study. The reason this research is relevant, is because the last time pupils in middle school years 4 - 6 was examined was in the in the 70’s and as I said there is an ongoing debate about the Swedish pronouns de/dem/dom. One of the things that the debate is about, is whether de and dem should be replaced with the colloquial language form dom. The two questions I used to come to a conclusion are: • What pronoun functions do the pupils have difficulties with? (object, subject etc.) • Does the position of the pronoun in the sentence have an impact on what form the pupils use? (does dem/dem här and dom/dom här occur before or after the verb). To answer these questions, I use two cloze procedures. One from Hallencreutz (1980) and the second one is from Håkansson & Norrby (2003). A total of 66 pupils did the cloze procedures. It was 22 pupils from grades 4, 5 and 6 that engaged in this study. The results show that (46 %) of the pupils used the colloquial language dom in the test. When it comes to pronoun functions, a majority of the pupils (59%) failed on the object function. The results also show that the pupils in my study mixed wrong use of dem/dem här and dom/dom här. Sometimes it was used before the verb, and sometimes after the verb. There was no clear pattern that dem/dem här and dom/dom här came after or before the verb, although it is said that dem/dem här and dom/dom här should appear more often after the verb.

Un mur de soutènement en pierre sèche (MSPS) est un ouvrage vernaculaire construit par empilement de blocs rocheux sans liant. Ce type de mur a fortement sculpté les campagnes françaises mais a aussi été utilisé par le passé dans des ouvrages de soutènement que ce soit routier ou ferroviaire. Pourtant, l’utilisation de cette technologie a disparu au cours du 20e siècle au profit de solutions industrialisées comme le béton armé. Face à ce patrimoine vieillissant, il est très difficile de proposer des protocoles de réparation alors que la réglementation associée à ces ouvrages est inexistante. Pour les mêmes raisons, alors que cette technologie répond parfaitement aux questions soulevées par le développement durable, elle est rarement envisagée ou retenue par les prescripteurs. La rupture des MSPSs neufs peut apparaître à cause de : (1) une poussée excessive du remblai soutenu par le mur, (2) un effort concentré excessif présent sur la surface du remblai et proche de la tête du mur. Ces deux causes induisent deux types de rupture très différents, respectivement : (1) rupture en déformation plane, (2) rupture par apparition d’un ventre. Trois expériences récentes à l’échelle 1 des MSPSs chargés par : (1) une poussée hydrostatique, (2) un remblai, (3) un remblai avec une force concentrée sur la surface de ce dernier, ont permis d’identifier certains phénomènes mis en jeu dans ces ruptures. Ce travail de thèse contribuera alors au développement de nouveaux outils scientifiques mais aussi à valider des outils existants pour dimensionner les MSPSs. Les expériences réalisées à l’échelle 1 serviront alors de cadre à ce travail pour valider les outils développés. Nous avons choisi d’utiliser une approche aux éléments discrets (MED) où chaque bloc de pierre du mur est modélisé individuellement, respectant ainsi la nature-Même de l’ouvrage réel. Dans un premier temps, une rupture de type déformation plane est modélisée par une approche discrète pure et une approche discrète-Continue. Les atouts et inconvénients de chacune des méthodes sont mis en avant. Une validation quantitative des modèles numériques est faite en comparant la hauteur critique de chargement avec les expériences à l’échelle 1. Ensuite, on étudie la sensibilité de plusieurs paramètres géométriques et mécaniques sur la hauteur critique de chargement, tout comme l’influence de la cohésion du remblai. Enfin, une première modélisation 3D de type qualitative sur la rupture des MSPS par un chargement concentré en surface du remblai est présentée. Les problèmes de modélisation sont soulevés et l’influence de la forme des blocs dans le processus de rupture est étudiée. / A dry-Stone retaining wall (DSRW) is a vernacular structure constructed by stacking the stone blocks without using any binder. In the past, this wall has been extensively used, shaping the French countryside area, built either for road or railroad retaining wall. However, the use of this technology has disappeared during 20th century, due to the emergence of more industrialized materials such as reinforced concrete. Confronted by these ageing heritage structures, it is very difficult to propose a proper reparation procedure since the building codes associated with this structure are nonexistent. For the same reason, though this technology perfectly answers the questions raised by the concept of sustainable development, in practice this structure is rarely considered or used by the engineering advisors. The failure of the newly built DSRWs can be attributed to the following reasons: (1) an excessive pressure of backfill retained by the wall, (2) a presence of an excessive concentrated load on the backfill surface, close to the top part of the wall. These two types of loading lead to two very different types of failure, respectively: (1) plane strain failure, (2) bulging failure. Three recent experimental campaigns of DSRWs loaded with: (1) hydrostatic pressure, (2) backfill, (3) backfill with a concentrated on its surface, provided a better understanding of phenomena involved in these failures. The work presented in this PhD thesis contributes to the development of new scientific tools capable to help design the DSRWs, as well as validating existing tools. The recent full-Scale experimental campaign will serve as a basis to the validation of the developed numerical tools. We have chosen to use a discrete element method (DEM) where each stone block of the wall is modeled individually, complying with the nature of real DSRW. In the first place, the plane strain failure is modeled by a purely discrete approach and a discrete-Continuum approach. The advantage and inconvenient of each method will be presented in advance. A quantitative validation of numerical models is provided by comparing the critical height of loading with results derived from the full-Scale experimental campaign. Thereafter, a 3D qualitative model of DSRWs loaded with a concentrated load on the backfill surface is presented. The modeling problem is noted and the influence of the block form in regards of the related failure mechanism is studied.