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  • 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.
1

3-D Hydrodynamic and Non-Cohesive Sediment Transport Modeling in the Lower Mississippi River

Teran Gonzalez, Grecia A 16 May 2014 (has links)
The purpose of this research is to develop a 3-D numerical model on the Lower Mississippi River to simulate hydrodynamics and non-cohesive sediment transport. The study reach extends from Bonnet Carré Spillway (RM 127) to Head of Passes (RM 0). Delft3D with sigma coordinates was selected as the river modeling tool. This model River domain is characterized by a complex distributary system that connects the Mississippi River to the Gulf of Mexico. The boundary conditions were: water levels in the Gulf and Head of Passes; and discharges upstream. For the calibration, there are observed data for both types of boundary conditions. Several periods of high discharge were simulated to compare water level, discharge, velocity profiles and sediment transport with measurements and accomplish calibration and validation of the model. A calibrated 3-D model has been developed with the following %RMSE: 5% for stage; 6% for discharge; and 5% for sand load.
2

Toward a Molecular Mechanism of Phase Separation in Disordered Elastin-Like Proteins

Zhang, Yue 08 December 2017 (has links)
Since the last decade, an increasing number of proteins have been shown to be capable of undergoing reversible liquid-liquid phase separation (LLPS) in response to an external stimulus, and the resulting protein-rich phase (coacervate) is considered as one of the main components of membrane-less organelles. Most of these proteins are intrinsically disordered proteins (IDPs) or contain intrinsically disordered regions. More importantly, LLPS often plays an important role in cellular signaling and development of cells and tissues. However, the molecular mechanisms underlying LLPS of proteins remain poorly understood. Elastin-like proteins (ELPs), a class of IDPs derived from the hydrophobic domains of tropoelastin, are known to undergo LLPS reversibly above a concentration-dependent transition temperature (TT), allowing ELPs to be a promising thermo-responsive drug delivery vector for treating cancer. Previous studies have suggested that, as temperature increases, ELPs experience an increased propensity for type II beta-turns. Our hypothesis is that the interaction is initiated at the beta-turn positions. In this work, integrative approaches including experimental and computational methods were employed to study the early stages of ELP phase separation. Using nuclear magnetic resonance spectroscopy (NMR), and paramagnetic relaxation enhancement (PRE), we have characterized structural properties of self-association in several ELPs. NMR chemical shifts suggest that ELPs adopt a beta-turn conformation even at temperatures below the TT. The intermolecular PRE reveals there is a stronger interaction between the higher beta-turn propensity regions. Building on this observation, a series of structural ensembles were generated for ELP incorporating differing amounts of beta-turn bias, from 1% to 90%. To mimic the early stages of the phase change, two monomers were paired, assuming preferential interaction at beta-turn regions. Following dimerization, the ensemble-averaged hydrodynamic properties were calculated for each degree of beta-turn bias, and results were compared with analytical ultracentrifugation (AUC) experiments at various temperatures. The ensemble calculation reveals that accessible surface area changes dramatically as oligomers are formed from monomers with a high beta-turn content. Together, these observations suggest a model where ELP self-association is initiated at beta-turn positions, where the driving force of phase separation is solvent exclusion due to changes in the hydrophobic accessible surface area.
3

Near-wall Dynamics of Active and Passive Particles at Low Reynolds Number / 低レイノルズ領域におけるアクティブ・パッシブ粒子の壁面近傍ダイナミクス

Ohmura, Takuya 26 March 2018 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20891号 / 理博第4343号 / 新制||理||1623(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)講師 市川 正敏, 教授 山本 潤, 教授 前野 悦輝 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM
4

