Thèses sur le sujet « URANS model »
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Durrani, Faisal. « Using large eddy simulation to model buoyancy-driven natural ventilation ». Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/12488.
Texte intégralAlam, Boulos. « Modélisation numérique de la turbulence et de la dispersion atmosphérique par faibles vents en milieu urbain ». Electronic Thesis or Diss., université Paris-Saclay, 2023. https://www.biblio.univ-evry.fr/theses/2023/interne/2023UPAST179.pdf.
Texte intégralThis thesis is situated in the context of atmospheric dispersion modeling, particularly in the presence of low winds. Atmospheric pollution sources, often located near the ground and influenced by complex obstacles, generate high concentrations of pollutants nearby, resulting in significant concentration fluctuations. Low winds, typically associated with stable atmospheric conditions, pose a specific challenge in modeling pollutant dispersion, requiring a thorough analysis of meteorological data and adaptation of prediction models. To address this complex challenge, the use of Computational Fluid Dynamics (CFD) is necessary, although further research is needed to validate its effectiveness in the near-field and in the presence of low winds. The Code_Saturne® software (EDF R&D) is selected due to its proven efficiency in simulating atmospheric pollutant dispersion. This thesis is divided into three distinct phases : the first phase focuses on the fundamentals of atmospheric dispersion, exploring the impact of various parameters such as the atmospheric boundary layer structure, atmospheric turbulence, and atmospheric stability. These elements play a crucial role in how pollutants disperse in the air. The second phase details the methodology used in Code_Saturne for conducting simulations, including the turbulence models employed and the criteria for evaluating these models. In addition to traditional isotropic models, this research investigates the use of anisotropic turbulence models to study dispersion in various contexts. The third phase of the thesis concentrates on the evaluation of different turbulence models and velocity-scalar correlations using observations conducted in urban environments under neutral and stable atmospheric conditions. Finally, the last phase of the research explores conditions of low and stable winds, typically characterized by wind speeds below 2 m/s and random wind variations. This phase examines the meandering patterns in pollutant dispersion and assesses the limitations of analytical and CFD models in predicting concentration in such conditions. To this end, a URANS model is developed and evaluated. Ultimately, a segmented Gaussian method is devised to compare the results with CFD predictions and field observations
Charrière, Boris. « Modélisation et simulation d'écoulements turbulents cavitants avec un modèle de transport de taux de vide ». Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAI108/document.
Texte intégralThe computation of turbulent cavitating flows involves many difficulties both in modeling the physical phenomena and in the development of robust numerical methods. Indeed such flows are characterized by phase transitions and large density gradients, Mach number variation due to speed of sound decrease, two-phase turbulent areas and unsteadiness.This thesis follows experimental and numerical studies led at the Laboratoire des Ecoulements Géophysiques et Industriels which aim to improve the understanding and modeling of cavitating flows. Simulations are based on a compressible code coupled with a pre-conditionning technique which handles low-Mach number areas. The two-phase flows are reproduced using a one-fluid homogeneous model and temporal discretisation is performed using an implicit dual-time stepping method . The resolution is based on the RANS approach that couples conservation equations with firts-order closure models to compute eddy viscosity.In two-phase flows areas, the computation of thermodynamic quantities requires to close the system with equations of state (EOS). Thus, two formulations are investigated to determine the pressure in the mixture. The stiffened gas EOS is written with conservative quantities while a sinusoidal law deduces the pressure from the volume fraction of vapor (the void fraction). The present study improves the homogeneous equilibrium models by including a transport equation for the void ratio. The mass transfer between phases is assumed to be proportional to the divergence of the velocity. In addition to a better modeling of convection, expansion and collapse phenomenon, this added transport equation allows to relax the local thermodynamic equilibrium and to introduce a mestastable state to the vapor phase.2D and 3D simulations are performed on Venturi type geometries characterized by the development of unstable partial cavitation pockets. The goal is to reproduce unsteadiness linked to each profile such as the formation of a re-entrant jet or the quasi-periodic vapor clouds shedding. Numerical results highlight frequency variations of unsteadiness depending on the speed of sound computation. Moreover, the simulation conducted with a relaxed vapor density increase the pressure wave propagation magnitude generated by the collapse of cavitating structures. It contributes to the destabilization of the pocket. Finally, the role of the void ratio equation is analyzed by comparing the simulation results to those obtained subsequently from a model involving only three conservation equations
Paillard, Benoît. « Simulation numérique et optimisation d'une hydrolienne à axe transverse avec contrôle actif de l'angle de calage ». Brest, 2011. http://www.theses.fr/2011BRES2069.
