Academic literature on the topic 'Simulation numérique de type RANS'

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Journal articles on the topic "Simulation numérique de type RANS"

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Nouri, N. M., S. M. H. Mirsaeedi, and M. Moghimi. "Large eddy simulation of natural cavitating flows in Venturi-type sections." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 225, no. 2 (June 23, 2010): 369–81. http://dx.doi.org/10.1243/09544062jmes2036.

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Large eddy simulation (LES) is used here to model the cavitating flow at a Venturi-type section. Cavitating flows can occur in a wide range of applications. The flow is represented here by means of LES, which compared to Reynolds-averaged Navier—Stokes (RANS) has the advantage that in it the large, energy-containing structures are resolved directly, whereas most of these structures are modelled in RANS. This gives LES an improved fidelity over RANS, although, due to the time averaging, the required computational time is considerably lower for RANS than for LES. The conclusion of this work shows that the qualitative comparisons with earlier preliminary data and the simulated general cavitation behaviour correlate reasonably well with experimental observations and that the simulations have the ability to predict cavitation cycle in more detail.
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Mejia, Omar, Jhon Quiñones, and Santiago Laín. "RANS and Hybrid RANS-LES Simulations of an H-Type Darrieus Vertical Axis Water Turbine." Energies 11, no. 9 (September 6, 2018): 2348. http://dx.doi.org/10.3390/en11092348.

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Nowadays, the global energy crisis has encouraged the use of alternative sources like the energy available in the water currents of seas and rivers. The vertical axis water turbine (VAWT) is an interesting option to harness this energy due to its advantages of facile installation, maintenance and operation. However, it is known that its efficiency is lower than that of other types of turbines due to the unsteady effects present in its flow physics. This work aims to analyse through Computational Fluid Dynamics (CFD) the turbulent flow dynamics around a small scale VAWT confined in a hydrodynamic tunnel. The simulations were developed using the Unsteady Reynolds Averaged Navier Stokes (URANS), Detached Eddy Simulation (DES) and Delayed Detached Eddy Simulation (DDES) turbulence models, all of them based on k-ω Shear Stress Transport (SST). The results and analysis of the simulations are presented, illustrating the influence of the tip speed ratio. The numerical results of the URANS model show a similar behaviour with respect to the experimental power curve of the turbine using a lower number of elements than those used in the DES and DDES models. Finally, with the help of both the Q-criterion and field contours it is observed that the refinements made in the mesh adaptation process for the DES and DDES models improve the identification of the scales of the vorticity structures and the flow phenomena present on the near and far wake of the turbine.
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Kissner, Carolin, Sébastien Guérin, Pascal Seeler, Mattias Billson, Paruchuri Chaitanya, Pedro Carrasco Laraña, Hélène de Laborderie, et al. "ACAT1 Benchmark of RANS-Informed Analytical Methods for Fan Broadband Noise Prediction—Part I—Influence of the RANS Simulation." Acoustics 2, no. 3 (July 22, 2020): 539–78. http://dx.doi.org/10.3390/acoustics2030029.

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A benchmark of Reynolds-Averaged Navier-Stokes (RANS)-informed analytical methods, which are attractive for predicting fan broadband noise, was conducted within the framework of the European project TurboNoiseBB. This paper discusses the first part of the benchmark, which investigates the influence of the RANS inputs. Its companion paper focuses on the influence of the applied acoustic models on predicted fan broadband noise levels. While similar benchmarking activities were conducted in the past, this benchmark is unique due to its large and diverse data set involving members from more than ten institutions. In this work, the authors analyze RANS solutions performed at approach conditions for the ACAT1 fan. The RANS solutions were obtained using different CFD codes, mesh resolutions, and computational settings. The flow, turbulence, and resulting fan broadband noise predictions are analyzed to pinpoint critical influencing parameters related to the RANS inputs. Experimental data are used for comparison. It is shown that when turbomachinery experts perform RANS simulations using the same geometry and the same operating conditions, the most crucial choices in terms of predicted fan broadband noise are the type of turbulence model and applied turbulence model extensions. Chosen mesh resolutions, CFD solvers, and other computational settings are less critical.
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Secundov, Alexander N., Stanley F. Birch, and Paul G. Tucker. "Propulsive jets and their acoustics." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 365, no. 1859 (May 22, 2007): 2443–67. http://dx.doi.org/10.1098/rsta.2007.2017.

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The complex flow physics challenges and asks questions regarding these challenges a wide range of jet flows found in aerospace engineering. Hence, the daunting task facing Reynolds-averaged Navier–Stokes (RANS) technology, for which the time average of the turbulent flow field is solved, is set out. Despite the clear potential of large eddy simulation (LES)-related methods and hybrid forms involving some RANS modelling, numerous current deficiencies, mostly related to the limitations of computational resources, are identified. It is concluded that currently, these limitations make LES and hybrids most useful for understanding flow physics and refining RANS technology. The use of LES in conjunction with a ray-tracing model to elucidate the physics of acoustic wave transmission in jets and thus improved RANS technology is described. It is argued that, as a stopgap measure, pure RANS simulations can be a valuable part of the design process and can now predict acoustics spectra and directivity diagrams with useful accuracy. Ultimately, hybrid RANS–LES-type methods, and then pure LES, will dominate, but the time-scales for this transition suggests that improvements to RANS technology should not be ignored.
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Ma, Baolong, Yujiro Ikeda, Yoshie Otake, Makoto Teshigawara, Yasuo Wakabayashi, Masahide Harada, Motoki Ooi, Takao Hashiguchi, Yutaka Yamagata, and Shin Takeda. "Slab geometry type cold neutron moderator development based on neutronic study for Riken Accelerator-driven compact Neutron Source (RANS)." EPJ Web of Conferences 231 (2020): 04004. http://dx.doi.org/10.1051/epjconf/202023104004.