A 3-D Hydrodynamic Modeling at Head of Passes of the Mississippi River

Pavlyukova, Tatiana 16 May 2014 (has links)
A 3-D numerical model of the Head of Passes and Bird’s Foot Delta of the Mississippi River- was developed. The model was based on Delft3D and simulates the hydrodynamics and salinity transport for Head of Passes area from RM 6.5 to Gulf of Mexico. The model was calibrated, validated, and used to predict the response of the river to certain stimuli, such as - channel closures, channel modifications and diversions. The model includes West Bay, Southwest Pass, South Pass, Pass-A-Loutre and Main Pass. Three basic cases were developed: existing conditions, closure of Southwest Pass with a levee of 1.5m with dredging of Pass-A-Loutre to 13.7 meter depth, and closure of Southwest Pass and South Pass with dredging of Pass-A-Loutre to 13.7 meter (45 ft) depth. Salinity has been added to the model. It has been proved that salinity intrusion has a significant impact on the model instantaneous discharge. For all passes except Southwest Pass instantaneous discharge decreases almost in half. Closure of Southwest Pass and dredging of Pass-A-Loutre leads to changes in flow speed and distribution. As a result Pass-A-Loutre becomes a main River channel.
5

Estudo dos processos de admissão e exaustão utilizando ensaio experimental e simulação de um motor de combustão interna a etanol aspirado e turboalimentado / Study of intake and exhaust process using experimental test and simulation of internal combustion engine powered ethanol naturally aspirated and turbocharger

Silva, José Antônio da 27 February 2004 (has links)
O processo de admissão e exaustão exercem grande influência no desempenho de um motor a combustão interna. Vários têm sido os estudos para conhecimento e detalhamento do comportamento dos parâmetros que interferem nesses processos, nas últimas décadas. Este trabalho voltou-se principalmente para o ensaio experimental de um motor do ciclo Otto utilizando etanol como combustível, avaliando o desempenho deste motor utilizando três tipos distintos de comando de válvulas e dois coletores de admissão diferentes em sua geometria, além do uso da turbo - alimentação. Numa etapa complementar fez-se uma proposta inicial de simulação numérica do comportamento hidrodinâmico do escoamento na admissão, usando técnicas de CFD, através do software CFX. Os resultados experimentais permitiram apontar o melhor arranjo não só sob o ponto de vista de torque, potência e consumo específico, como também, o que apresentou menor índice de emissões para os gases CO, CO2, NOx, HC. Criou-se um farto banco de dados para subsidiar pesquisas em motores movidos a etanol, material escasso na bibliografia aberta. A simulação numérica apresentou concordância com alguns parâmetros medidos, mas merece ainda alguns ajustes no refinamento da malha, no tempo de simulação, e no número de ciclos ensaiados, para comprovação e maior confiabilidade nos resultados obtidos. / Intake and exhaust process exercise great influence in Internal Combustion Engine performance. The behaviour of parameters that interfere in this process have been studied in the last decades. The mainly goal of this work is to test experimentally a cycle Otto engine that use ethanol as fuel, evaluating its performance using three different types of the camshaft and two intake manifold of different geometry, besides the use of the turbocharger. In addition an initial proposal numeric simulation of the hydrodynamic flow behaviour in intake, using techniques of CFD with the software CFX was made. The experimental results allowed to aim the best arrangement of the torque, specific consumption and power and what presented lower index of emissions for the gases CO, CO2, NOx, HC. A full database was created to subsidize researches in engines powered ethanol. The numeric simulation presented agreement with some measured parameters, but it still deserves some fittings in the refinement of the mesh, in the time step of simulation and in the number of rehearsed cycles, for confirmation and larger reliability in the obtained results.
6

