<p>The threats imposed by the ongoing climate change become successively more clear. In the municipality of Sandviken the possible rise in water level in the lake Storsjön might cause major problems. This study aims to produce an elevation model over one of the threatened areas so that the effect of different water levels in the lake can be studied in the future.</p><p>The area of study consists of an esker cutting straight through the lake Storsjön. The area is densely populated and the size is about 13 hectares.</p><p>Measurements were performed, both with GPS, utilizing Network-RTK, and with total station. The formations of the ridge were captured by following the breaklines with a point density of 225 points/ha as an intended goal.</p><p>The GPS measurements were transformed into the local coordinate system of Sandviken municipality. The measured coordinates for six control points were compared to the true coordinates. The fit was not perfect, so a Helmert transformation was performed on the plane coordinates. The accuracy of the measurements was below 50 mm after the transformation. Net adjustments in plane and height were performed on the total station measurements. The error ellipses for the station points varied from 2 to 44 mm. The over all point density achieved was 274 points/ha.</p><p>Two elevation models were created, one Triangular Irregular Network (TIN) and one interpolated model using a kriging interpolation. Contour lines from both models were produced and compared with each other. The TIN creates a more angular surface and therefore the contour lines are not as smooth as in the interpolated model. Both models showed good resemblance compared with the original data.</p> / <p>Problem relaterade till klimatförändringar blir alltmer uttalade. I Sandvikens kommun kan problem uppstå om vattennivåerna i Storsjön stiger. Syftet med det här examensarbetet var att skapa en höjdmodell över ett av de utsatta områdena för att effekter av en eventuell vattennivåhöjning skall kunna studeras i framtiden.</p><p>Området består av en rullstensås som sträcker sig rakt igenom Storsjön. Området är tättbefolkat och ca 13 hektar stort.</p><p>Mätningarna utfördes med både GPS och totalstation. Vid GPS-mätningarna utnyttjades Nätverks-RTK. Åsens formationer fångades genom att följa brytlinjer med en estimerad punkttäthet på 225 punkter/ha.</p><p>GPS-mätningarna transformerades till Sandvikens lokala koordinatsystem. De mätta koordinaterna för sex kontrollpunkter jämfördes med de sanna koordinaterna. Eftersom de mätta värdena inte passade in perfekt så utfördes en Helmerttransformation av plankoordinaterna. Noggrannheten på mätta värden var inom 50 mm efter transformationen. Nätutjämningar i plan och höjd gjordes på totalstationsmätningarna. Felellipserna för stationspunkterna varierade mellan 2 och 44 mm. Den sammanlagda punkttätheten uppgick till 274 punkter/ha.</p><p>Två höjdmodeller framställdes, en TIN-model (Triangular Irregular Network) och en interpolerad model där interpolationsmetoden kriging användes. Höjdkurvor framställda från respektive modell skapades och jämfördes med varandra. Ett TIN ger en mer kantig yta vilket återspeglas i höjdkurvorna som inte är lika jämna som de från den interpolerade modellen. Båda modellerna visade god överensstämmelse med originaldata.</p>