Texte intégralThis work describes the numerical simulation of an acti4e variable pitch Darrieus turbine with two methods, one of which is derived from momentum theory and ONERA-EDLIN unsteady model, and the other is 0Ff). Though almost no Darrieus turbine produced electrical power from wind since early 90s, a renewed interest arose from the development of water turbines because most drawbacks which prevented this system from becoming a major wind turbine system do not exist in water. For this reason many publications tackling various issues in water crossflow turbines were written in the past few years. Dynamic and static stall characteristics of an airfoil have a very strong influence on the turbine performance. Considering how the vortex method could not predict it accurately, and the complexity of a CFD simulation in an optimisation process, the ONERA-EDLIN model is a very interesting compromise. On top of that, it has the ability to model any special kinematics and not just only pitch; it can predict installed dynamic behavior based on a potential formulation; and it can calculate dynamic stall for the moments, which is interesting in the case of variable pitch. An URANS method was then used, using the solver ANSYS-CFX. The spatial and temporal discretization have been studied to be used in future simulations. Blades’ motion was obtained through mesh deformation for pitch modification, and the main rotation was implemented through global rotation of a circular mesh domain, with general grid interface model at its boundaries. The following turbulence models were used laminar, kw - SST. And Langtry Menter transition model. Five experimental cases were used to assess models’ performance. Comparison was best for kw - SST. The two others predicted early stalls, especially the laminar model. Further simulations, for other conditions and pitch function are needed and are currently being carried out. Agreement with experimental data was found to be fairly good, event though discrepancies exist in some specific cases. Agreement level could not be related to a particular operational condition. Variable pitch was implemented for a tip speed ratio of 5, aiming at performance improvement primarily. Sinusoidal functions of different orders were tested. One of them obtained a performance increase of 52%. For this regime optimal pitch variation seems to require a very slight recirculation and an incidence decrease on upwind section, and an incidence increase on downwind section. The flow deceleration through turbine was found to be a primary factor in function performance evaluation. Finally torque required to set blades into motion around their quarter chord was compared with power coefficient. Its influence was found to be close to 0, or even positive
Grondin, Julissa. « Analyse des instabilités et de la restabilisation d'un rouet centrifuge à régime partiel ». Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEC019.