Αριθμητική προσομοίωση της κυκλοφορίας των υδάτων στον Πατραϊκό κόλπο

Παντίσκα, Χαραλαμπία 17 October 2007 (has links)
Στον Πατραϊκό κόλπο έχουν γίνει πλήθος ερευνητικών εργασιών με διαφορετικά αντικείμενα. Στη Φυσική Ωκεανογραφία φαίνεται να εμφανίζεται ένα ερευνητικό κενό, που αφορά την προσομοίωση της κυκλοφορίας του νερού στην περιοχή. Το κενό αυτό προσπαθεί να καλύψει η εργασία αυτή, με απώτερο σκοπό την κατανόηση του υδροδυναμικού καθεστώτος της περιοχής μελέτης. Στην εργασία χρησιμοποιούνται όλες οι υφιστάμενες βιβλιογραφικές πηγές και μετρήσεις. Επίσης χρησιμοποιείται το μαθηματικό μοντέλο ΜΙΚΕ21 για την δυσδιάστατη προσομοίωση της κυκλοφορίας του νερού αφού πρώτα προηγήθηκε η βαθμονόμηση του. Το αποτέλεσμα της εργασίας αυτής οδηγεί στην κατανόηση της δυσδιάστατης υδροδυναμικής κυκλοφορίας του νερού, κυρίως στον Πατραϊκό κόλπο αλλά και στο Στενό Ρίου – Αντιρρίου και σε ένα μικρό τμήμα του Κορινθιακού κόλπου. / In the Patras gulf they have become many of inquiring work with different objects. In the Natural Oceanography it appears that is presented an inquiring void that concerns the simulation of circulation of water in the region. This project tries to cover this void, with final aim the comprehension of hydrodynamic arrangement of region of study. In the work are used all the existing bibliographic sources and measurements. Also is used mathematic model MIKE21 for the 2-dimensions simulation of water circulation. The result of this work leads to the comprehension of 2-dimensions hydrodynamic circulation of water, mainly to the Patras gulf but also to the channel Rio-Antirio and to a small part of Corinthian gulf.
7

Estudo dos processos de admissão e exaustão utilizando ensaio experimental e simulação de um motor de combustão interna a etanol aspirado e turboalimentado / Study of intake and exhaust process using experimental test and simulation of internal combustion engine powered ethanol naturally aspirated and turbocharger

José Antônio da Silva 27 February 2004 (has links)
O processo de admissão e exaustão exercem grande influência no desempenho de um motor a combustão interna. Vários têm sido os estudos para conhecimento e detalhamento do comportamento dos parâmetros que interferem nesses processos, nas últimas décadas. Este trabalho voltou-se principalmente para o ensaio experimental de um motor do ciclo Otto utilizando etanol como combustível, avaliando o desempenho deste motor utilizando três tipos distintos de comando de válvulas e dois coletores de admissão diferentes em sua geometria, além do uso da turbo - alimentação. Numa etapa complementar fez-se uma proposta inicial de simulação numérica do comportamento hidrodinâmico do escoamento na admissão, usando técnicas de CFD, através do software CFX. Os resultados experimentais permitiram apontar o melhor arranjo não só sob o ponto de vista de torque, potência e consumo específico, como também, o que apresentou menor índice de emissões para os gases CO, CO2, NOx, HC. Criou-se um farto banco de dados para subsidiar pesquisas em motores movidos a etanol, material escasso na bibliografia aberta. A simulação numérica apresentou concordância com alguns parâmetros medidos, mas merece ainda alguns ajustes no refinamento da malha, no tempo de simulação, e no número de ciclos ensaiados, para comprovação e maior confiabilidade nos resultados obtidos. / Intake and exhaust process exercise great influence in Internal Combustion Engine performance. The behaviour of parameters that interfere in this process have been studied in the last decades. The mainly goal of this work is to test experimentally a cycle Otto engine that use ethanol as fuel, evaluating its performance using three different types of the camshaft and two intake manifold of different geometry, besides the use of the turbocharger. In addition an initial proposal numeric simulation of the hydrodynamic flow behaviour in intake, using techniques of CFD with the software CFX was made. The experimental results allowed to aim the best arrangement of the torque, specific consumption and power and what presented lower index of emissions for the gases CO, CO2, NOx, HC. A full database was created to subsidize researches in engines powered ethanol. The numeric simulation presented agreement with some measured parameters, but it still deserves some fittings in the refinement of the mesh, in the time step of simulation and in the number of rehearsed cycles, for confirmation and larger reliability in the obtained results.
8

Aplicação do modelo hidrológico SWMM na gestão das águas pluviais urbanas: estudo de caso da bacia hidrográfica do Rio Morto, Rio de Janeiro. / Application of hydrological model SWMM on urban stormwater management: a case study of the Rio Morto basin, Rio de Janeiro.

