• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 8
  • 5
  • 5
  • 4
  • 2
  • 1
  • 1
  • Tagged with
  • 30
  • 30
  • 7
  • 5
  • 5
  • 5
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 3
  • 3
  • 3
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Etude de l'exportation de carbone organique à l'échelle de la mer Méditerranée à l'aide de la modélisation couplée physique/biogéochimie / Study of organic carbon export in the Mediterranean Sea using a coupled biogeochemistry/physic model

Guyennon, Arnaud 17 December 2015 (has links)
Ce travail s'inscrit dans le cadre du projet SIMED fédérant les activités de modélisation à l'échelle méditerranéenne, et plus globalement dans le programme MERMEX qui vise à étudier les cycles biogéochimiques en mer Méditerranée et leurs évolutions futures. L'étape préliminaire a été de coupler la plateforme de modélisation hydrodynamique (NEMO) à celle de modélisation biogéochimique mécaniste (Eco3M), afin de réaliser une simulation (2000-2012) utilisant les sorties hydrodynamiques de la configuration NEMO-MED12 pour forcer le modèle biogéochimique Eco3M-MED. Les nombreuses comparaisons menées dans cette thèse (chlorophylle, sels nutritifs, production primaire, etc.) ont aidé à s'assurer de la capacité du modèle à reproduire les principales caractéristiques biogéochimiques de la Méditerranée. Ce travail a permis de généraliser le rôle majeur joué par le carbone organique dissous dans la pompe biologique à l'échelle de la mer Méditerranée. Les résultats montrent que la production de carbone organique particulaire est restreinte aux régions de forte dynamique physique, tandis que l'accumulation de carbone organique dissous dans les eaux de surface est commune à la plupart des régions du bassin. Ce dernier processus s'est avéré dépendant des contenus cellulaires du phytoplancton et des bactéries hétérotrophes. Finalement d'après le modèle, la fraction dissoute du carbone organique contribuerait à hauteur d'environ 64 % à l'exportation dans le bassin Ouest, et de 90 % dans le bassin Est. Le bassin Est -en dépit de sa plus forte oligotrophie- s'avère participer à près de 60 % à l'exportation de carbone organique en mer Méditerranée. / This work is part of the SIMED project which is dedicated to basin-scale modeling of the Mediterranean Sea. It also belongs to the MERMEX program which aims at studying biogeochemical cycles in the Mediterranean Sea and their evolution. The first step of this work was to couple the hydrodynamic modeling platform (NEMO) to the mechanistic biogeochemical modeling platform (Eco3M). We ran a simulation (2000-2012) using the hydrodynamic outputs from NEMO-MED12 configuration to force the biogeochamical model Eco3M-MED. The model evaluation was conducted using numerous field measurements (chlorophyll, nutrients, primary production, etc.). The simulation strengthens and extends to the whole basin the prominent role of dissolved organic carbon in the biological carbon pump in the whole Mediterranean Sea. A comprehensive analysis of organic carbon (particulate and dissolved) production processes production was performed. Results reveal that particulate organic carbon production is restricted to the highly dynamic areas, whereas dissolved organic carbon accumulation in the surface layers is a common process in much areas of the basin. This latter process appeared to dependant on the cellular contents of phytoplancton and heterotrophic bacteria, themselved being controled by low phosphate availability. Finally, the dissolved organic carbon contribution to carbon export is around 64 % in the Western basin, and up to 90 % in the Eastern basin. When taking into account the dissolved fraction, total organic carbon export in the Eastern basin -despite its higher oligotrophy- exceeds the one in the Western basin (60% against 40 %).
22

Development of a One-Way Coupled Diffraction/Trapped Air Model for Predicting Wave Loading on Bridge Superstructure Under Water Wave Attack