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Cold neutrons with energy less than several meV are good probes for material research, and they have been available on large neutron facilities, whereas it is not commonly available on compact accelerator-driven neutron source. RIKEN Accelerator-driven Neutron Source (RANS) is a pulsed neutron facility which provides thermal neutrons and high energy neutrons at several MeV. We started a project to implement a cold neutron moderator for RANS to broaden cold neutrons applications. A cold neutron moderator system with a mesitylene moderator at 20K and a polyethylene pre-moderator at room temperature in the slab geometry was designed for RANS. So far, the thickness of the pre-moderator and mesitylene have been optimized to get the highest cold neutron flux by using a Monte Carlo simulation code, PHITS. Graphite reflector dimensions were also proven to have significant effect to increase the cold neutron intensity.
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Mahak, M., IZ Naqavi, and PG Tucker. "Cost-effective hybrid RANS-LES type method for jet turbulence and noise prediction." International Journal of Aeroacoustics 16, no. 1-2 (February 20, 2017): 97–111. http://dx.doi.org/10.1177/1475472x16684702.

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Jets at higher Reynolds numbers have a high concentration of energy in small scales in the nozzle vicinity. This is challenging for large-eddy simulation, potentially placing severe demands on grid density. To circumvent this, we propose a novel procedure based on well-known Reynolds number (Re) independent of jets. We reduce the jet Re while rescaling the boundary layer properties to maintain incoming boundary layer thickness consistent with high Re jet. The simulations are carried out using hybrid large-eddy simulation type of approach which is incorporated by using near-wall turbulence model with modified properties. No subgrid scale model is used in these simulations. Hence, they effectively become numerical large-eddy simulation with Reynolds-averaged Navier–Stokes covering the full boundary layer region. The noise post-processing is carried out using the Ffowcs-Williams-Hawking approach. The simulations are made for Mach numbers (M) of 0.75 and 0.875 (cold and hot). The results for the overall sound pressure level are observed to be within 2–3% of the measurements, and directivity of sound is also captured accurately for both the cases. Hence, the low Re simulations can be more beneficial in saving time and cost while providing reasonably accurate results.
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Lardeau, Sylvain, Ning Li, and Michael A. Leschziner. "Large Eddy Simulation of Transitional Boundary Layers at High Free-Stream Turbulence Intensity and Implications for RANS Modeling." Journal of Turbomachinery 129, no. 2 (July 14, 2006): 311–17. http://dx.doi.org/10.1115/1.2436896.

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Large-eddy simulations of transitional flows over a flat plate have been performed for different sets of free-stream-turbulence conditions. Interest focuses, in particular, on the unsteady processes in the boundary layer before transition occurs and as it evolves, the practical context being the flow over low-pressure turbine blades. These considerations are motivated by the wish to study the realism of a RANS-type model designed to return the laminar fluctuation energy observed well upstream of the location at which transition sets in. The assumptions underlying the model are discussed in the light of turbulence-energy budgets deduced from the simulations. It is shown that the pretransitional field is characterized by elongated streaky structures which, notwithstanding their very different structural properties relative to fully established turbulence, lead to the amplification of fluctuations by conventional shear-stress/shear-strain interaction, rather than by pressure diffusion, the latter being the process underpinning the RANS-type transitional model being investigated.
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Secretan, Y., M. Leclerc, S. Duchesne, and M. Heniche. "Une méthodologie de modélisation numérique de terrain pour la simulation hydrodynamique bidimensionnelle." Revue des sciences de l'eau 14, no. 2 (April 12, 2005): 187–212. http://dx.doi.org/10.7202/705417ar.

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L'article pose la problématique de la construction du Modèle Numérique de Terrain (MNT) dans le contexte d'études hydrauliques à deux dimensions, ici reliées aux inondations. La difficulté est liée à l'hétérogénéité des ensembles de données qui diffèrent en précision, en couverture spatiale, en répartition et en densité, ainsi qu'en géoréférentiation, notamment. Dans le cadre d'un exercice de modélisation hydrodynamique, toute la région à l'étude doit être documentée et l'information portée sur un support homogène. L'article propose une stratégie efficace supportée par un outil informatique, le MODELEUR, qui permet de fusionner rapidement les divers ensembles disponibles pour chaque variable qu'elle soit scalaire comme la topographie ou vectorielle comme le vent, d'en préserver l'intégrité et d'y donner accès efficacement à toutes les étapes du processus d'analyse et de modélisation. Ainsi, quelle que soit l'utilisation environnementale du modèle numérique de terrain (planification d'aménagement, conservation d'habitats, inondations, sédimentologie), la méthode permet de travailler avec la projection des données sur un support homogène de type maillage d'éléments finis et de conserver intégralement l'original comme référence. Cette méthode est basée sur une partition du domaine d'analyse par type d'information : topographie, substrat, rugosité de surface, etc.. Une partition est composée de sous-domaines et chacun associe un jeu de données à une portion du domaine d'analyse par un procédé déclaratoire. Ce modèle conceptuel forme à notre sens le MNT proprement dit. Le processus de transfert des données des partitions à un maillage d'analyse est considéré comme un résultat du MNT et non le MNT lui-même. Il est réalisé à l'aide d'une technique d'interpolation comme la méthode des éléments finis. Suite aux crues du Saguenay en 1996, la méthode a pu être testée et validée pour en démontrer l'efficacité. Cet exemple nous sert d'illustration.
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Mnasri, Aida, and Ezzeddine Hadj Taieb. "Simulation numérique par éléments finis des écoulements transitoires à surface libre." La Houille Blanche, no. 5-6 (December 2019): 81–92. http://dx.doi.org/10.1051/lhb/2019032.