The threats imposed by the ongoing climate change become successively more clear. In the municipality of Sandviken the possible rise in water level in the lake Storsjön might cause major problems. This study aims to produce an elevation model over one of the threatened areas so that the effect of different water levels in the lake can be studied in the future. The area of study consists of an esker cutting straight through the lake Storsjön. The area is densely populated and the size is about 13 hectares. Measurements were performed, both with GPS, utilizing Network-RTK, and with total station. The formations of the ridge were captured by following the breaklines with a point density of 225 points/ha as an intended goal. The GPS measurements were transformed into the local coordinate system of Sandviken municipality. The measured coordinates for six control points were compared to the true coordinates. The fit was not perfect, so a Helmert transformation was performed on the plane coordinates. The accuracy of the measurements was below 50 mm after the transformation. Net adjustments in plane and height were performed on the total station measurements. The error ellipses for the station points varied from 2 to 44 mm. The over all point density achieved was 274 points/ha. Two elevation models were created, one Triangular Irregular Network (TIN) and one interpolated model using a kriging interpolation. Contour lines from both models were produced and compared with each other. The TIN creates a more angular surface and therefore the contour lines are not as smooth as in the interpolated model. Both models showed good resemblance compared with the original data. / Problem relaterade till klimatförändringar blir alltmer uttalade. I Sandvikens kommun kan problem uppstå om vattennivåerna i Storsjön stiger. Syftet med det här examensarbetet var att skapa en höjdmodell över ett av de utsatta områdena för att effekter av en eventuell vattennivåhöjning skall kunna studeras i framtiden. Området består av en rullstensås som sträcker sig rakt igenom Storsjön. Området är tättbefolkat och ca 13 hektar stort. Mätningarna utfördes med både GPS och totalstation. Vid GPS-mätningarna utnyttjades Nätverks-RTK. Åsens formationer fångades genom att följa brytlinjer med en estimerad punkttäthet på 225 punkter/ha. GPS-mätningarna transformerades till Sandvikens lokala koordinatsystem. De mätta koordinaterna för sex kontrollpunkter jämfördes med de sanna koordinaterna. Eftersom de mätta värdena inte passade in perfekt så utfördes en Helmerttransformation av plankoordinaterna. Noggrannheten på mätta värden var inom 50 mm efter transformationen. Nätutjämningar i plan och höjd gjordes på totalstationsmätningarna. Felellipserna för stationspunkterna varierade mellan 2 och 44 mm. Den sammanlagda punkttätheten uppgick till 274 punkter/ha. Två höjdmodeller framställdes, en TIN-model (Triangular Irregular Network) och en interpolerad model där interpolationsmetoden kriging användes. Höjdkurvor framställda från respektive modell skapades och jämfördes med varandra. Ett TIN ger en mer kantig yta vilket återspeglas i höjdkurvorna som inte är lika jämna som de från den interpolerade modellen. Båda modellerna visade god överensstämmelse med originaldata.

Inaug. _ Diss.: Philosophische Fakultät: Köln: 1976. _ Contient le texte de la "Margaretenlegende" de Hartwig von dem Hage. _ Bibliogr. p. 239-252. Index.

Les racines des plantes jouent un rôle important dans la croissance et le développement des plantes, et il est bien connu que les interactions mécaniques entre une croissance racinaire et le sol environnant peuvent avoir un impact majeur sur la croissance des racines et par conséquent sur la production de biomasse végétale. Ces interactions mécaniques sont l'un des nombreux facteurs qui peuvent expliquent la variabilité de l'architecture des racines, y compris les facteurs génétiques, environnementaux et l'instabilité du développement. Mais ce facteur a souvent été sous-estimé. Nous supposons que la structure hétérogène du sol à l'échelle des grains, démontrée par la large répartition des forces, peut influencer d'une manière significative sur les trajectoires de croissance des racines. Ce travail de thèse vise à déterminer comment les grains dans les sols granulaires se réorganisent sous l'action de la croissance des racines, et en retour, comment les forces résultantes agissant sur les apex des racines modifient leur développement, y compris la