Texte intégralThis work presents a numerical investigation of the aerodynamic instabilities occurring in the centrifugal compressor Turbocel, which is currently tested at the LMFA laboratory. The study aims at better understanding the mechanisms of these instabilities, as well as the mechanisms of the restabilization which is observed in the compressor at low mass flow rates and partial regime. The computational domain is restricted to the isolated impeller without the other components of the stage (Inlet Guide Vane and radial diffuser). RANS and URANS simulations are carried out on a single channel of the impeller, with the elsA solver. RANS simulations are able to capture the strong increase in impeller pressure ratio, which is observed in the tests at low flow rate. The simulations show that this increase results from a strong rise in the work transferred to the flow by the blades. This coincides with the initiation of a reversed flow zone in the impeller inducer, in the zone between the main blades and the splitter blades leading edges. The first flow particles to reverse are those coming from a stall zone on the main blade leading edge, after they have gone up to the shroud and have been transported by the tip clearance flow. This recirculation zone extends towards both the hub and the inlet when the mass flow decreases. Secondly, URANS simulations are used to characterize the unsteady flow in the impeller. Albeit restricted to a single channel, these simulations capture the existence of rotating structures in the impeller inducer, at mass flow rates which correspond to the positively-sloped part of the pressure ratio performance curve obtained from RANS results. On the other hand, in the two negatively-sloped parts of the characteristic, the field remains steady and equal to the corresponding RANS solution. The simulated rotating structures differ from classical rotating stall because their propagation is due to a convection effect by the tip flow around the circumference, rather than a mass flow repartition between the different channels. The numerical results are then validated against experimental results, and against a full-annulus simulation as well. Without external perturbation, the results of the full-annulus and isolated channel simulations remain identical during the simulated time. In the computations the presence of such rotating instabilities coincides with mass flow rate oscillations in the whole computational domain. The latter are attributed to a mechanism of rotor-stator interaction between the blades and the stall cells, due to the fact that the number of blades and the number of stall cells are equal. Moreover, when these stall cells are observed in the simulations, the average performance of the impeller is higher than the RANS performance. Illustrative results with the analytical model of Moore-Greitzer for surge and rotating stall are presented in an axial configuration. They also result in a performance which stands above the steady, underlying characteristic of the compressor. Finally, the Moore-Greitzer model proves to be unable to capture the mass flow rate oscillations which are observed in the simulations. As an outlook, this suggests to integrate the rotor-stator interaction between the rotating stall cells and the blades in the analytical model, in order to improve the fast prediction of aerodynamic instabilities in the future
Dominguez, Bermudez Favio Enrique. « Simulation numérique de parcs d'hydroliennes à axe vertical carénées par une approche de type cylindre actif ». Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAI020.
Texte intégralThe capture, thanks to hydrokinetic turbines, of the kinetic energy generated by sea and river currents provides a significant and predictable source of renewable energy. The detailed simulation, using an unsteady statistical description of URANS type, of the flow around an isolated water turbine of HARVEST type (cross flow vertical axis ducted water turbine) provides an accurate estimate of the power output. However, the cost of the URANS approach is much too expensive to be applied to a farm of several turbines. A review of the literature leads to select a low-fidelity model of Blade Element Momentum (BEM) type to describe at a reduced cost the rotor effect on the flow, in a 2D context (horizontal cross-section). The turbine performance is then predicted using a steady RANS simulation including source terms distributed within a virtual rotor ring and preserving the mesh of the turbine fixed parts (duct). These source terms are derived using an original procedure which exploits both the local flow conditions upstream of the virtual rotor cells and the flow rate through the turbine. The hydrodynamic coefficients used to compute the BEM-RANS source terms are built once for all from a series of preliminary URANS simulations; they include the effects of the duct on the flow and the rotor operating at optimal rotational speed (maximizing the power output) thanks to the turbine regulation system. The BEM-RANS model is validated against reference URANS simulations: it provides a reliable prediction for the power output (within a few % of the URANS results) at a computational cost which is lowered by several orders of magnitude. This model is applied to the analysis of the power produced by a row of Vertical Axis Water Turbines in a channel for various values of the blockage ratio and lateral spacing as well as to a 3-machine sea farm
Oliveira, Paulo Roberto de. « Modelos de urnas e loterias ». Universidade Federal de Goiás, 2014. http://repositorio.bc.ufg.br/tede/handle/tede/3960.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Many monthly, others weekly play in lottery games ignoring the randomness of the results, believing in luck or strategies that are sold to them in books about games. This monograph aims to show some concepts of probability and statistics unexplored in high school and also day to day situations that contain mathematical concepts of probability more accessible to this level of education showing some mathematical theories applied in practice games. Concepts will be discussed here: some probability distributions, their hope and variance, as well as lottery games and their probability calculations. Probability distributions will be calculated and listed in situations created from models of urns with two colors of balls, always having green as the color whose extraction will be considered successful and the red, whose extraction will be considered a failure. Now extractions with replacement balls will be made and sometimes extractions will be done without replacing them. Also, there is the case where new balls are added to both colors or one color.