Daniele Pereira Batista Amaral 11 April 2014 (has links)
O crescimento da população e dos núcleos urbanos durante o século XX, sobretudo nos países em desenvolvimento, contribuiu para o aumento das áreas impermeáveis das bacias hidrográficas, com impactos importantes nos sistemas de drenagem urbana e na ocorrência de enchentes associadas. As enchentes trazem prejuízos materiais, na saúde e sociais. Recentemente, têm sido propostas práticas conservacionistas e medidas compensatórias, que buscam contribuir para o controle das enchentes urbanas, através do retardo do pico e amortecimento dos hidrogramas. Modelos matemáticos hidrológicos-hidráulicos permitem a simulação da adoção destas medidas de controle, demonstrando e otimizando sua localização. Esta dissertação apresenta os resultados da aplicação do modelo hidrológico Storm Water Management Model (SWMM) à bacia hidrográfica de estudo e representativa do rio Morto localizada em área peri-urbana em Jacarepaguá na cidade do Rio de Janeiro, com área de 9,41 km. O processamento do modelo SWMM foi realizado com o apoio da interface Storm and Sanitary Analysis (SSA), integrada ao sistema AutoCAD Civil 3D. Além da verificação da adequabilidade do modelo à representação dos sistemas hidrológico e hidráulico na bacia, foram desenvolvidos estudos para dois cenários como medidas de controle de enchentes: cenário 1, envolvendo implantação de um reservatório de detenção e, cenário 2, considerando a implantação de reservatórios de águas pluviais nos lotes. Os hidrogramas resultantes foram comparados ao hidrograma resultante da simulação nas condições atuais. Além disso, foram avaliados os custos associados a cada um dos cenários usando o sistema de orçamento da Empresa Rio Águas da PCRJ. Nas simulações foram adotadas a base cartográfica, e os dados climatológicos e hidrológicos previamente observados no contexto do projeto HIDROCIDADES, Rede de Pesquisa BRUM/FINEP, na qual este estudo se insere. Foram representados os processos de geração e propagação do escoamento superficial e de base. Durante o processo de calibração, realizou-se a análise de sensibilidade dos parâmetros, resultando como parâmetros mais sensíveis os relativos às áreas impermeáveis, especialmente o percentual de área impermeável da bacia (Ai). A calibração foi realizada através do ajuste manual de sete parâmetros do escoamento superficial e cinco do escoamento de base para três eventos. Foram obtidos coeficientes de determinação entre 0,52 e 0,64, e a diferença entre os volumes escoados e observados entre 0,60% e 4,96%. Para a validação do modelo foi adotado um evento pluviométrico excepcional observado na cidade em abril de 2010, que à época causou enchentes e grandes transtornos na cidade. Neste caso, o coeficiente de determinação foi igual a 0,78 e a diferença entre volumes foi de 15%. As principais distorções entre hidrogramas observados e simulados foram verificados para as vazões máximas. Em ambos os cenários as enchentes foram controladas. A partir destes estudos, pôde-se concluir que o melhor custo-benefício foi o cenário 2. Para este cenário, foi observado maiores amortecimento e retardo da vazão de pico do hidrograma, igual a 21,51% da vazão simulada para as condições atuais da bacia. Os custos de implantação orçados para os reservatórios de lote ficaram 52% a menos do que o do reservatório de detenção. / Population and urban occupation growth during 20th century, mainly in underdeveloped countries, contributed for increasing impermeable surfaces in drainage basins, leading to important impacts on urban drainage systems and associated floods. Floods cause material losses, healthy and social problems, apart of great disruptions in large citys mobility. Recently, a number of, non-conventional, conservative practices and compensatory measurements have been proposed seeking urban flood control, by lengthening hydrographs time lag and promoting shallow rising limb. Hydrologic-hydraulic mathematical models allow the simulation of these flood control measurements, demonstrating and optimizing their location, maximizing the benefits of their application. This dissertation presents the results of the application of the Storm Water Management Model (SWMM) to the representative and under study catchment of Morto River, with 9,41 km2 of area, located in a peri urban area, in Jacarepaguá, city of Rio de Janeiro, Brazil. Storm and Sanitary Analysis (SSA) tool integrated to AutoCAD Civil 3D System supported the model processing. Apart of verifying the representativeness of the hydrologic-hydraulic modelling system to the physical processes in the Morto river catchment, two different scenarios were studied as means of flood control: scenario 1, involving the simulation of one retention reservoir and, scenario 2, involving the use of multiple distributed rainwater reservoirs in the lots. The resulting hydrographs were compared to the one for catchments actual conditions. Additionally, the associated costs for each scenario were evaluated applying the official budget system of Rio Águas of Rio de Janeiro Council. It was applied the cartographic data base, climatological and hydrological data obtained in the HIDROCIDADES Project, FINEP BRUM Research Network, under which this work has been developed. The processes of generation and propagation of runoff and baseflow were modelled. During the calibration process, was performed a sensitivity analysis of the parameters, resulting as the most sensitive parameters those related to impervious areas, especially the percentage of impervious area in the basin (Ai). Manually calibration was performed, seven parameters for runoff simulation and five for baseflow were adjusted, for three events, presenting values for the coefficient of determination between 0.52 and 0.64. The difference between simulated and observed volumes varied from 0.60% to 4.96 %. Model validation was performed for an exceptional rainfall event in April 2010, which caused floods in many places in the city. In this case, the coefficient of determination was equal to 0.78 and difference in runoff volumes equal to 15 %, being identified that the main differences are in peak flows discharges. In both scenarios floods were totally controlled. It was concluded that the best cost-benefit was for scenario 2. For this scenario it was observed the best result, considering both reduction on hydrographs peak flow discharge and increasing on time to peak. Peak flow discharge was reduced by 21,51% when compared to the simulated hydrograph for catchments current stage. It was found a much lower cost for scenario 2, the budget was 52% less than the budget for scenario 1.
9