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Une simulation numérique par des éléments finis des écoulements transitoires à surface libre dans les canaux prismatiques est présentée. Dans cette étude, l'écoulement est supposé unidirectionnel dans un canal de faible pente. Le modèle mathématique est constitué d'un système de deux équations aux dérivées partielles de type hyperbolique résolu numériquement par la méthode des éléments finis. Pour définir les fonctions d'interpolation dans la forme intégrale des résidus pondérés, la méthode de Galerkin a été utilisée. Dans les applications, différentes sections prismatiques sont examinées. Les régimes transitoires étudiés sont dus à des manœuvres de vanne placée en aval du canal, l'extrémité amont étant connectée à un réservoir de niveau constant. Dans ces conditions, le régime transitoire correspond à une évolution de l'écoulement d'un régime permanent initial vers un régime permanent final. Ces deux régimes sont supposés uniformes à débit constant défini par la formule de Manning. Les résultats obtenus concernent l'évolution des paramètres hydrauliques en différentes sections du canal, suite à la manœuvre en aval. Deux cas de manœuvres sont considérés ; le cas d'une ouverture et le cas d'une fermeture. L'étude a permis d'analyser la propagation des ondes de surface et la réflexion de ces ondes sur les deux extrémités du canal. En particulier, les résultats numériques montrent que lorsque la largeur du lit du canal est très petite (cas de la section triangulaire), les fluctuations des profondeurs sont rapidement amorties.
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Davidson, Josh, and Ronan Costello. "Efficient Nonlinear Hydrodynamic Models for Wave Energy Converter Design—A Scoping Study." Journal of Marine Science and Engineering 8, no. 1 (January 11, 2020): 35. http://dx.doi.org/10.3390/jmse8010035.

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This review focuses on the most suitable form of hydrodynamic modeling for the next generation wave energy converter (WEC) design tools. To design and optimize a WEC, it is estimated that several million hours of operation must be simulated, perhaps one million hours of WEC simulation per year of the R&D program. This level of coverage is possible with linear potential flow (LPF) models, but the fidelity of the physics included is not adequate. Conversely, while Reynolds averaged Navier–Stokes (RANS) type computational fluid dynamics (CFD) solvers provide a high fidelity representation of the physics, the increased computational burden of these models renders the required amount of simulations infeasible. To scope the fast, high fidelity options, the present literature review aims to focus on what CFD theories exist intermediate to LPF and RANS as well as other modeling options that are computationally fast while retaining higher fidelity than LPF.
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Dissertations / Theses on the topic "Simulation numérique de type RANS"

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Leveugle, Benoît. "Simulation DNS de l’interaction flamme-paroi dans les moteurs à allumage commandé." Thesis, Rouen, INSA, 2012. http://www.theses.fr/2012ISAM0021/document.

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Dans le cadre du projet INTERMARC (INTERaction dans les Moteurs à Allumage Commandé), la tâche du CORIA a consisté à produire une base de données à l'échelle RANS (provenant de données DNS) afin de tester, valider et modifier le modèle d'interaction développée par IFPen. Ce modèle vise l'ajout d'une composante d'interaction, phénomène non pris en compte par les lois de paroi actuelles.Ce projet repose sur l'interaction forte entre les différents protagonistes présents. Le CORIA et le CETHIL ont travaillé ensemble à la réalisation d'une base de données pour tester les modèles initiaux proposés par IFPen, puis en fonction des résultats obtenus, à itérer avec IFPen pour modifier et améliorer les modèles. Ces tests ont inclus des simulations 2D laminaires, 2D turbulentes, et 3D turbulentes
Under the INTERMARC project (Flame wall interaction in spark ignition engines), CORIA's job was to produce a database to RANS scale (from DNS data) to test, validate and modify the interaction model developed by IFPEN. This model aims the addition of the interaction phenomena, non-captured by the current wall laws. This project is based on the strong interaction between the different actors. The CORIA and the CETHIL have worked together in the creation of the database, where the experimental data were also used to validate the resuslts of the DNS code.CORIA then used this database to test the original model proposed by IFPPEN, then according to the results obtained, CORIA iterated with IFPEN to modify and improve the models. These tests included laminar 2D simulations, 2D turbulent and 3D turbulent simulations
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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 modèle basse-fidélité de type Blade Element Momentum (BEM) pour décrire à moindre coût l’effet du rotor de la turbine sur l’écoulement, dans le contexte d’une description 2D (coupe horizontale). La performance de l’hydrolienne est alors prédite par un calcul RANS incluant des termes sources distribués dans un anneau rotor virtuel et conservant le maillage des parties fixes (carénage). Ces termes sources sont construits grâce à une procédure originale exploitant les conditions locales de l’écoulement en amont des cellules du rotor virtuel et le débit de l’écoulement traversant l’hydrolienne. Les coefficients hydrodynamiques utilisés pour le calcul des termes sources BEM-RANS sont construits une fois pour toutes en exploitant une série de simulations URANS préliminaires ; ils intègrent les effets du carénage et le fonctionnement de chaque rotor à une vitesse de rotation optimale (maximisant la puissance produite) grâce au système de régulation de l’hydrolienne. Le modèle BEM-RANS développé est validé par comparaison avec des simulations URANS de référence : il fournit une estimation fiable de la puissance produite (erreur de quelques % par rapport à l’approche URANS) pour un coût réduit de plusieurs ordres de grandeur. Ce modèle est appliqué à l'analyse de la puissance produite par une rangée d’hydroliennes HARVEST dans un canal pour différents facteurs de blocage et d’espacement latéral ainsi qu’à une ferme marine composée de trois hydroliennes
The 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
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Leveugle, Benoît. "Simulation DNS de l'interaction flamme-paroi dans les moteurs à allumage commandé." Phd thesis, INSA de Rouen, 2012. http://tel.archives-ouvertes.fr/tel-00845226.