cinématique de leurs trajectoires. Nous avons développé un modèle numérique 2D de la croissance des racines dans un milieu granulaire en utilisant la méthode des éléments discrets (DEM). Le modèle est capable de calculer les forces de contacts grain-grain et racine-grain dans un milieu granulaire. Le système racinaire est modélisé en utilisant des chaînes d'éléments de spheroline connectés. L'orientation de la croissance des racines, à chaque étape de croissance est déterminée par la dynamique de la racine entière sous l'action des forces élastiques internes et des forces de réaction exercées par les grains, ces sont les interactions mécaniques qui contrôlent la croissance numérique dans le modèle.Des études paramétriques ont été réalisées afin (i) d'estimer l'influence de la structure granulaire (distribution de grains de diamètre, la cohésion, la fraction volumique ...) et les propriétés mécaniques des racines (la rigidité à la flexion) sur le signal de force axiale agissant sur la pointe de la racine, et sur les trajectoires et (ii) de définir les lois physiques générales qui peuvent être utilisées en outre pour analyser des données expérimentales. Les courbes de distribution des forces axiales calculées normalisées par leurs moyens au cours d'une période donnée de la croissance, sont caractérisées par une loi de puissance décroissante pour les forces en dessous de la force moyenne, et une décroissance exponentielle pour les forces ci-dessus de la force moyenne, reflétant ainsi la large répartition des forces à l'intérieur d'un matériau granulaire. Une analyse de l'écart-type des déformations locales des trajectoires des racines, résulte deux régimes en fonction la rigidité de la racine. Une première lorsque le sol contrôle les déformations des racines, et une deuxième lorsque la racine est trop rigide, et se déplace plus les grains environnants durant la croissance. / Plant roots play an important role in the growth and development of plants, and it is well known that the mechanical interactions between a growing root and the surrounding soil can have a major impact on root growth and consequently on plant biomass production. These mechanical interactions are one of numerous factors that explain the variability of root architecture, including genetics, environment and developmental instability. But this factor has often been under-estimated. I hypothesize that the heterogeneous structure of soil at the particle scale, demonstrated by the broad distribution of forces, can significantly influence root growth trajectories. This thesis aims at determining how grains in granular soils are reorganized under the action of growing roots, and in return how the resulting forces acting on root tips modify their development, including the kinematics of their trajectories, in order to develop a general biophysical law of root-soil mechanical interactions. I developed a 2D numerical model of root growth in a granular medium using a Discrete Element Model (DEM). The model is able to compute grain-grain and root-grain contact forces within a granular medium. The root system is modelled using chains of connected spheroline elements. The orientation of root growth at every growth step is determined by the dynamics of the whole root under the action of its internal elastic forces and reaction forces exerted by the grains, which are the mechanical interactions that control numerical growth in the model.Parametric studies were carried out in order to (i) estimate the influence of granular structure (grain diameter distribution, cohesion, volume fraction) and root mechanical properties (root bending stiffness) on the axial force signal acting on the root tip, and on the root trajectories and (ii) define general physical laws that can be used further to analyze experimental data. The distribution curves of computed root tip-grain forces normalized by the mean force during a given period of growth were characterized by a decreasing power law for forces below the mean force, and an exponential fall-off for forces above the mean force, thus reflecting the broad distribution of forces inside the granular material. An analysis of the standard deviation of the local deformations of root trajectories resulted in two different regimes with regard root stiffness. In the first regime, soil controlled the root deformation and in the second, the root trajectory was straighter and displaced more significantly the surrounding grains during growth.

