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Dissertations / Theses on the topic 'URANS model'

Author: Grafiati

Published: 7 July 2024

Last updated: 31 July 2025

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1

Durrani, Faisal. "Using large eddy simulation to model buoyancy-driven natural ventilation." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/12488.

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The use of Large Eddy Simulation (LES) for modelling air flows in buildings is a growing area of Computational Fluid Dynamics (CFD). Compared to traditional CFD techniques, LES provides a more detailed approach to modelling turbulence in air. This offers the potential for more accurate modelling of low energy natural ventilation which is notoriously difficult to model using traditional CFD. Currently, very little is known about the performance of LES for modelling natural ventilation, and its computational intensity makes its practical use on desk top computers prohibitive. The objective of th

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2

Alam, 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.

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Cette thèse se situe dans le contexte de la modélisation de la dispersion atmosphérique, en particulier en présence de vents faibles. Les sources de pollution atmosphérique, souvent situées près du sol et influencées par des obstacles complexes, engendrent des concentrations élevées de polluants à proximité, ce qui se traduit par des fluctuations significatives de ces concentrations. Les vents faibles, généralement associés à des conditions atmosphériques stables, posent un défi particulier en matière de modélisation de la dispersion des polluants, nécessitant une analyse approfondie des donné

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3

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.

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La simulation numérique des écoulements turbulents cavitants revêt de nombreuses difficultés tant dans la modélisation des phénomènes physiques que dans le développement de méthodes numériques robustes. En effet de tels écoulements sont caractérisés par un changement de phase associé à des gradients de la masse volumique, des variations du nombre de Mach causées par une chute de la vitesse du son, des zones de turbulence diphasique et la présence d'instationnarités.Les travaux de la présente thèse s'inscrivent dans la continuité des études expérimentales et numériques menées au sein du Laborat

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4

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.

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Cette thèse s’inscrit dans le contexte de la simulation d’efforts et d’écoulement dynamiques autour d’un profil en mouvement complexe dans un écoulement uniforme : la combinaison d’une rotation autour d’un axe distant et d’un tangage classique autour du quart de corde. Elle vise à mettre en place des méthodes de simulation simples de dimensionnement et de prédiction de performance d’une turbine Darrieus à contrôle actif de pas ; elle vise également à proposer une méthode de calcul permettant la simulation de l’écoulement et l’optimisation de ce type de turbine dont les pales ont leur calage qu

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5

Grondin, Julissa. "Analyse des instabilités et de la restabilisation d'un rouet centrifuge à régime partiel." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEC019.

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Ce manuscrit présente une étude numérique des instabilités aérodynamiques dans le compresseur centrifuge Turbocel, actuellement en essais au LMFA. L’étude vise à mieux comprendre les mécanismes des instabilités tournantes et de la restabilisation à bas débit observées dans le compresseur à régime partiel. L’étude est restreinte au rouet seul sans prendre en compte les autres composants de l’étage (Roue Directrice d’Entrée et diffuseur radial), au moyen de simulations RANS et URANS d'un seul canal (conditions de périodicité aux frontières latérales), à une iso-vitesse à régime partiel. Le code

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6

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.

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La récupération, grâce aux hydroliennes, de l’énergie cinétique de courants marins et fluviaux constitue une source d’énergie renouvelable considérable et prédictible. La simulation fine, par une description statistique instationnaire de type URANS, de l’écoulement autour d’une hydrolienne isolée à axe vertical, bi-rotor et munie d’un carénage (hydrolienne de type HARVEST) donne accès à une estimation précise de la puissance produite. Cependant, le coût élevé de cette approche URANS la rend inadaptée à la simulation d’un parc de machines. Une analyse de la littérature conduit à retenir un modè

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7

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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Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2015-01-27T13:45:09Z No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Dissertação - Paulo Roberto de Oliveira - 2014.pdf: 3459807 bytes, checksum: b199bab67e773541a99d42adfc9dce03 (MD5)<br>Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2015-01-28T11:28:00Z (GMT) No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Dissertação - Paulo Roberto de Oliveira - 2014.pdf: 3459807 bytes, checksum: b199bab67e773541a99d42adfc9dce03 (

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8

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.