Matemu, Christian Hillary 01 January 2018 (has links)
In recent years, a number of researchers have applied various computational methods to study wind wave and tsunami forcing on bridge superstructure problems. Usually, these computational analyses rely upon application of computational fluid dynamic (CFD) codes. While CFD models may provide reasonable results, their disadvantage is that they tend to be computationally expensive. During this study, an alternative computational method was explored in which a previously-developed diffraction model was combined with a previously-developed trapped air model under worst-case wave loading conditions (i.e. when the water surface was at the same elevation as the bottom bridge chord elevation). The governing equations were solved using a finite difference algorithm in MATLAB for the case where the bridge was impacted by a single wave in two dimensions. Resultant inertial and drag water forces were computed by integrating water pressure contacting the bridge superstructure in the horizontal and vertical directions, while resultant trapped air forces (high-frequency oscillatory forces or sometimes called “slamming forces” in the literature) were computed by integrating air pressure along the bottom of the bridge deck in the vertical direction. The trapped air model was also used to compute the buoyancy force on the bridge due to trapped air. Results were compared with data from experiments that were conducted at the University of Florida in 2009. Results were in good agreement when a length-scale coefficient associated with the trapped air model was properly calibrated. The computational time associated with the model was only approximately one hour per bridge configuration, which would appear to be a significant improvement when compared with other computational technique
23

Modeling of the Haltere-A Natural Micro-Scale Vibratory Gyroscope

Parween, Rizuwana January 2015 (has links) (PDF)
Vibratory gyroscopes have gained immense popularity in the microsystem technology because of their suitability to planar fabrication techniques. With considerable effort in design and fabrication, MEMS (Micro-electro-mechanical-system) vibratory gyroscopes have started pervading consumer electronics apart from their well known applications in aerospace and defence systems. Vibratory gyroscopes operate on the Coriolis principle for sensing rates of rotation of the r tating body. They typically employ capacitive or piezoresistive sensing for detecting the Coriolis force induced motion which is, in turn, used to determine the impressed rate of rotation. Interestingly, Nature also uses vibratory gyroscopes in its designs. Over several years, it has evolved an incredibly elegant design for vibratory gyroscopes in the form of dipteran halteres. Dipterans are known to receive mechanosensory feedback on their aerial rotations from halteres for their flight navigation. Insect biologists have also studied this sensor and continue to be fascinated by the intricate mechanism employed to sense the rate of rotation. In most Diptera, including the soldier fly, Hermetia illucens, the halteres are simple cantilever like structures with an end mass that probably evolved from the hind wings of the ancestral four-winged insect form. The halteres along with their connecting joint with the fly’s body constitute a mechanism that is used for muscle-actuated oscillations of the halteres along the actuation direction. These oscillations occur in the actuation plane such that any rotation of the insect body, induces Coriolis force on the halteres causing their plane of vibration to shift laterally by a small degree. This induced deflection along the sensing plane (out of the haltere’s actuation plane) results in strain variation at the base of the haltere shaft, which is sensed by the campaniform sensilla. The goal of the current study is to understand the strain sensing mechanism of the haltere, the nature of boundary attachments of the haltere with the fly’s body, the reasons of asymmetrical geometry of the haltere, and the interaction between both wings and the contralateral