Muitos jogam mensalmente, outros semanalmente, em jogos de loterias desconhecendo a aleatoriedade dos seus resultados, acreditando na sorte ou em estratégias que lhes são vendidas em livros sobre jogos. A presente monogra a tem como objetivo mostrar alguns conceitos da Probabilidade e Estatística não explorados no Ensino Médio e também situações do dia a dia que contenham conceitos matemáticos sobre Probabilidade mais acessíveis a este nível de ensino, mostrando um pouco de teorias matemáticas aplicadas na prática de jogos. Serão conceitos aqui discutidos: algumas distribuições de probabilidade, sua esperan ça e variância, além de jogos de loterias e seus cálculos de probabilidade. As distribuições de probabilidade serão enunciadas e calculadas em situações criadas a partir de modelos de urnas com duas cores de bolas, tendo sempre o verde como a cor cuja extração será considerada sucesso e, o vermelho, cuja extração será considerada insucesso. Ora serão feitas extrações com reposições das bolas e ora serão feitas extrações sem a reposição das mesmas. Também, há o caso em que serão adicionadas novas bolas de ambas as cores ou uma cor apenas.
Robertson, Francis. « An experimental investigation of the drag on idealised rigid, emergent vegetation and other obstacles in turbulent free-surface flows ». Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/an-experimental-investigation-of-the-drag-on-idealised-rigid-emergent-vegetation-and-other-obstacles-in-turbulent-freesurface-flows(07165357-67da-461d-a6a2-ed4970e2cb0c).html.
Texte intégralBedon, Gabriele. « Aero-Structural Optimization of Vertical Axis Wind Turbines ». Doctoral thesis, Università degli studi di Padova, 2016. http://hdl.handle.net/11577/3424493.
Texte intégralQuesta Tesi ha come oggetto la simulazione e l'ottimizzazione aero-strutturale di Turbine Eoliche ad Asse Verticale Darrieus. Strumenti per la simulazione aerodinamica basati su differenti tecniche sono sviluppati, migliorati rispetto allo stato dell'arte, e validati rispetto a dati sperimentali. I principali approcci considerati sono basati sui modelli Blade-Element Momentum, Vortex e Unsteady Reynolds-Averaged Navier-Stokes (URANS) Computational Fluid Dynamics (CFD) bi- e tri-dimensionali. I modelli sono sviluppati tenendo a mente l'accoppiamento con un algoritmo di ottimizzazione, quindi con particolare enfasi sullo sforzo computazionale e sulla robustezza della simulazione. Uno strumento di simulazione strutturale basato sulla teoria della trave di Eulero-Bernoulli è, in aggiunta, sviluppato e validato rispetto a dati sperimentali per effettuare una efficiente simulazione aero-strutturale. I modelli validati sono accoppiati con un algoritmo di ottimizzazione per la creazione di un ciclo per l'ottenimento di configurazioni migliorate. Differenti applicazioni sono considerate, basate sui temi di ricerca più rilevati e scenari reali. Il caso particolare di una Turbina Eolica ad Asse Verticale Troposkiana è stato considerato al fine di migliorare la configurazione aerodinamica di base di un rotore da 5 MW sviluppato nell'ambito del progetto FP7 DeepWind e di valutare le prestazioni aerodinamiche del dimostratore da 1 kW con rotore inclinato. La forma del profilo per la pala di un rotore ad H da 500 kW è oggetto anch'essa di un'attività di ottimizzazione finalizzata all'aumento della produzione aerodinamica, ottenendo una nuova geometria completamente differente da quelle disponibili in letterature. Infine, gli strumenti di simulazione aerodinamica e strutturale sono accoppiati per condurre una completa ottimizzazione aero-strutturale della forma della pala e della distribuzione di corda per un rotore Troposkiano da 500 kW. Sia la produzione aerodinamica che lo stato tensionale sono considerati come obiettivi e nuove forme palari sono individuate e discusse. I risultati della Tesi, oltre all'incremento di prestazioni rispetto alle geometrie di base, provano che i cicli iterativi, ottenuti tramite l'accoppiamento di un veloce strumento di simulazione e un algoritmo di ottimizzazione, possono essere adottati nella progettazione e test di Turbine Eoliche ad Asse Verticale Darrieus, fornendo al progettista un avanzato strumento di analisi dei fenomeni aerodinamici e strutturali agenti in queste complesse macchine.