Aplicação do modelo hidrológico SWMM na gestão das águas pluviais urbanas: estudo de caso da bacia hidrográfica do Rio Morto, Rio de Janeiro. / Application of hydrological model SWMM on urban stormwater management: a case study of the Rio Morto basin, Rio de Janeiro.

Daniele Pereira Batista Amaral 11 April 2014 (has links)
O crescimento da população e dos núcleos urbanos durante o século XX, sobretudo nos países em desenvolvimento, contribuiu para o aumento das áreas impermeáveis das bacias hidrográficas, com impactos importantes nos sistemas de drenagem urbana e na ocorrência de enchentes associadas. As enchentes trazem prejuízos materiais, na saúde e sociais. Recentemente, têm sido propostas práticas conservacionistas e medidas compensatórias, que buscam contribuir para o controle das enchentes urbanas, através do retardo do pico e amortecimento dos hidrogramas. Modelos matemáticos hidrológicos-hidráulicos permitem a simulação da adoção destas medidas de controle, demonstrando e otimizando sua localização. Esta dissertação apresenta os resultados da aplicação do modelo hidrológico Storm Water Management Model (SWMM) à bacia hidrográfica de estudo e representativa do rio Morto localizada em área peri-urbana em Jacarepaguá na cidade do Rio de Janeiro, com área de 9,41 km. O processamento do modelo SWMM foi realizado com o apoio da interface Storm and Sanitary Analysis (SSA), integrada ao sistema AutoCAD Civil 3D. Além da verificação da adequabilidade do modelo à representação dos sistemas hidrológico e hidráulico na bacia, foram desenvolvidos estudos para dois cenários como medidas de controle de enchentes: cenário 1, envolvendo implantação de um reservatório de detenção e, cenário 2, considerando a implantação de reservatórios de águas pluviais nos lotes. Os hidrogramas resultantes foram comparados ao hidrograma resultante da simulação nas condições atuais. Além disso, foram avaliados os custos associados a cada um dos cenários usando o sistema de orçamento da Empresa Rio Águas da PCRJ. Nas simulações foram adotadas a base cartográfica, e os dados climatológicos e hidrológicos previamente observados no contexto do projeto HIDROCIDADES, Rede de Pesquisa BRUM/FINEP, na qual este estudo se insere. Foram representados os processos de geração e propagação do escoamento superficial e de base. Durante o processo de calibração, realizou-se a análise de sensibilidade dos parâmetros, resultando como parâmetros mais sensíveis os relativos às áreas impermeáveis, especialmente o percentual de área impermeável da bacia (Ai). A calibração foi realizada através do ajuste manual de sete parâmetros do escoamento superficial e cinco do escoamento de base para três eventos. Foram obtidos coeficientes de determinação entre 0,52 e 0,64, e a diferença entre os volumes escoados e observados entre 0,60% e 4,96%. Para a validação do modelo foi adotado um evento pluviométrico excepcional observado na cidade em abril de 2010, que à época causou enchentes e grandes transtornos na cidade. Neste caso, o coeficiente de determinação foi igual a 0,78 e a diferença entre volumes foi de 15%. As principais distorções entre hidrogramas observados e simulados foram verificados para as vazões máximas. Em ambos os cenários as enchentes foram controladas. A partir destes estudos, pôde-se concluir que o melhor custo-benefício foi o cenário 2. Para este cenário, foi observado maiores amortecimento e retardo da vazão de pico do hidrograma, igual a 21,51% da vazão simulada para as condições atuais da bacia. Os custos de implantação orçados para os reservatórios de lote ficaram 