wing and haltere. In order to understand the haltere’s strain sensing mechanism, we estimate the strain pattern at the haltere base induced due to rotations about the body’s pitch, roll, and yaw axes. We model the haltere as a cantilever structure (cylindrical stalk with a spherical end knob) with experimentally determined material properties from nanoindentation and carry out analytical and numerical (finite element) analysis to estimate strains in the haltere due to Coriolis forces and inertia forces resulting from various body rotations. From the strain pattern, we establish a correlation between the location of maximum strain and the position of the campaniform sensilla and propose strain sensing mechanisms. The haltere is connected to the meta thoracic region of the fly’s body by a complicated hinge mechanism that actuates the haltere into angular oscillations with a large amplitude of 170 ◦ in the actuation plane and very small oscillation in the sensing plane. We aim to understand the reason behind the dissimilar boundary attachments along the two directions. We carry out bending experiments using micro Newton force sensor and estimate the stiffness along the actuation and sensing directions. We observe that the haltere behaves as a rigid body in the actuation direction and a flexible body in the sensing direction. We find the haltere to be a resonating structure with two different kinds of boundary attachments in the actuation and sensing directions. We create a finite element model of the haltere joint based on the optical and scanning microscope images, approximate material properties, and stiffness properties obtained from the bending experiments. We subsequently validate the model with experimental results. The haltere geometry has asymmetry along the length and the cross-section. This specific design of the haltere is in contrast to the the existing MEMS vibratory gyroscope, where the elastic beams supporting the proof mass are typically designed with symmetric cross-sections so that there is a mode matching between the actuation and the sensing vibrations. The mode matching provides high sensitivity and low bandwidth. Hence, we are interested in understanding the mechanical significance of the haltere’s asymmetry. First, we estimate the location of the maximum stress by using the actual geometry of the haltere. Next, by using the stiffness determined from bending experiments and mass properties from the geometric model, we find the natural frequencies along both actuation and sensing directions. We compare these findings with existing MEMS vibratory gyroscopes. The dipteran halteres always vibrate at the wing beat frequency. Each wing maintains 180 ◦ phase difference with its contralateral haltere and the opposite wing. Both wings and the contralateral wing-haltere mechanism exhibit coupled oscillatory motion through passive linkages. These linkages modulate the frequency and maintain the out- of-phase relationship. We explore the dynamics behind the out-of-phase behaviour and the frequency modulation of the wing-wing and wing-haltere coupled oscillatory motion. We observe that the linear coupled oscillatory model can explain the out-of-phase relationship between the two wings. However, a nonlinear coupled oscillator model is required to explain both frequency synchronization and frequency modulation of the wing with the haltere. We also carry out a finite element analysis of the wing-haltere mechanism and show that the out-of-phase motion between the wing and the haltere is due to the passive mechanical linkage of finite strength and high actuation force. The results of this study reveal the mechanics of the haltere as a rate sensing gyroscope and show the basis of the Nature’s design of this elegant sensor. This study brings out two specific features— the large amplitude actuated oscillations and the asymmetric geometry of the haltere structure— that are not found in current vibratory gyroscope designs. We hope that our findings inspire new designs of MEMS gyroscopes that have elegance and simplicity of the haltere along with the desired performance.
24