Junior, Silvio Rodrigues de Faria. « Genotipagem de poliplóides : um modelo de urnas e bolas ». Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/45/45133/tde-08092013-214551/.
Texte intégralSince the beginnings of agriculture and livestock, the man selects individuals with desirable characteristics to breed and increase the proportion of new individuals with such qualities. With knowledge of the DNA structure and the advent of genetic engineering, the identification and characterization of individual species can make use of new technologies to help develop new varieties of plants and animals for many purposes. These technologies involve complex biochemical and physical procedures that produce even more accurated measures, like techniques that employ mass spectrometry to compare single nucleotide polymorphisms (SNPs). In plants it is common the occurrence of polyploidy, which is the presence of more than two chromosomes in the same group of homology. The determination of polyploidy level is essential for correct SNPs genotype calling and therefore greater efficiency in the study and genetic improvement of plants. In this work we characterize the phenomenon of poliploidy with probabilistic urns and balls models, proposing an efficient and appropriate method of simulation, as well as a simple technique to infer ploydy levels and classify biallelic samples accurately taking advantage of geometrical characteristics of the problem. Analysis of simulated and real data from an experiment of sugarcane were conducted with different measures of separation between groups and different experimental conditions. For the actual data, descriptive graphical methods show the correctness and consistency of the proposed method, which can be generalized to multi-allelic loci genotyping polyploid. We end our work comparing our results with the SuperMASSA [Serang2012] approach that brought excellent results to the problem. All code developed in language R were provided with the text.
Ammour, Dalila. « Highly resolved LES and tests of the effectiveness of different URANS models for the computation of challenging natural convection cases ». Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/highly-resolved-les-and-tests-of-the-effectiveness-of-different-urans-models-for-the-computation-of-challenging-natural-convection-cases(bc3e7813-b1b0-4d5b-9f27-4e50180dff59).html.
Texte intégralValdunciel, i. Coll Julio. « Paisatge i models urbans contemporanis. Les comarques gironines (1979-2006) : del "desarrollismo" a la globalització ». Doctoral thesis, Universitat de Girona, 2011. http://hdl.handle.net/10803/32044.
Texte intégralLa present Tesi doctoral conté una anàlisi quantitativa i qualitativa dels canvis en la forma i el paisatge urbans a les Comarques Gironines entre 1979 i 2006. La part teòrica situa la recerca en el marc del fenomen de la ciutat dispersa i parteix de la hipòtesi de la convergència cap a un model urbà global. La part empírica demostra aquest pressupost a través de l’estudi dels 522 plans parcials d’urbanisme aprovats durant aquest període. Els resultats permeten validar la consolidació del fenomen de la ciutat dispersa en tant que explosió de l’espai urbanitzat, difusió de la urbanització sobre el territori i aparició d’un nou paisatge cada cop més genèric, format per tres grans tipologies morfològiques: eixamples, urbanitzacions i polígons d’activitat econòmica. Tot plegat posa de manifest les carències que ha tingut el planejament per ordenar el creixement urbà, el debilitament de la ciutat com a projecte públic i una degradació del model de ciutat mediterrània.
Al-Sharif, Sharaf. « Computation of unsteady and non-equilibrium turbulent flows using Reynolds stress transport models ». Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/computation-of-unsteady-and-nonequilibrium-turbulent-flows-using-reynolds-stress-transport-models(935dbd20-b049-4b62-9e1c-eebb261675e5).html.