Les composants optiques de silice traversés par des flux lasers de haut niveau d'énergie à des longueurs d'onde de 351 nm peuvent être soumis à des endommagements. Il est admis que la présence de microfissures en sous surface, induit par les procédés d'abrasion des composants optiques, joue un rôle clé dans l'initiation des dommages lasers. Cette thèse propose de simuler le procédé de surfaçage par la méthode des éléments discrets afin de caractériser la densité et la répartition des microfissures en fonction des paramètres d'usinage. / When fused silica optics are submitted to high-power laser (such as megajoule laser or National Ignition Facility) at the wavelength of 351 nm, fused silica optics can exhibit damage, induced by the high amount of energy traversing the part. Current researches have shown that this damage could be initiated on pre-existing sub-surface damages created during the polishing processes. The discrete element method (DEM) is proposed to simulate the polishing process and its impact on sub-surface damage creation.

Fluidization of solid particles using gas flow is an important process in chemical and pharmaceutical industries. The dynamics of fluidisation are intricately related to particle scale physics. Fluid-particle interactions dominate gas-solid fluidization behaviour for particles with average size and density greater than 10-4 m and 103 kg/m3, respectively, classified as Geldart B and D particles. Inter-particle forces, such as cohesion, play an increasingly important role in the fluidization dynamics of smaller particles, which are classified as Geldart A and C. In particular, interesting fluidization regimes have been noticed for weakly cohesive Geldart A particles, exhibiting a window of uniform fluidization before the onset of bubbling behaviour. Despite widespread industrial interests, the fundamental understanding of the mechanisms that underlie these fluidization regimes is poor. The present study aims to improve the understanding of fluidization dynamics of Geldart A regimes using numerical simulations. A DEM-CFD model was employed to capture the widely separated spatial and temporal scales associated with fluidization behaviour. The model couples the locally averaged Navier-Stokes equation for fluid with a discrete description of the particles. The methodology and its computer implementation are verified and validated to assess the extent of fluidization physics that it is able to capture. Verification cases check the implementation of the inter-phase momentum transfer term, drag model implementation and pressure-velocity coupling. The test cases are employed in order to cover a wide range of flow conditions. Robust validation tests for complex fluidization phenomena such as bubbling, spouting and bidisperse beds have been conducted to assess the predictive capabilities of the DEM-CFD solver. The simulation results for time and spatially averaged fluidziation behaviour are compared to experimental measurements obtained from the literature, and are shown to have capture fluidization physics qualitatively. Robust features of bubbling fluidization, such as minimum fluidization velocity, frequency of pressure drop fluctuations, segregation rates and solid circulation patterns were captured. Furthermore, the DEM-CFD model is critically assessed in terms of model conceptualization and parameter estimation, including those for drag closures, particle-wall boundary conditions, bed height and particle shape effects. The validation studies establish modelling best-practice guidelines and the level of discrepancy against the analytical solutions or experimental measurements. Having developed the model and established its predictive capability, it is used to probe the hydrodynamics of weakly cohesive particles. Cohesive interactions are captured by employing a pair-wise van derWaals force model. The cohesive strength of the granular bed is quantified by the ratio of the maximum van der Waals force to the particle gravitational force, defined as the granular Bond number. The Bond number of the bed is increased systematically from 0-10 to examine the role of cohesion in the fluidization behaviour of fine powders while keeping the particle size and density constant across all the simulations. The idea was to segregate the hydrodynamics associated with size and density of the particles from the inter-particle interactions. The size and density of the particles are carefully chosen at a scale where inter-particle forces are present but minimal [Seville et al., 2000]. The Geldart A fluidization behaviour is captured for granular beds with Bond numbers ranging from 1 to 3. Many robust features of Geldart A fluidization, such as pressure drop overshoot, delay in the onset of bubbling, macroscopic Umf predictions and uniform bed expansion are captured in the DEM-CFD framework. The expanded bed was characterized according to criteria that the particles are highly immobile in this regime and the expanded porosity is related to inlet velocity by Richardson–Zaki correlations. Sudden jumps in the magnitudes of global granular temperature were found near the regime transitions. This observation was used an indicator of the onset of bubbling and quantification of minimum bubbling velocity (Umb). The window of the expanded bed regime (quantified as Umb - Umf) was shown to be an increasing function of cohesive strength of the bed. Furthermore, the stability of the expanded bed was probed by studying the response of the expanded bed to sudden inertial and voidage shocks. A kinematic wave, generated as a response to the voidage shock, was shown to slow down with increasing cohesion and decreasing hydrodynamic forces. Furthermore, predictions of Umb by DEM-CFD simulations for weakly cohesive beds were compared against empirical correlations by Valverde [2013] with an excellent match. Stress analysis of the expanded bed revealed the presence of tensile stresses. As the inlet velocity is increased beyond the minimum fluidization velocity, a longitudinal shift of these negative stresses is observed until they reach the top of the bed. Negative stresses were seen at the bed surface at the onset of bubbling. The role of cohesion stresses in the formation of expanded bed and suppression of bubbling was highlighted. Finally, the microstructure of the expanded bed was probed at different local micro and mescoscopic length scales. Evidence of clustering, agglomeration and cavities were presented in the expanded bed. Expanded bed expansion was shown to have mesostructural inhomogeneities present, which is contrary to the belief of homogeneous expansion.

This research analyzes the sensitivity of watershed attributes, and hydrological outputs to LiDAR derived DEM uncertainty introduced through spatial resolution, and LiDAR measurement errors. Sensitivity of watershed attributes to spatial resolution was determined through a scaling analysis at three sites; Mosquito Creek, Scotty Creek and Thomas Brook, with DEMs ranging from 1 to 50 m. Results at Scotty Creek showed the highest sensitivity of watershed area to spatial resolution, due to subtle changes in elevation which were below DEM uncertainty. Validation of the stream length at Thomas Brook showed discrepancies of 3.7 to 24.1% for the 1 to 50 m DEMs, compared to independent field observations. Sensitivity of SWAT derived hydrological outputs to DEM spatial resolution were determined through a scaling analysis of DEMs (1 - 50 m) at Thomas Brook watershed, over a five year simulation period. Results indicated monthly water yield was insensitive to DEM resolution, unless a change in area was also present. Sediment yield from the 50 m DEM showed a 24% reduction compared to the 1 m DEM. The 5 - 50 m DEMs also showed a reduction in channel deposition of 45 - 90 t, compared to the 1 m DEM. Sensitivity of terrain attributes, watershed attributes and hydrological outputs to LiDAR measurement errors were determined at the Thomas Brook watershed through the propagation of LiDAR sensor measurement errors with Monte Carlo simulations. Results showed that the uncertainty in the DEM, slope, and aspect were below 0.06 cm, 1.5° and 24.1° in 97.5% of grid cells, respectively. Watershed area and stream length resulted in relative standard deviations of <1% and 1.5%, respectively. However, sensitivity of watershed area increased in regions with elevation changes below DEM uncertainty and stream length uncertainty increased with decreasing stream length. SWAT simulated flow and sediment showed minor sensitivity to LiDAR measurement error in high flow months, and increased as flow decreased. Simulated sediment showed higher sensitivity to LiDAR measurement errors than flow, due to changes in the HRU slope class, which can shift the dominant HRU (Hydrological Response Unit) if a minimum HRU threshold area is implemented.