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Vegetation is commonly modelled as emergent arrays of rigid, circular cylinders. However, the drag coefficient (CD) of real stems or trunks is closer to that of cylinders with a square cross-section. In this thesis, vegetation has been idealised as square cylinders in laboratory experiments with a turbulence intensity of the order of 10% which is similar to that of typical river flows. These cylinders may also represent other obstacles such as architectural structures. This research has determined CD of an isolated cylinder and cylinder pairs as a function of position as well as the average dr

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9

Bedon, Gabriele. "Aero-Structural Optimization of Vertical Axis Wind Turbines." Doctoral thesis, Università degli studi di Padova, 2016. http://hdl.handle.net/11577/3424493.

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This Thesis focuses on the aero-structural simulation and optimization of Darrieus Vertical Axis Wind Turbines. Aerodynamic simulation tools based on different techniques are developed, improved with respect to state-of-art tools, and validated against experimental data. The main considered approaches are based on the Blade Element Momentum, Vortex, two- and three-dimensional Unsteady Reynolds-Averaged Navier-Stokes (URANS) Computational Fluid Dynamics (CFD) models. The models are developed keeping in mind the final coupling with an optimization algorithm, therefore with particular emphasi

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10

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/.

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Desde os primórdios da agricultura e pecuária, o homem seleciona indivíduos com características desejáveis para reprodução e aumento da proporção de novos indivíduos com tais qualidades. Com o conhecimento da estrutura de DNA e o advento da engenharia genética, a identificação e caracterização de espécies e indivíduos conta com novas tecnologias para auxiliar no desenvolvimento de novas variedades de plantas e animais para diversos fins. Tais tecnologias envolvem procedimentos bioquímicos e físicos cada vez mais apurados que produzem medidas cada vez mais precisas, um exemplo disso são as técn

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11

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.

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In the present thesis turbulent natural convection of air within different challenging test cases are investigated numerically by means of an unstructured finite volume code, Code_Saturne. First, flow within both two-dimensional vertical and inclined differentially heated rectangular cavities at 60° and 15° to the horizontal for an aspect ratio of H/L=28.6 and Rayleigh number of 0.86×10e6 is computed using several high and low-Re models. Here the effectiveness of the RANS models in Code_Saturne is assessed through comparisons with a range of available experimental data. After some tests of the

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12

Valdunciel, 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.

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This doctoral thesis offers a quantitative and qualitative analysis of the changes in the urban shape and landscape of the Girona Counties between 1979 and 2006. The theoretical part of the research lies within the framework of the dispersed city phenomenon, and is based on the hypothesis of convergence towards a global urban model. The empirical part demonstrates this proposition with a study of 522 zone development plans in the Girona Counties. The results point to the consolidation of the dispersed city phenomenon, as shown by the sudden increase in built-up space, the spread of urban devel

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13

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.

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In this work the predictive capability of a number of Reynolds stress transport(RST) models was first tested in a range of non-equilibrium homogeneous flows, comparisons being drawn with existing direct numerical simulation (DNS) results and physical measurements. The cases considered include both shear and normally strained flows, in some cases with a constant applied strain rate, and in others where this varied with time. Models were generally found to perform well in homogeneous shear at low shear rates, but their performance increasingly deteriorated at higher shear rates. This was attribu

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14

Soderquist, 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.

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Understanding distortion transfer and generation through fan and compressor blade rows is able to assist in blade design and performance prediction. Using full annulus unsteady RANS simulations, the effects of distortion as it passes through the rotor of a transonic fan at five radial locations (10%, 30%, 50%, 70%, and 90% span) are analyzed. The inlet distortion profile is a 90-degree sector with a 15% total pressure deficit. Fourier distortion descriptors are used in this study to quantitatively describe distortion transfer and generation. Results are presented and compared for three operati

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15

Annaduzzaman, 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.

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In many countries over the world (including Sweden), metal toxicity in freshwater resources causes a severe drinking water quality problem and poses a threat to the environment and human health. Among the different toxic metals in the water resources of Sweden, arsenic and uranium are the biggest threats to health. These elements, over long time consumption, may even lead to cancer and/or neurological disorder. Most of the wells are installed in crystalline and sedimentary bedrock and the received water comes from water bearing fractures in the bedrock. The handling of such water is an issue a

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16

Glorius, M., H. Moll, G. Bernhard, A. Roßberg, and 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.