Texte intégralSoderquist, Daniel Robert. « Analysis of Distortion Transfer and Generation through a Fan and a Compressor Using Full-annulus Unsteady RANS and Harmonic Balance Approaches ». BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/7401.
Texte intégralAnnaduzzaman, Md. « Chitosan biopolymer as an adsorbent for drinking water treatment : Investigation on Arsenic and Uranium ». Licentiate thesis, KTH, Mark- och vattenteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-167973.
Texte intégralI många länder världen runt (även i Sverige) orsakar metallers toxicitet besvärliga vattenkvalitetsproblem och utgör ett hot mot människors hälsa. Bland de toxiska metaller som finns i svenska vatten utgör arsenik och uran i dricksvatten allvarliga hälsorisker vid långvarig exposition då de kan orsaka cancer och neurologiska problem. Flertalet brunnar är installerade i kristallint berg och sedimentära bergarter och vattnet kommer vanligen från sprickor i berggrunden. Hanteringen av sådant vatten kan kräva reduktion av expositionen för arsenik- och uraninnehåll genom förbättrade processer och teknologier. Detta är ett angeläget problem som kräver en säker, pålitlig och ekovänlig teknologi att tillämpas innan vattnet distribueras. En rad olika behandlingssystem är tillgängliga men många av dem är inte lämpliga beroende på deras höga kostnad, den komplicerade tillämpningen och problem med hanteringen av restprodukter. I denna studie has biopolymeren chitosan, den näst vanligaste polymeren efter cellulosa, konstaterats vara en möjlig adsorbent för att avlägsna arsenik(V) och uran(VI) från vatten. Karakterisering av adsorbenten har också genomförts genom XRD, FTIR, SEM, UV och strålning i synligt ljus samt TGA/DTA undersökningar. Batch-tester i bänkskala har genomförts med användning av chitosan (DDA-85%) som adsorbent för att bestämma dess förmåga att avlägsna arsenik(V) och uran(VI)genom att variera fyra parametrar, nämligen kontakttid, pH, dos av chitosan och halt av föroreningen. Adsorptionsdata vid optimala förhållanden bestämdes genom tillämpning av Langmuir, Freundlich och Dubinin-Radushkhevic (D-R) isotermerna. Vidare tillämpades Lagergrens pseudo-first-order och pseudo-second-order kinetiska modell för att undersöka adsorptionsprocessen. Karakteriseringen av materialet visade förefintligheten av effektiva amino- (N-H), hydroxyl- (O-H) samt karboxylgrupper (C=O) i chitosan-polysackariden och att det är lätt nedbrytbart. Preliminära resultat visar att reduktionen av arsenik(V) och uran(VI) var 100 respektive 97,45 % efter 300 minuters kontakttid med optimalt pH på 6,0 respektive 7,0. De optimala doserna av adsorbent och den initiala koncentrationen var 60 och 80 g/L och 100 och 250 µg/L. Adsorptions process beskrevs bäst av Freundlich-isotermen för arsenik(V) (R2 = 0.9933) och med Langmuir-isotermen för uran(VI) (R2 = 0,9858) jämfört med andra isotermer vilket var en viktig indikation på en homogen monolager-adsorption. För både arsenik(V) och uran(VI) beskrev pseudo-second order adsorptionen bättre än pseudo-first-order. Second-order kinetiska regressionskoefficienten (R2) var 0.9959 och 0.9872 respektive. De ovanstående resultaten visar sammanfattningsvis att chitosan (DDA-85%) kan användas som en billig, pålitlig och miljövänlig behandlingsmetod av vatten för arsenik(V) och uran(VI).