52% a menos do que o do reservatório de detenção. / Population and urban occupation growth during 20th century, mainly in underdeveloped countries, contributed for increasing impermeable surfaces in drainage basins, leading to important impacts on urban drainage systems and associated floods. Floods cause material losses, healthy and social problems, apart of great disruptions in large citys mobility. Recently, a number of, non-conventional, conservative practices and compensatory measurements have been proposed seeking urban flood control, by lengthening hydrographs time lag and promoting shallow rising limb. Hydrologic-hydraulic mathematical models allow the simulation of these flood control measurements, demonstrating and optimizing their location, maximizing the benefits of their application. This dissertation presents the results of the application of the Storm Water Management Model (SWMM) to the representative and under study catchment of Morto River, with 9,41 km2 of area, located in a peri urban area, in Jacarepaguá, city of Rio de Janeiro, Brazil. Storm and Sanitary Analysis (SSA) tool integrated to AutoCAD Civil 3D System supported the model processing. Apart of verifying the representativeness of the hydrologic-hydraulic modelling system to the physical processes in the Morto river catchment, two different scenarios were studied as means of flood control: scenario 1, involving the simulation of one retention reservoir and, scenario 2, involving the use of multiple distributed rainwater reservoirs in the lots. The resulting hydrographs were compared to the one for catchments actual conditions. Additionally, the associated costs for each scenario were evaluated applying the official budget system of Rio Águas of Rio de Janeiro Council. It was applied the cartographic data base, climatological and hydrological data obtained in the HIDROCIDADES Project, FINEP BRUM Research Network, under which this work has been developed. The processes of generation and propagation of runoff and baseflow were modelled. During the calibration process, was performed a sensitivity analysis of the parameters, resulting as the most sensitive parameters those related to impervious areas, especially the percentage of impervious area in the basin (Ai). Manually calibration was performed, seven parameters for runoff simulation and five for baseflow were adjusted, for three events, presenting values for the coefficient of determination between 0.52 and 0.64. The difference between simulated and observed volumes varied from 0.60% to 4.96 %. Model validation was performed for an exceptional rainfall event in April 2010, which caused floods in many places in the city. In this case, the coefficient of determination was equal to 0.78 and difference in runoff volumes equal to 15 %, being identified that the main differences are in peak flows discharges. In both scenarios floods were totally controlled. It was concluded that the best cost-benefit was for scenario 2. For this scenario it was observed the best result, considering both reduction on hydrographs peak flow discharge and increasing on time to peak. Peak flow discharge was reduced by 21,51% when compared to the simulated hydrograph for catchments current stage. It was found a much lower cost for scenario 2, the budget was 52% less than the budget for scenario 1.
10

An entropic approach to magnetized nonlocal transport and other kinetic phenomena in high-energy-density plasmas / Une approche entropique au transport non local et aux autres phénomènes cinétiques dans les plasmas à hautes densités d'énergie