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Dans le cadre du projet INTERMARC (INTERaction dans les Moteurs à Allumage Commandé), la tâche du CORIA a consisté à produire une base de données à l'échelle RANS (provenant de données DNS) afin de tester, valider et modifier le modèle d'interaction développée par IFPen. Ce modèle vise l'ajout d'une composante d'interaction, phénomène non pris en compte par les lois de paroi actuelles.Ce projet repose sur l'interaction forte entre les différents protagonistes présents. Le CORIA et le CETHIL ont travaillé ensemble à la réalisation d'une base de données pour tester les modèles initiaux proposés par IFPen, puis en fonction des résultats obtenus, à itérer avec IFPen pour modifier et améliorer les modèles. Ces tests ont inclus des simulations 2D laminaires, 2D turbulentes, et 3D turbulentes.
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Bodoc, Virginel. "Modélisation de l'évaporation de gouttes multicomposants." Toulouse, ISAE, 2011. http://www.theses.fr/2011ESAE0022.

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L’objectif de cette thèse a été d’étudier l’évaporation d’un brouillard multi-composant à l’aide d’approches expérimentale et numérique. Deux axes de recherche ont été privilégiés. Une base de données expérimentales a tout d’abord été créée en utilisant différentes techniques optiques de mesure. Une attention particulière a été accordée à la technique Arc-en-Ciel Global (ACG), utilisée pour la mesure de la température des gouttes. Ensuite des simulations numériques ont été réalisées pour des brouillards mono et bi-composant en évaporation. Dans la première phase de cette recherche, les investigations expérimentales et numériques ont été conduites pour un brouillard polydisperse, non-confiné et en refroidissement. Cette configuration offre l’avantage de pouvoir étudier l’évaporation sous une faible influence de la phase gazeuse. Pour un liquide bicomposant, l’effet de la variation de concentration sur les mesures ACG a été analysé à l’aide d’un couplage entre la technique expérimentale et la simulation numérique. Après avoir validé les modèles d’évaporation sur le brouillard non-confiné, une configuration plus complexe se rapprochant des conditions réelles d’une chambre de combustion a été étudiée (montage IMFT). En ce qui concerne la simulation numérique, la phase gazeuse a été caractérisée en utilisant une approche de type LES. La phase dispersée constituée des gouttes mono-composant est prise en compte dans le calcul. La nature très instationnaire de l’écoulement diphasique a été mise en évidence. La comparaison entre l’expérience et la simulation numérique a permis d’évaluer l’intérêt de la technique ACG pour la mesure de la température des gouttes
The objective of this thesis was to study the vaporization of a multicomponent spray with both experimental and numerical approaches. To achieve this objective, the effort was guided in two directions. Firstly, an experimental database has been created using different optical measurement techniques. A special attention was focused onto the application of Global Rainbow Refractometry (GRR), used for the measurement of droplets temperature. Secondly, numerical simulations were performed for mono and bi-component sprays in evaporation. In the first part of this study, experimental and numerical tests were carried out on a polydisperse nonconfined and cooling spray. This configuration was adopted because it allows the study of the vaporization with a reduced influence from the gaseous phase. For a bi-component liquid, the effect of the composition variation on the GRR measurements was analysed within a coupling between the experimental technique and the numerical simulation. In the second part, experimental investigations and numerical simulation were performed for a more complex configuration that consists in a spray evolving in a heated and confined medium. The gaseous phase was computed with a LES approach while the dispersed phase, always mono-component, was solved with a Lagrangian tracking approach. The unsteady nature of the flow was demonstrated and the interest of the GRR technique for the droplets temperature measurement was proved
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Bonnifet, Valentin. "Prédiction du phénomène de tremblement sur un profil d'aile avec une approche LES de type PANS-RSM." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS389.

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L'objectif de cette étude est le developpement d'un modèle de sous-maille à équations de transport pour la simulation aux grandes échelles. Le modèle de sous-maille est développé par analogie avec le modèle statistique du second ordre proposé par Gerolymos-Lo-Vallet-Younis. Un paramètre de contrôle constant y est introduit afin de régler la quantité d'énergie cinétique turbulente modélisée par le modèle de sous-maille. Ce paramètre permet un passage continue entre la résolution directe et statistique des équations de Navier-Stokes. Cette approche à la capacité de prédire correctement des écoulements turbulents avec un maillage spatio-temporel plus grossier qu'avec l'approche de la simulation au grandes échelles classique utilisant des modèles de sous-maille algébriques. La méthode proposée est utilisée pour simuler un écoulement transsonique autour du profil d'aile OAT15A. Pour les conditions d'entrées étudiées, cet écoulement est le siège d'une interaction onde de choc couche limite turbulente sur l'extrados du profil d'aile provoquant une oscillation auto-entretenue de la position de l'onde de choc. Les résultats montrent que l'approche développée est apte à reproduire le mouvement de l'onde de choc. Une analyse des grandeurs filtrées de l'écoulement, des corrélations turbulentes ainsi que de l'impact du paramètre de contrôle est présentée. Enfin, cette étude énonce des suggestions de développement pour améliorer le modèle de sous-maille proposé en utilisant un paramètre de contrôle inhomogène en espace et/ou en temps
This PhD was devoted to develop a Large Eddy Simulation subgrid scale model based on transport equations. The subgrid scale model is built in the same manner as second order statistical model suggested by Gerolymos-Lo-Vallet-Younis. A constant control parameter has been introduced to tune the amount of turbulent kinetic energy handled by subgrid scale model. This parameter allows a bridging from Direct Numerical Simulation to Reynolds Averaged Navier-Stokes. This approach can correctly predict turbulent flow with coarser grid and time step than canonical Large Eddy Simulation based on algebraic subgrid scale models where subgrid length scale corresponds to Taylor micro scale. Indeed, the subgrid scale model handles a large part of turbulent kinetic energy in the boundary layer.Transonic flow simulation around OAT15A airfoil is carried out using the suggested approach. On particular inflow conditions, the shock-wave shows a self-sustained motion on the airfoil upper side resulting from the shock-wave boundary layer interaction. Reynolds Averaged Navier-Stokes is not able to predict averaged field because this large unsteadiness is undeterministic and an LES approach is needed. According to the results, the suggested approach can handle shock-wave motion. Filtered flow field, turbulent correlation and control parameter impact analysis are presented. Finally, development ways are suggested in order to improve the subgrid scale model using inhomogeneous control parameter in space and/or time
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Troadec, François. "Simulation numérique directe d'un écoulement supercritique pour validation des approches RANS et LES." Rouen, 2010. http://www.theses.fr/2010ROUES043.