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Glorius, M., H. Moll, G. Bernhard, A. Roßberg et A. Barkleit. « The Mobilization of Actinides by Microbial Ligands Taking into Consideration the Final Storage of Nuclear Waste - Interactions of Selected Actinides U(VI), Cm(III), and Np(V) with Pyoverdins Secreted by Pseudomonas fluorescens and Related Model Compounds (Final Report BMBF Project No. : 02E9985) ». Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-27809.
Texte intégralBonneau, Virginie. « Prévision du bruit d'interaction tonal et à large bande d'une soufflante de nouvelle génération en régime subsonique ». Thesis, Poitiers, 2015. http://www.theses.fr/2015POIT2272.
Texte intégralModern turbofans are characterized by rotor blades with large chords, as well as heterogeneous OGV with mechanical struts integrated.The aim of this thesis is to characterize the impact of these technological innovations on sources generation and sound radiation in the bypass duct due to the interaction of the rotor wakes with the OGV. This mechanism is mainly responsible in tonal and broadband noise emissions which are dealt separately.On one hand, a URANS computation of the rotor-stator row provides the periodic sources on the heterogeneous stator as well as the sound field in the bypass duct crossed by the struts. The expansion of sound models allows to access to the tonal spectra obtained either by propagating sources thanks to a model based on the acoustic analogy principle, or by the sound field directly issued from the CFD. Then, it is shown that the stator heterogeneity induces the appearance of the fundamental tone, and that the struts lead to standing waves in the bypass duct.On the other hand, the simulation of a complete rotor channel with a ZDES approach provides the turbulent wakes. These erturbations feed an acoustic code based on the Amiet theory to predict the broadband noise radiated in the bypass duct. Despite the cost, ZDES stays clear of restrictive assumptions and sensitive calibration of isotropic homogeneous turbulence models by providing data directly workable, leading to more accurate predictions. Each of numerical simulations and acoustic predictions is validated thanks to the measurements performed in the RACE test rig
Skwarcan-Bidakowski, Alexander. « Nuclear reactor core model for the advancednuclear fuel cycle simulator FANCSEE. Advanceduse of Monte Carlo methods in nuclear reactorcalculations ». Thesis, Institutionen för Reaktorfysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-324260.
Texte intégralFANCSEE
Szubert, Damien. « Physics and modelling of unsteady turbulent flows around aerodynamic and hydrodynamic structures at high Reynold number by numerical simulation ». Phd thesis, Toulouse, INPT, 2015. http://oatao.univ-toulouse.fr/15129/2/szubert_1.pdf.
Texte intégralGlorius, M., H. Moll, G. Bernhard, A. Roßberg et A. Barkleit. « The Mobilization of Actinides by Microbial Ligands Taking into Consideration the Final Storage of Nuclear Waste - Interactions of Selected Actinides U(VI), Cm(III), and Np(V) with Pyoverdins Secreted by Pseudomonas fluorescens and Related Model Compounds (Final Report BMBF Project No. : 02E9985) ». Forschungszentrum Dresden-Rossendorf, 2009. https://hzdr.qucosa.de/id/qucosa%3A21603.
Texte intégralYe, Isaac Keeheon. « Investigation of the scalar variance and scalar dissipation rate in URANS and LES ». Thesis, 2011. http://hdl.handle.net/10012/5801.
Texte intégralPerachia, Florencia. « Estudio de la dinámica temporal de un modelo de urnas : probabilidades de primer pasaje y criticalidad auto-organizada ». Bachelor's thesis, 2020. http://hdl.handle.net/11086/15293.
Texte intégralEn este trabajo estudiamos una combinación de los clásicos modelos de urnas de Ehrenfest y del votante. En nuestro modelo, a cada paso temporal se efectúa el modelo de Ehrenfest con probabilidad α, o el del votante con probabilidad (1 − α). Este modelo puede ser visto como una caminata aleatoria unidimensional en una red finita. Analizamos los estados de equilibrio del sistema y determinamos una transición de fase para α = 1/N . Asimismo, definiendo el tamaño de avalancha como la cantidad de pasos necesarios para volver al estado de equilibrio por primera vez, estudiamos la distribuciones de tamaños de avalanchas y de retornos, para determinar si el comportamiento del sistema presenta, además, criticalidad auto- organizada. Desde el punto de vista de la sociofı́sica, este modelo representa un modelo de opinión, donde el cambio de opinión puede darse por interacción, (modelo del votante), o sin interacción, (modelo de Ehrenfest). Para valores de α relativamente chicos (∼ 1/N ), el sistema evoluciona a una sociedad polarizada.