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The groundwater bacterium Pseudomonas fluorescens (CCUG 32456) isolated at a depth of 70 m in the Äspö Hard Rock Laboratory secretes a pyoverdin-mixture with four main components (two pyoverdins and two ferribactins). The dominant influence of the pyoverdins of this mixture could be demonstrated by an absorption spectroscopy study. The comparison of the stability constants of U(VI), Cm(III), and Np(V) species with ligands simulating the functional groups of the pyoverdins results in the following order of complex strength: pyoverdins (PYO) > trihydroxamate (DFO) > catecholates (NAP, 6HQ) > si

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17

Bonneau, 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.

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La soufflante de la nouvelle génération de moteurs Snecma est caractérisée par des pales de rotor aux bords de fuite épais, ainsi que par un OGV hétérogène intégrant les bras supports.L’objectif de cette thèse est de caractériser l’influence de ces innovations technologiques sur la génération des sources et le rayonnement sonore dans la manche secondaire liés à l’interaction du sillage du rotor avec l’OGV. Ce mécanisme est principalement responsable des émissions tonales et à large bande qui sont traitées indépendamment. D’une part, une simulation URANS de l’étage rotor-stator fournit les sour

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18

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.

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A detailed reactor core modeling of the LOVIISA-2 PWR and FORSMARK-3BWR was performed in the Serpent 2 Continuous Energy Monte-Carlocode.Both models of the reactors were completed but the approximations ofthe atomic densities of nuclides present in the core differedsignificantly.In the LOVIISA-2 PWR, the predicted atomic density for the nuclidesapproximated by Chebyshev Rational Approximation method (CRAM)coincided with the corrected atomic density simulated by the Serpent2 program. In the case of FORSMARK-3 BWR, the atomic density fromCRAM poorly approximated the data returned by the simulati

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19

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.

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This thesis aims at analysing the predictive capabilities of statistical URANS and hybrid RANS-LES methods to model complex flows at high Reynolds numbers and carrying out a physical analysis of the near-region turbulence and coherent structures. This study handles configurations included in the European research programmes ATAAC (Advanced Turbulent Simulation for Aerodynamics Application Challenges) and TFAST (Transition Location Effect on Shock Wave Boundary Layer Interaction). First, the detached flow in a configuration of a tandem of cylinders, positionned behind one another, is investigat

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20

Glorius, M., H. Moll, G. Bernhard, A. Roßberg, and 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.

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The groundwater bacterium Pseudomonas fluorescens (CCUG 32456) isolated at a depth of 70 m in the Äspö Hard Rock Laboratory secretes a pyoverdin-mixture with four main components (two pyoverdins and two ferribactins). The dominant influence of the pyoverdins of this mixture could be demonstrated by an absorption spectroscopy study. The comparison of the stability constants of U(VI), Cm(III), and Np(V) species with ligands simulating the functional groups of the pyoverdins results in the following order of complex strength: pyoverdins (PYO) > trihydroxamate (DFO) > catecholates (NAP, 6HQ) > si

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21

Ye, Isaac Keeheon. "Investigation of the scalar variance and scalar dissipation rate in URANS and LES." Thesis, 2011. http://hdl.handle.net/10012/5801.

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Large-eddy simulation (LES) and unsteady Reynolds-averaged Navier-Stokes (URANS) calculations have been performed to investigate the effects of different mathematical models for scalar variance and its dissipation rate as applied to both a non-reacting bluff-body turbulent flow and an extension to a reacting case. In the conserved scalar formalism, the mean value of a thermo-chemical variable is obtained through the PDF-weighted integration of the local description over the conserved scalar, the mixture fraction. The scalar variance, one of the key parameters for the determination of a presume

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22

Perachia, 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.

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Tesis (Lic. en Física)--Universidad Nacional de Córdoba, Facultad de Matemática, Astronomía, Física y Computación, 2020.<br>En 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

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23

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.

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In dieser Arbeit wurden mittels winkelaufgelöster Photoemission verschiedene Verbindungen mit stark korrelierten Elektronen untersucht. Es wurde gezeigt, dass diese Technik einen direkten Zugang zu den niederenergetischen Wechselwirkungen bietet und dadurch wichtige Informationen über die Vielteilchenphysik dieser Systeme liefert. Die direkte Beobachtung der scharfen Quasiteilchenstrukturen in der Nähe der Fermikante ermöglichte insbesondere die genaue Betrachtung der folgenden Punkte: 1. Quantenphasenübergang: analog zu [27] wurde gezeigt, dass die hochaufgelöste PES Zugriff auf die lokale En

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