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Le travail effectué au cours de cette thèse a été de développer et implémenter des outils capables d’aider à la simulation numérique d’écoulements cryogéniques, en proposant des cas-tests basés sur des expériences «numériques» via l’utilisation de la Simulation Numérique Directe (DNS). Les problèmes rencontrés au cours des différentes expériences, dus aux conditions d’utilisation (une pression supérieure à 50 Bar et des réactifs très inflammables), amènent donc les industriels à développer de nouveaux outils numériques. En effet, au delà d’une certaine pression, la distinction entre la phase liquide et la phase gazeuse disparaît et les interactions intermoléculaires ne peuvent plus être négligées ce qui affecte les mécanismes de transport. Différents modèles de la littérature ont été étudiés et comparés à des données de référence (NIST). Certains ont ensuite été introduits dans le code de simulation Asphodèle, basé sur une formulation bas nombre de Mach. La configuration étudiée permet de simuler la déstabilisation d’un jet en condition supercritique. L’objectif principal étant de se rapprocher au plus près des conditions réelles de fonctionnement et de tester la formulation bas nombre de Mach utilisée pour la première fois en écoulement supercritique. Enfin, disposant de résultats issus d’une simulation numérique directe, nous avons évalué, à partir de tests a priori, la pertinence de modèles utilisées dans certaines simulations supercritiques RANS ou LES, tel le modèle de variable de mélange ou l’utilisation des variables filtrées dans l��équation d’état
The main aim of this work is to develop tools able to realise numerical simulation of cryogenic flows by proposing tests case based on numerical experiments through the use of Direct Numerical Simulation (DNS). Many problems encountered during experiments are due to experimental conditions (high pressure and very flammable reactives) that impose researchers to consider new numerical ways. Indeed, beyond a given pressure, the distinction between liquid and gaseous phase disappears and molecular interactions can’t be neglected anymore. This affects thermo-physical variables. So, different physical models have been studied and results have been compared to reference data (NIST). Some of them have been introduced in Asphodele solver. This solver is based on a low Mach number formulation. The reference configuration used simulates the destabilization of a jet in supercritical condition. Main aim being to reach conditions present inside the rocket’s combustion chamber and to test low Mach number formulation applied in supercritical flows. Finally, from results extracted from DNS simulation, a priori tests are used to study RANS and LES terms modelisation like the mixture fraction formulation (RANS) and the use of filtered variable in equation of state (LES)
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7

Léonard, Thomas. "Étude des approches de modélisation de la turbulence pour la simulation numérique d’un compresseur centrifuge à fort taux de pression." Thesis, Toulouse, ISAE, 2014. http://www.theses.fr/2014ESAE0029/document.

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Cette étude a pour objectif d’étudier différentes approches de modélisation de la turbulence sur un compresseur centrifuge industriel à fort taux de pression afin d’essayer d’élargir notre compréhension des différents phénomènes physiques mis en jeu et leur interaction avec la turbulence. D’abord, la sensibilité au maillage et au modèle turbulence est évalué sur des calculs RANS. Une analyse de simulations LES est ensuite effectuée. En particulier, une étude de l’effet de la turbulence sur l’écoulement et une comparaison aux résultats RANS et expérimentaux est réalisée. Enfin, deux approches hybrides DES sont étudiées afin d’exposer les problèmes rencontrés par ces modèles sur cette configuration. Il en résulte une évaluation des différentes méthodes et de leur applicabilité future dans un contexte industriel
This study aims to assess the abilities of existing numerical simulation methods to predict the complex physical phenomena occurring in an industrial centrifugal compressor and especialy the effect of turbulence on the different flow features. RANS simulations are first performed using various turbulence model, then LES simulations and finally, two simulations using RANS/LES hybrid models of DES type are carried out. The whole compressor operating range is simulated using RANS, but because of LES and DES high computational costs, attention is focussed on the nominal operating point. Particular care is devoted to determine the impact of grid refinement on the simulation results. To this end, simulations are performed on three grids, respectively composed of over 8, 26 and 165 million cells. Even though the grids used do not fulfill the mesh refinement criteria recommended in the litterature for an accurate wall-resolved LES simulation, the simulation performed on the denser grid provides interesting conclusions on the turbulence generation and its interaction with the mean flow.The hybrid DES approches used involve a shield function to prevent the boundary layers to be computed in LES. However, this function is found to be unsuited to this centrifugal compressor flow. Indeed, the RANS and LES regions are not correctly located and most of the tip leakage flow is resolved using a RANS approach, preventing the development of turbulence.This work allowed us to evalute the various approches and highlight some of the problems and advantages of each for the simulation of this centrifugal compressor
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8

Monroy, Charles. "Simulation numérique de l'intéraction houle-structure en fluide visqueux par décomposition fonctionnelle." Ecole centrale de Nantes, 2010. http://www.theses.fr/2010ECDN0033.