In this work we present a combination of two classical urn models: Ehrenfest and voter . At every time step of our model either an Ehrenfest step is performed with probability \alpha or a voter step is performed with probability (1 − α). This model can be seen as an unidimensional random walk in a finite lattice. We analyzed the equilibrium states of the system and found a phase transition at α = 1/N. Furthermore, by defining the size of an avalanche as the amount of steps needed for the system to return to the equilibrium state for the first time, we studied the distribution of avalanches sizes and returns, in order to determine also if the system has Self-Organized Criticality. From the point of view of social physics this model represents an opinion model, where an agent can change its opinion by interacting with other agents (voter model) or without any interaction at all (Ehrenfest model). For relatively small α values (∼ 1 / N), the system evolves into a polarized society.
Fil: Perachia, Florencia. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía, Física y Computación; Argentina.
Klein, Markus. « Starke Korrelationen in Festkörpern : von lokalisierten zu itineranten Elektronen ». Doctoral thesis, 2009. https://nbn-resolving.org/urn:nbn:de:bvb:20-opus-36459.
Texte intégralIn this thesis angle-resolved photoemission investigations on diverse strongly- correlated systems were presented. It was shown that this technique gives a direct access to the low-energy excitations of a solid and therefore provides important information about its many-body physics. In particular the spectroscopic investigation of the sharp quasi-particle features near the Fermi edge gave information about the following points: 1. quantum phase transition: as already investigated in [27], it was shown that high resolution PES gives a direct access to the local energy scale TK. In the framework of a pertubative model, it was presented how small RKKY corrections influence the Kondo temperature. From the experimental evolution of TK(x) in CeCu6-xAux conclusions could be drawn about the quantum phase transition at T = 0. 2. Kondo lattice: an ordered CePt5/Pt(111) surface alloy was prepared and investigated by ARPES. The sharp spectra show the characteristics of a Kondo lattice: hybridization gaps and a strong renormalization of the band mass in the vicinity of the Fermi edge. With the aid of different excitation energies and measurements on an isostructural LaPt5 surface alloy it was shown, that these effects are due to a d f -mixing. For the first time, the transition from the single-impurity to the heavy-fermion regime could be observed by ARPES. 3. phase transitions: for FeSi and URu2Si2 the sensitivity of ARPES to small changes in the Fermi surface was shown in the temperature dependent spectra. The measurements reveal characteristic energies and temperatures of the phase transitions. Furthermore the bands which are involved in the phase transition and their effective masses m* could be quantified. In the case of URu2Si2 it was shown that a heavy-fermion band with m* = 40 me is affected by the hidden-order phase transition. 4. surface effects: besides CeCu6-xAux all samples showed significant surface contribution to the spectra. Excitation energy dependent measurements were found to be a good tool to distinguish between bulk and surface contributions. 5. theoretical models: despite the shared expression “strongly correlated systems” the compounds differ in their theoretical description: it was found that the physics of cerium systems (CeCu6, CePt5/Pt(111)) at T > TK can be described in the framework of the SIAM. However, at lower temperatures (T < TK) the signatures of coherence appear in the spectra. These can only be described by the PAM. Heavy dispersing bands have been observed for URu2Si2 and FeSi. Thus these systems must be described by a Hamiltonian with lattice properties, too. Especially the transition metal compound FeSi was shown to be no Kondo insulator. A description in the framework of a multi-band Hubbard Hamiltonian seems to be more appropriate for this compound