Étude numérique et asymptotique d'une approche couplée pour la simulation de la propagation de feux de forêt avec l'effet du vent en terrain complexe

Proulx, Louis-Xavier 08 1900 (has links)
No description available.
25

Vázané modelování asynchronního motoru metodou konečných prvků / Coupled modeling of induction motor using finite element method

Gregor, Tomáš January 2015 (has links)
This thesis describes complex modeling of asynchronous motor by finite element method. Complex modeling concerns to making models based on different physical principles and their connection. Models are made in Ansys program components and their connection is made in program Ansys Workbench. This thesis includes creating electromagnetic model, thermal model, mechanical model and coupled model which connect partial models.
26

Pier Streamlining as a Bridge Local Scour Countermeasure and the Underlying Scour Mechanism

Li, Junhong, Li 23 May 2018 (has links)
No description available.
27

Höjddata i översvämningsmodellering : En fallstudie om hur höjdmodellens upplösning kan förbättra precisionen hos den 1D/2D-kopplade hydrauliska modellen LISFLOOD-FP / Elevation data in inundation modelling : A case study about how the resolution of the digital elevation model can increase the precision for the 1D-2D coupled hydraulic model LISFLOOD-FP

Ekholm, Disa January 2022 (has links)
Syftet med fallstudien var att undersöka möjligheterna och nyttan med att implementera en höjdmodell med högre upplösning i SMHI:s översvämningsmodellering som tillämpar den hydrauliska modellen LISFLOOD-FP. SMHI utfärdar översvämningsvarningar och det är därför av vikt att översvämningsmodelleringen håller hög kvalitet. Samtidigt kräver modelleringen tid och resurser från Nationellt Superdatorcentrum i Linköping, NSC. Därför vägdes de potentiella fördelarna med högre upplösning mot förlängd körtid. Fallstudien bestod av två delar där en höjdmodell på två meters upplösning i xy-planet implementerades och jämfördes med den i dagsläget uppställda modellen på fem meters upplösning. Detta gjordes genom att återskapa översvämningstillfällen med dess flöden från S-HYPE och mätningar. I studiens första del hämtades satellitdata från Copernicus från två tidigare översvämningstillfällen för validering av över-svämningsmodelleringen. De tidigare översvämningstillfällena var dels i Emån i Småland år 2012 och dels i Västerdalälven i Dalarna år 2018. Ett index för passning beräknades mellan översvämningskartorna producerade med två respektive fem meters upplösning gentemot satellitbilderna för att kvantifiera överlappande ytor. Därtill beräknades vattendragens lutning för att undersöka om det fanns indikationer på något samband med förändring i index med ökad upplösning på höjdmodellen. Studiens andra del bestod i att undersöka hur höjdmodellens upplösning påverkar vattnets spridning kring översvämningsvallar i modellen. I undersökningen återskapades ett översvämningstillfälle från 2020 i Helige å i Småland. Ett antal delavrinningsområden visade sig instabila för den högre upplösta höjdmodellen och kunde därför endast simuleras med lägre flöden. Erhållna resultat visade dock på att översvämningskarteringen förbättrades med upplösningen två meter vid jämförelse med data från Copernicus. Körtiden ökade dock med över 12 gånger vid simulering av högre upplösning. Vidare visades tröskeleffekter i studiens resultat, då översvämnings-vallen stoppade vattnet i den högre upplösta höjdmodellen men inte i den med lägre upplösning. På grund av stabilitetsproblemet och studiens begränsade omfattning, kunde slutsats inte dras om huruvida SMHI bör implementera en höjdmodell med två meters upplösning i systemet för översvämningsvarningar. Däremot kunde konstateras att stabiliteten i modellen måste öka för att det ska vara möjligt. Slutligen drogs slutsatsen att det förekommer tröskeleffekter mellan de två höjdmodellerna och att prestandan ökar generellt för den högre upplösningen när det kommer till precisionen i översvämningsmodelleringen. / The purpose of this case study was to examine the possibilities and advantages of implementing a DEM with higher resolution in inundation modelling at SMHI, the Swedish Meteorological and Hydrological Institute, which uses the hydraulic model LISFLOOD-FP. The institute issues flood warnings and therefore it is of high importance that the innundation modelling gives adequate results. On the other hand, running the models at a higher spatial resolution takes more time and resources. Therefore, potentially improved modelling results were discussed in a context of prolonged runtime. The case study consisted of two parts where a Digital Elevation Model, DEM of two meter resolution was implemented and compared to the five meter DEM that is currently in use. This was done by recreating previous flooding events by using discharge data from S-HYPE. In the first part, satellite data from Copernicus from two previous flooding events in Sweden were used for model validation in comparison with the results from inundation models of SMHI for the different DEM:s. An index was calculated to quantify the overlapping inundation areas. The events were at the river Emån in 2012 and at Västerdalälven in 2018. Moreover, the slope of the rivers within each study area was calculated to investigate correlation between improved flood modelling results for higher DEM resolution and slope of the rivers. The second part of the study investigated flood embankments for the two different DEM:s around Helige å river. A flooding event which took place in 2020 was recreated and the water flow around the built embankments was compared for the two resolutions.  Running the models, it turned out that simulations of several subcatchment areas were unstable with the two meter DEM, and could only be run with lower flow. The obtained results, however, revealed an improved inundation modelling for the DEM with a resolution of 2 m for all study areas in comparison to the data from Copernicus; however the runtime was increased by over 12 times. Moreover, the results also showed threshold effects, where the flooding was impeded by the flooding embankment with the two meter DEM but not at the lower resolution. Due to the stability issue and the limited scope of this study, it cannot be concluded whether SMHI should implement the two meter DEM in their flood warnings system. However, it was concluded that the stability has to be increased to make it feasible. It was also concluded that there are threshold effects between the two DEM:s and that the performance seems to increase overall for the higher resolution when it comes to precision of the modelling.
28

Réponse des masses d'eau intermédiaires et modales de l'océan Austral au mode annulaire austral : les processus en jeu et rôle de la glace de mer / Antarctic Intermediate and Subantarctic Mode waters response to the Southern Annular Mode : processes involved and the sea-ice role