Del Sorbo, Dario 14 December 2015 (has links)
Les simulations hydrodynamiques pour la physique de haute densité d'énergie ainsi que pour la fusion par confinement inertiel exigent une description détaillée de flux d'énergie. Le mécanisme principal est le transport électronique, qui peut être un phénoméne non local qui doit être décrit avec des modèles de Fokker-Planck, stationnaires et simplifiés dans les codes hydrodynamiques à grande échelle. Mon travail thèse est consacré au développement d'un nouveau modèle de transport non local basé sur l'utilisation d'une méthode de fermeture entropique pour la résolution des premiers moments de l'équation de Fokker-Planck agrémentée d'un opérateur de collision dédié. Une telle fermeture permet une bonne résolution des fortes anisotropies de la fonction de distribution électronique dans les régimes où le développement d'instabilités électrostatiques à petite échelle le requiert. Ce modèle aux moments (M1) est comparé avec succès au modèle de Schurtz, Nicolaï et Busquet (SNB), référent dans le domaine du transport électronique non local. Ce modèle, basé sur l'hypothèse d'une faible anisotropie de la fonction de distribution sous-jacente induisant une relation de fermeture polynomiale (P1), utilise un opérateur de collision simplifié dont nous avons proposé une amélioration. Après avoir considéré plusieurs configurations typiques de transport de chaleur, nous avons montré que le modèle M1 ultidimensionnel peut prendre naturellement en compte des effets d'un plasmas magnétisés sur le transport électronique. De plus, ce modèle permet de calculer des fonctions de distribution utiles aux études cinétiques comme la stabilité du plasma dans la zone de transport. Nous confirmons avec notre modèle que le transport d'énergie électronique peut fortement modifier l'amortissement des ondes de Langmuir et des ondes acoustiques ; contrairement aux modèles non locaux simplifiés, M1 décrit les modifications de la fonction de distribution et l'amortissement des ondes du plasma. La structure du modèle permet également de prendre en compte naturellement des champs magnétiques autogénérés, qui jouent un rôle crucial dans des simulations multidimensionnelles. Ces champs magnétiques pourraient également être étudiés pour concentrer l'énergie dans les schémas d'ignition. Enfin, nous montrons que le modèle M1 reproduit les résultats de la théorie locale élaborée par Braginskii pour tous les niveau de magnétisation et propose de nouveaux résultats pour le régime non local. Ce travail constitue une première validation de l'utilisation des fermetures entropiques, dans les régimes de faibles anisotropies, qui va s'ajouter aux tests dans les régimes fortement anisotropes. / Hydrodynamic simulations in high-energy-density physics and inertial con nement fusion require a detailed description of energy uxes. The leading mechanism is the electron transport, which can be a nonlocal phenomenon that needs to be described with quasistationary and simplified Fokker-Planck models in large scale hydrodynamic codes. My thesis is dedicated to the development of a new nonlocal transport model based on a fast-moving-particles collision operator and on a first moment Fokker-Planck equation, simplified with an entropic closure relation. Such a closure enables a better description of the electron distribution function in the limit of high anisotropies, where small scale electrostatic instabilities could be excited. This new model, so called M1, is successfully compared with the well known nonlocal electron transport model proposed by Schurtz, Nicolaï and Busquet, using different collision operators, and with the reduced Fokker-Planck model, based on a small-anisotropies polynomial closure relation (P1). Several typical configurations of heat transport are considered. We show that the M1 entropic model may operate in two and three dimensions and is able to account for electron transport modifications in external magnetic fields. Moreover, our model enables to compute realistic electron distribution functions, which can be used for kinetic studies, as for the plasma stability in the transport zone. It is demonstrated that the electron energy transport may strongly modify damping of Langmuir and ion acoustic waves, while the simplified nonlocal transport models are not able to describe accurately the modifications of the distribution function and plasma wave damping. The structure of the M1 model allows to naturally take into account self-generated magnetic fields, which play a crucial role in multidimensional simulations. Moreover, magnetic fields could also be used for the focusing of energetic particles in alternative ignition schemes. The M1 model reproduces the results of the local transport theory in plasma, developed by Braginskii, in a broad range of degrees of magnetization and predicts new results in the nonlocal regime. This work constitutes a first validation of the entropic closure assumption in the weakly-anisotropic regime. It can be added to the existing tests, in the strongly-anisotropic regimes.

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