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La décomposition fonctionnelle dans les équations de Navier-Stokes est un artifice mathématique tirant profit du fait que les échelles des phénomènes associés respectivement à la propagation de la houle et à l'évolution du champ diffracté ( et radié) par un corps sont nettement disctinctes. Les inconnues principales du problèmes sont divisées en une partie incidente représentant la propagation de la houle et une partie diffractée représentant la perturbation due à la présence du corps flottant ou immergé. Cette décomposition est alors introduite dans les équations de Navier-Stokes moyennées au sens de Reynolds. Les termes incidents sont obtenus explicitement sur un modèle de houle incidente en théorie potentielle non-linéaire (plus précisément par une méthode spectrale) et les termes diffractés sont déterminés par la résolution des équations RANS ainsi modifiées. La génération de la houle incidente étant réalisée par un modèle en théorie potentielle, le temps de calcul associé est très faible, la qualité de propagation est optimale et la gamme de houles envisageables est très importante. Cet avantage est combiné à une résolution globale de l'écoulement qui reste néanmoins sous l'hypothèse de fluide visqueux. Ce travail de tehèse constitue une contribution au développement de la méthode SWENSE (Spectral Ware Explicit Navier-Stokes Equations) et propose plusieurs cas de validation en houle régulière aussi bien qu'en houle irrégulière. Les limitations de la méthode sous sa forme actuelle, en particulier la problématique liée à la gestion du déferlement, sont discutées et des réponses pour y faire face sont suggérées
Functional decomposition in the Navier-Stokes equations is a mathematical tool with takes advantage of the fact that the swell propagation and the evolution of the diffracted field from a body are two phenomena with different spatial scales. The principal unknowns of the problem are divided into an incident part representing the swell propagation and a diffracted part representing the perturbation due to the presence of the floating or submerged body. This decomposition is then introduced in the Reynolds-averaged Navier-Stokes equations. Potential flow theory (more precisely spectral methods) is used to compute the incident waves while viscous effects are taken into account by using a modified RANSE solver to obtain the diffracted field in the full domain. By using this approach it is possible to simulate various nonlinear incident waves in an efficient and accurate manner: regular wave trains, focused waves, irregular 2D or 3D sea states. The present work is a contribution to the developent of the SWENSE (Spectal Ware Explicit Navier-Stokes Equations) method and offers several validation cases in regular sea as well as in irregular sea. The limitations of the method in its current form are discussed, especially the over-breaking problem, and answers to them are provided
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Marzouk, Salwa. "Simulation numérique d'un écoulement de type jet pulsé." Aix-Marseille 2, 2002. http://www.theses.fr/2002AIX22078.

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Bentaleb, Yacine. "Modélisation et simulation numérique de la turbulence par des approches statistiques bas-Reynolds et hybride Rans/Les." Pau, 2007. http://www.theses.fr/2007PAUU3028.

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Le travail présenté dans cette thèse s'inscrit dans le contexte de la modélisation et de la simulation numérique des écoulements turbulents à grand nombre de Reynolds, avec intégration des équations jusqu'à la paroi. L'objectif principal est de reconsidérer les approches existantes de la turbulence, en s'appuyant sur des outils numériques récents, afin d'obtenir des résultats plus précis sur des maillages non-structurés, notamment en proche paroi. Dans la perspective d'une hybridation avec l'approche LES, nous étudions tout d'abord les performances d'un modèle k-ε bas-Reynolds linéaire. Nous le comparons ensuite à une extension non-linéaire cubique qui permet de tenir compte de l'effet d'anisotropie. Le solveur Navier-Stokes compressible utilise une approche mixte éléments/volumes finis instationnaire implicite. Dans deux cas d'écoulements stationnaires nous obtenons des résultats satisfaisants avec le modèle linéaire, alors que l'extension non-linéaire montre une forte sensibilité au paramètre de viscosité turbulente Cµ. Dans le cas instationnaire, le modèle non-linéaire s'est montré bien plus performant. Nous proposons ensuite une combinaison originale entre les approches de type RANS et LES. L'idée de base consiste à résoudre le champ moyen par les équations de type RANS, puis à le corriger en ajoutant les fluctuations résolues par l'approche VMS (Variational Multi-Scale) de la LES. Le terme de correction est amorti par une fonction d'hybridation continue à travers le domaine de calcul. Le modèle obtenu est appliqué à l'écoulement 3D autour d'un cylindre circulaire à séparation turbulente. Nous analysons les différentes régions de l'écoulement ainsi que sa topologie
The work presented in this thesis concerns the turbulence modelling and numerical prediction of high Reynolds number flows by performing the integration of the governing equations up to the wall. The main objective is to reconsider existing turbulence models, using recent numerical tools, in order to obtain more accurate results on unstructured meshes, particularly in the near-wall region. In the perspective of hybridisation with a LES approach, we study first a linear low-Reynolds k-ε model. Then, we compare it with a cubic eddy-viscosity model, which allows accounting for anisotropy effect. The compressible Navier-Stokes solver uses an implicit unsteady mixed finite element/volume method. In two steady flow cases (turbulent channel and backward-facing step flows), we obtain satisfactory results with the linear model, whereas the nonlinear extension shows a substantial sensitivity to the eddy-viscosity parameter Cµ. In the unsteady flow (circular cylinder), the nonlinear model shows higher performances. Next, we propose a novel combination of RANS and LES approaches. The basic idea is to solve the averaged flow field by the RANS equations, and to correct it by adding the remaining resolved fluctuations with VMS (Variational Multi-Scale) approach of LES. The correction term is damped by a smooth blending function across the computational domain. The obtained model is applied to a three-dimensional flow past a circular cylinder with turbulent separation. We analyse the different flow regions and the flow topology. The statistics computed from numerical simulations are consistent with the experimental data and the hybrid approach of DES-type
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Conference papers on the topic "Simulation numérique de type RANS"

1

Yao, Jixian, Steven E. Gorrell, and Aspi R. Wadia. "High-Fidelity Numerical Analysis of Per-Rev-Type Inlet Distortion Transfer in Multistage Fans: Part II—Entire Component Simulation and Investigation." In ASME Turbo Expo 2008: Power for Land, Sea, and Air. ASMEDC, 2008. http://dx.doi.org/10.1115/gt2008-50813.