Mainsant, Gildas 28 November 2014 (has links)
Les tendances climatiques récentes montrent un réchauffement et un adoucissement des couches de surface dans la région du courant circumpolaire antarctique (ACC).Sur la même période, les vents d'ouest pilotant la circulation de l'océan Austral ont significativement augmentés. Cette augmentation est en partie liée à l'intensification du mode annulaire austral (SAM), principal mode de variabilité atmosphérique au sud de 20°S. Dans cette thèse, on s'intéresse à comprendre les effets de la tendance positive du SAM sur les propriétés des masses d'eau formées dans la région de l'ACC.A cette fin, on met en place une stratégie de simulations régionales couplées océan-glace de mer et forcées par une série de scénarios atmosphériques perturbés. Les scénarios atmosphériques sont construits à partir de réanalyses atmosphériques afin de décrire les différentes composantes (dynamiques et thermodynamiques) des changements liés au SAM.En réponse à l'intensification du SAM, les simulations montrent une forte salinisation de la couche de mélange océanique ainsi que des eaux modales (SAMW) et intermédiaires (AAIW).L'essentiel de ces changements peut être attribué aux composantes dynamiques du SAM. Dans les régions saisonnières englacées, les composantes thermodynamiques du SAM peuvent jouer un rôle important (en particulier en mer d'Amundsen et en mer de Weddell). Les simulations montrent également le rôle clef joué par la glacede mer dans la médiation des changements atmosphériques vers l'océan intérieur. Ces résultats de simulations suggèrent que le SAM ne serait pas le seul pilote des tendances climatiques récentes dans l'océan Austral. / Recent climate trends show a warming and freshening of the surface layers in the region of the Antarctic Circumpolar Current (ACC). Over the same period, the westerlies driving the circulation of the Southern Ocean have significantly increased. This increase is partly due to the intensification of the Southern Annular Mode (SAM), the main mode of atmospheric variability south of 20°S. In this thesis, we are interested in understanding the effects of the positive trend of the SAM onto the properties of water masses formed in the region of the ACC. To do so, we implement a strategy of regional coupled ocean-sea ice simulations forced by a series of atmospheric disturbance scenarios.These scenarios are constructed from atmospheric reanalyses in order to describe the various components (dynamic and thermodynamic) of the changes related to the SAM. In response to the increase of the SAM, the simulations show a significant salinification of the ocean mixed layer and of the mode water (SAMW) and intermediate water (AAIW).Most of these changes can be attributed to the dynamic components of the SAM. In Seasonal Ice Zone, the thermodynamic components of the SAM can play an important part (especially in Amundsen Sea and Weddell Sea). The simulations also show the key role played by sea ice in mediating atmospheric changes toward the interior ocean.These simulation results suggest that SAM is not the only driver of recent climate trends in the Southern Ocean.
29

A Hydroclimatological Change Detection and Attribution Study over India using CMIP5 Models