The Soil Water Retention Curve (SWRC) is a key constitutive relationship describing the behavior of variably saturated soils. The objective of this research is to assess the performance of a hydro-mechanical model, developed by coupling the lattice Boltzmann method (LBM) with the discrete element method (DEM), for micromechanical simulation of the SWRC. The DEM-LBM model is used to examine the effects of wave propagation on fluid-solid interaction. A multi-phase LBM is then employed within a static particle array generated by the DEM to examine the effects of initial fluid density distribution. The SWRCs are generated by recording the liquid pore pressure and the degree of saturation within a porous medium subjected to imbibition for two cases: randomized fluid density simulation (non-unified wetting front) and droplet simulation (unified wetting front). The coupled DEM-multiphase LBM model is shown to be a promising tool to characterize capillary regime in partially saturated porous media.

No description available.

Ce travail s’inscrit dans le projet LORVER, soutenu par la Région Grand Est et le FEDER. Il est destiné à créer une filière de production de biomasse végétale non alimentaire par valorisation de sites dégradés et de sous-produits industriels, en Lorraine. Un des procédés de valorisation de la biomasse produite est un procédé thermochimique de pyro-gazéification qui générerait de la chaleur et de l’électricité. Ce procédé, développé par SEA Marconi, se compose de trois réacteurs différents : un tambour tournant, pour la pyrolyse de particules de bois, la chaleur étant amenée par des billes d’acier chauffées ; un réacteur à vis sans fin pour l’oxydation du char qui permet de réchauffer les billes d’acier ; un réacteur de craquage des goudrons. L’objectif de cette thèse est de réaliser des modèles qui puissent permettre d’avoir une prédiction adaptée du comportement du système. Des modèles 3D du type DEM et CFD-DEM ont été conçus pour la modélisation des phénomènes qui interviennent dans le système. Les paramètres du modèle DEM ont été calibrés dans un tambour tournant de laboratoire. Pour le réacteur de pyrolyse, la simulation DEM a permis de prédire de façon satisfaisante la ségrégation pour des mélanges de billes d’acier et de particules non sphériques de bois, et de concevoir un modèle thermique et chimique 1D, sur lequel une étude de sensibilité a été effectuée. Un modèle CFD-DEM a été codé et validé sur un rhéomètre granulaire, permettant la simulation du réacteur d’oxydation partielle du char, qui n’a pas pu être réalisé dans le cadre de cette thèse / This work is part of the LORVER project, funded by Grand Est Région and FEDER. It aims to create a non-food biomass production chain by using and upgrading brownfields and industrial by-products in Lorraine. One possible valorization process of the produced biomass is a thermochemical pyro-gasification process that would generate heat and electricity. This process, developed by SEA Marconi, involves three different reactors: a rotating drum, for the pyrolysis of wood particles, the heat required being brought by hot steel balls; an Auger for partial oxidation of the char that allows heating the steel balls; a reactor for tar cracking. The aim of this thesis is to develop models that can predict the behavior of the system. 3D models based on DEM or CFD - DEM were designed for the modeling of phenomena involved in the system. The DEM model parameters were first calibrated in a rotating drum. The DEM simulation was able to predict in a satisfactory manner segregation between steel balls and non-spherical wood particles; it also helped to design a 1D thermal and chemical model, on which a sensitivity study has been done. A CFD - DEM model has been coded and validated on a granular rheometer allowing the simulation of the char oxidation reactor, even if this simulation was not possible during the PhD