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Part I of the paper validated the ability of the Unsteady RANS solve Pturbo to accurately simulate distortion transfer and generation through selected blade rows of two multistage fans. In part II, unsteady RANS calculations were successfully applied to predict the one-per-rev inlet total pressure distortion transfer in the entirety of two differently designed multistage fans. This paper demonstrates that Hi-Fi CFD can be used early in the design process for verification purposes before hardware is built, and can be used to reduce the number of distortion tests, hence reducing engine development cost. The unsteady RANS code Pturbo demonstrated remarkable agreement with data, accurately capturing both the magnitude and profile of total pressure and total temperature measurements. Detailed analysis of the flow physics identified from the CFD results has led to a thorough understanding of the total temperature distortion generation and transfer mechanism, especially for the spatial phase difference of total pressure and total temperature profiles. The analysis illustrates that the static parameters are more revealing than their stagnation counterpart and that pressure and temperature rise are more revealing while the pressure and temperature ratio could be misleading. The last stage is effectively throttled by the inlet distortion even though the overall engine throttle remains unchanged. The total temperature distortion generally grows as flow passes through the fan stages.
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Spencer, Adrian, and Virgil Adumitroaie. "Large Eddy Simulation of Impinging Jets in Crossflow." In ASME Turbo Expo 2003, collocated with the 2003 International Joint Power Generation Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/gt2003-38754.

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Large Eddy Simulations and RANS predictions have been carried out for a generic primary zone type jet configuration, for which significant LDA experimental data is available. It consists of an annular passage feeding a row of ports that issue jets into a confined crossflow. A bleed flow of 50% past the ports in the feed annulus and a jet to cross flow ratio of 5 are set-up in order to be representative of annulus fed primary jets. Time averaged inlet boundary conditions have been taken from experimental data and have had time-correlated fluctuations with the correct RMS values and time scales imposed on them. Calculations have been performed on a modest PC cluster using the CFD-ACE+ flow solver package. Results show that LES is able to surpass RANS quantitatively and qualitatively. At the time-average impingement point of the jets the LES predicted normal stresses are in considerably better agreement with experimental data than is RANS, which is to be expected considering the limitations of k-ε models relying upon linear stress-strain relationships. Phenomena impossible to capture using RANS are also well predicted by LES, such as bimodal pdf’s that have been witnessed at the time average stagnation point where the cross flow and jet back flow meet. By solving for a conserved scalar it has also been possible to examine mixing rates within the recirculation zone.
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3

Yamamoto, Makoto. "Proposal of a RANS Model to Predict Both K- and D-Type Roughness." In ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/fedsm2003-45349.

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The effect of surface roughness on the aerodynamic performance of a blade and an airfoil is one of very important issues in aeronautic and mechanical engineering. Since existing turbulence models were developed for uniformly distributed roughness, the availability would be limited under a certain flow and roughness conditions. Considering a blade surface with ice accretion, foreign object damage and erosion, the roughness is not uniformly distributed, but isolated or local. Therefore, in such a multi-physics simulation, it is needed to develop a more universal turbulence model to predict the flow fields around a blade with various types of surface roughness. In the present study, employing the virtual force that represents the effect of each roughness element on the mean flow field, I develop and verify a new k–ε turbulence model that can be successfully applied to both k- and d-type roughness.
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Perez, Ethan, John T. Schmitz, Nicholas A. Jaffa, Aleksandar Jemcov, Joshua D. Cameron, and Scott C. Morris. "Detailed Experimental Measurement and RANS Simulation of a Low Pressure Turbine With High Lift Blading." In ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-91820.

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Abstract The aerodynamic characteristics of high–lift airfoil designs is of interest for improved performance and reduced blade count in Low–Pressure Turbine (LPT) design. The present paper presents both experimental measurements as well as numerical simulation results from a single-stage LPT. The airfoils were designed for an embedded stage with a total pressure expansion ratio of 1.75 and a rotor Zweifel coefficient of 1.35. The measurement program was highly unique in that detailed measurements were obtained using a variety of different probe types, including time–resolved total pressure and hot–wires. Agreement between various measurement types was generally good, but differences beyond typically stated uncertainty bounds were noted. The computations were done using RANS and a mixing model via commercially available software. The numerical results were evaluated to determine the efficacy of this type of model for prediction and design of high–lift airfoils. The computations agreed very well with the experimental results in the midspan region, but losses were over–predicted in the lower 40% span near the hub. A basic description and understanding of the flow physics in the LPT stage are presented based on the relative agreement between the experiments and computations.
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Jamal, Tausif, and D. Keith Walters. "A Dynamic Time Filtering Technique for Hybrid RANS-LES Simulation of Non-Stationary Turbulent Flow." In ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/ajkfluids2019-4696.

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Abstract Unsteady turbulent wall bounded flows can produce complex flow physics including temporally varying mean pressure gradients, intermittent regions of high turbulence intensity, and interaction of different scales of motion. As a representative example, pulsating channel flow presents significant challenges for newly developed and existing turbulence models in computational fluid dynamics (CFD) simulations. The present study investigates the performance of the Dynamic Hybrid RANS-LES (DHRL) model with a newly proposed dynamic time filtering (DTF) technique, compared against an industry standard Reynolds-Averaged Navier-Stokes (RANS) model, Monotonically Integrated Large Eddy Simulation (MILES), and two conventional Hybrid RANS-LES (HRL) models. Model performance is evaluated based on comparison to previously documented Large Eddy Simulation (LES) results. Simulations are performed for a fully developed flow in a channel with time-periodic driving pressure gradient. Results highlight the relative merits of each model type and indicate that the use of a dynamic time filtering technique improves the accuracy of the DHRL model when compared to a static time filtering technique. A comprehensive evaluation of the results suggests that the DHRL-DTF method provides the most consistently accurate reproduction of the time-dependent mean flow characteristics for all models investigated.
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Vijiapurapu, Sowjanya, and Jie Cui. "Numerical Simulation of Turbulent Flows in Ribbed Pipes." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-80565.