Pattanayak, Sonali January 2015 (has links) (PDF)
As a result of increase in global average surface temperature, abnormalities in different hydroclimatic components such as evapotranspiration, stream flow and precipitation have been experienced. So investigation has to be carried out to assess the hidden abnormality subsisting in the hydroclimatological time series in the form of trend. This thesis broadly consists of following four parts. The first part comprises of a detailed review of various trend detection approaches. Approaches incorporating the effect of serial correlation for trend detection and interesting developments concerning various non parametric approaches are focused explicitly. Recent trends in annual, monthly, and seasonl (winter, pre-monsoon, monsoon and post-monsoon) Tmax and Tmin have been analyzed considering three time slots viz. 1901-2003, 1948-2003 and 1970-2003. For this purpose, time series of Tmax and Tmin of India as a whole and for seven homogeneous regions, viz. Western Himalaya (WH), Northwest (NW), Northeast (NE), North Central (NC), East coast (EC), West coast (WC) and Interior Peninsula (IP) were originally considered. During the last three decades significant upward trend in Tmin is found to be present in all regions considered either at annual or seasonal level. Sequential Mann Kendall test revealed that most of the significant upward trends both in Tmax and Tmin began after 1970. The second part discusses about numerous climate models from both Coupled Model Inter comparison Project-5 and 3 (i.e. CMIP5, CMIP3) and their skills in simulating Indian climate and assessing their performance using various evaluation measures. Performances of climate models were evaluated for whole of India and over all the individual grid points covering India. The newly defined metric symbolized as Skill_All is an intersection of the three metrics i.e. Skill_r, Skill_s and Skill_rmse, is used for overall model evaluation analysis. A notable enhancement of Skill_All for CMIP5 over CMIP3 was found. After overall model evaluation study, Compromise Programming, a distance based decision making technique, was employed to rank the GCMs gridwise. Entropy method was employed to obtain weights of the chosen indicators. Group decision making methodology was used to arrive at a consensus based on the ranking pattern obtained by individual grid points. In the third part, a detailed detection and attribution (D&A) analysis is performed to determine the causes of changes in seasonal Tmax and Tmin during the period 1950-2005. This formal D&A exercise helps in providing better insight (than trend detection analysis) into the nature of the observed seasonal temperature changes. It was noticed that the emergence of observed trend was more pronounced in Tmin compared to Tmax. Although observed changes were not solely associated with one specific causative factor, most of the changes in Tmin are above the bounds of natural internal climate variability. Finally in the fourth part, to understand the climate change impact on the hydrological cycle, a spatiotemporal change detection study of potential evapotranspiration (PET) along with Tmax and Tmin over India has been performed. Climatology patterns for PET confirmed a greater PET rate during the month of March, April, May and June. A significant increasing trend in both Tmax and Tmin (Tmin being more) was observed in more number of grid points compared to PET. Significant positive trends in Tmax, Tmin and PET were observed over most of the grid points in the IP region. Heterogeneities existed in the spatiotemporal variability of PET over all India. This spatio-temporal change detection study would be helpful for present and future water resources management.
30

Modélisation des écoulements diphasiques bioactifs dans les installations de stockage de déchets / Modeling two-phase bioactive flow in bioreactor landfills

Gholamifard, Shabnam 02 February 2009 (has links)
Accélérer la dégradation anaérobie des déchets enfouis, optimiser la production de biogaz et diminuer le temps et le coût de surveillance sont les enjeux principaux d'installation de stockage des déchets non dangereux (ISDND)-bioactives, ainsi que, plus classiquement, minimiser leurs impacts sanitaires et environnementaux. L'une des méthodes les plus efficaces pour atteindre ces objectifs est la recirculation de lixiviat et l'augmentation de l'humidité des déchets. Les objectifs du bioréacteur ne seront pas atteints sans une connaissance rationnelle des phénomènes hydrauliques, biologiques et thermiques qui s’y développent et de l’influence de l'un de ces phénomènes sur les autres. Les observations in situ, les expérimentations en laboratoire ainsi que les modèles numériques permettent ensemble une approche rationnelle de ces phénomènes. C’est ce qui constitue le corps de ce travail de thèse, où nous avons étudié le comportement hydro-thermo-biologique des déchets dans la phase anaérobie en laboratoire, sur site à partir de données hydro-thermiques de deux bioréacteurs situés en France et en développant un modèle numérique pour simuler ce comportement couplé des bioréacteurs. Les travaux en laboratoire nous ont permis d’étudier l’effet de la saturation et de la densité (compactage des déchets) sur la dégradation anaérobie des déchets ménagers et l’influence de ces paramètres sur la production de biogaz. Les données hydrauliques et thermiques in-situ des bioréacteurs nous ont permis de connaître les variations des paramètres essentiels comme la température et la saturation dans les déchets, à différentes profondeurs, et estimer d’autres paramètres qui sont difficile à déterminer expérimentalement. Le modèle numérique nous a permis d’étudier le comportement couplé, hydro-thermo-biologique, des bioréacteurs à long terme (pendant une dizaine d’années) aussi bien qu’à court terme pendant la recirculation de lixiviat. L’interdépendance des différents paramètres qui influent la dégradation des déchets est la principale raison nous ayant conduits à développer un modèle de couplage qui nous permette d'étudier chaque paramètre en fonction des autres. Les travaux en laboratoire et les données thermiques de site nous ont conduits à développer un modèle d'écoulement diphasique du liquide et du gaz dans les déchets, considérant les phénomènes biologiques, en fonction des paramètres clés de la dégradation comme la température et la saturation, pour aboutir à la production de biogaz et de chaleur. Les trois parties de ce travail, les expérimentations en laboratoire, le développement d'un modèle numérique et l’analyse des données de site ont été effectuées en parallèle de façon complémentaire. Les expérimentation de laboratoire tout comme l’analyse des données de site, nous ont montré l'importance des paramètres qu'il faut considérer dans le modèle et en retour le modèle numérique nous a aidé à diriger les expérimentations en laboratoire et montré la nécessité de conduire certaines analyses sur les pilotes expérimentaux, comme l’analyse de la biomasse, de la DCO et des AGV. L'analyse des données hydrauliques et thermiques de sites de bioréacteur nous a permis de caler les paramètres hydrauliques, biologiques et thermiques des déchets qui sont difficile à définir sur le site sans le perturber (comme la conductivité hydraulique, la saturation, la conductivité thermique, la capacité calorifique, la concentration en biomasse et en AGV). Le travail réalisé dans la thèse a permis de développer un modèle couplé hydro-thermo-biologique et de tester sa capacité à prévoir le comportement thermique d'un bioréacteur, la production totale et le taux de production de méthane. Nous avons montré qu'il était adopté à l'étude du comportement à long terme d'un bioréacteur, aussi bien qu'à court terme pendant la réinjection de lixiviat, là où les techniques de mesure et le temps sont limitants en laboratoire ou sur site / The main objectives of bioreactor landfills are to accelerate anaerobic degradation of waste in order to minimize the environmental impacts, to optimize biogas production and to minimize the time of waste stabilization as well as the costs and time of monitoring of landfill sites after operation. One of the most important and cost-effective method to achieve these objectives is liquid addition and management. The objectives of bioreactor landfills could not be achieved without enough knowledge of its hydraulic, thermal and biological parameters and processes and the effects of each of them on the others. Site observations and data and laboratory experiments as well as numerical models could help to develop the knowledge of these phenomena and processes, which is the objective of this work. In this thesis we study the coupled hydro-thermo-biological behavior of bioreactor landfills in the anaerobic phase in the laboratory and using site data of two bioreactor landfills in France and developing a numerical coupled model. The laboratory experiments help us to know the effect of such important parameters as saturation and density of wastes on anaerobic degradation and biogas production. The site data help us to know the variations of saturation and temperature of wastes in a bioreactor landfill in different depths, as two key factors of anaerobic degradation and biogas production. Site analysis helps also to estimate some parameters as hydraulic and thermal conductivity of wastes, which are hard to measure in situ without disturbing the landfill site. The numerical model helps us to study the coupled behavior of bioreactor landfills during leachate recirculation, as well as on the long term during many years. The interdependence of various parameters which influence waste degradation and thermo-biological phenomena in a bioreactor landfills is the main reason of development of this coupled model. This model makes it possible to study each key parameter, as saturation and temperature, as a function of other parameters. Laboratory experiments and site data analysis lead to develop a biological model of degradation to be coupled with a two-phase flow model of liquid and gas. The three parts of this thesis, laboratory experiments, site data analysis and development of the numerical coupled model were carried out in parallel and in a complementary manner. Laboratory experiments as well as site data analysis showed us the importance of some parameters to be considered in the numerical model and coupled behavior. In return numerical model showed the importance of considering the temperature dependence behavior of microbial activity and the necessity of biomass, VFA and COD analysis in laboratory experiments. The analysis of hydraulic and thermal site data led to estimate parameters which are hard to measure in situ or in the laboratory, as hydraulic and thermal conductivity of waste, saturation, thermal conductivity of cover layer and heat capacity of waste. The numerical coupled hydro-thermo-biological model seems to be efficient enough to predict biogas and methane production in bioreactor and classical landfills and to reproduce their correct behavior

Page generated in 0.3046 seconds