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The Reynolds averaged Navier-Stokes (RANS) equations were solved along with three turbulence models, namely κ-ε, κ-ω, and Reynolds stress models (RSM), to study the fully developed turbulent flows in circular pipes roughened by repeated square ribs. The spacing between the ribs was varied to form three representative types of surface roughness; d–type, intermediate, and k–type. Solutions of these flows at two Reynolds numbers were obtained using the commercial computational fluid dynamics (CFD) software Fluent. The numerical results were validated against experimental measurements and other numerical data published in literature. Extensive investigation of effects of rib spacing and Reynolds number on the pressure and friction resistance, flow and turbulence distribution was presented. The performance of three turbulence models was also compared and discussed.
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Davis, Dustin W., Junghwa Nolan, Justin T. Brumberg, Ertan Yilmaz, Balachandar Varatharajan, Jeffrey S. Goldmeer, and Benjamin P. Lacy. "The Effect of Fuel Density on Mixing Profiles in a DACRS Type Premixer: Experiments and Simulation." In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27878.

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A combined experimental and computational study was conducted to investigate the effect of fuel density variations on mixing from a double annular counter-rotating swirl (DACRS) nozzle operated at atmospheric pressure under non-reacting conditions using either helium (He) or a mixture of He and CO2 as fuel simulants. A small probe traversed through the flow collecting gas samples that were sent to gas analyzers measuring the concentration profiles. The resulting measurements are then used to validate the computational fluid dynamics (CFD) model. A commercial CFD code (CFX 10) with a Reynolds averaged Navier-Stokes (RANS) formulation was used to simulate the experiment. Multiple turbulence closures, such as standard and realizable k-ε and SSG Reynolds stress model were evaluated. Additionally, several geometrical considerations, such as modeling a 72° sector versus a full 360°, were tested. While at high fuel-to-air momentum flux ratios (J) the fuel simulant concentration profiles were outward-peaked, and at low J the profiles were center-peaked. An analysis of the experimental results clearly indicate the momentum flux ratio is the most influential parameter controlling mixing in a DACRS nozzle. The simulations produced quantitative agreement with the experimental measurements using the realizable k-ε turbulence closure and only modeling a 72° sector of the nozzle. The complexity of the studied problem required a considerable refinement of the grid to produce an accurate and grid independent solution. The validated model may now be used to explore the design space for optimization of a nozzle for utilization in a syngas application.
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Lin, Fan, Fangfei Ning, and Huoxing Liu. "Aerodynamics of Compressor Casing Treatment: Part I—Experiment and Time-Accurate Numerical Simulation." In ASME Turbo Expo 2008: Power for Land, Sea, and Air. ASMEDC, 2008. http://dx.doi.org/10.1115/gt2008-51541.

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This paper presents both experimental and unsteady RANS investigations of a slot-type casing treatment at a transonic axial flow compressor rotor. Experimental results show that at 60% and 98% of rotor design wheel speeds, approximately 100% and 200% extra extensions of the rotor operation ranges are achieved, respectively. On the other hand, there are about 3.6% and 2.0% drops of efficiencies at 60% and 98% speeds respectively if comparisons are made at the same peak-efficiency mass flow rates of the solid casing case. If comparing the respective peak efficiencies for the solid casing case with those for the treated casing case, there are still about 3.4% and 0.7% drops at 60% and 98% speeds, respectively. As for the unsteady RANS study, an in-house unsteady RANS code has been used to study the casing treatment flow at several operating points, i.e., the peak efficiency and the near stall with regard to the solid casing case at 60% speed and 98% speed, respectively. It is shown that the interactions between the blade passage flow and the casing treatment flow exhibit different manner at two rotating speeds. The flow condition in which the rotor operates, i.e., either the subsonic condition at the 60% speed or the transonic condition with passage shock presented at the 98% speed, is one of the determinate factors that are responsible for the manner the casing treatment works. The loss production due to casing treatment is also particularly discussed.
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Rafiee, Ashkan, Bjoern Elsaesser, and Frederic Dias. "Numerical Simulation of Wave Interaction With an Oscillating Wave Surge Converter." In ASME 2013 32nd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/omae2013-10195.

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This paper deals with numerical studies of wave interaction with an Oscillating Wave Surge Converters (OWSC) using a Godunov–type SPH method. The use of a Riemann solver in calculating the density field results in a smoother SPH pressure field. Hence, a more accurate estimation of loads on the OWSC is achieved. Furthermore, the Lagrangian form of the RANS k–ε model is included in the SPH equations to better capture the turbulent features of the flow. SPH simulations were performed in both two–dimensions (2D) and three–dimensions (3D) and results for the flow pattern and loads are compared with experimental data.
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10

Insinna, Massimiliano, Simone Salvadori, and Francesco Martelli. "Simulation of Combustor/NGV Interaction Using Coupled RANS Solvers: Validation and Application to a Realistic Test Case." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-25433.

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Numerical techniques are commonly used during both design and analysis processes, mainly considering single components. Technological progress asks for advanced approaches that include real-machine conditions and analyze components interaction, especially considering the combustor/turbine coupling. Modern combustors operate with strong swirl motions in order to obtain an adequate flame stabilization, generating a very complex flow field characterized by high turbulence level. These aspects affect performance of downstream components which are subjected to very aggressive inlet flow conditions: non-uniform total temperature, non-uniform total pressure, swirl and high turbulence intensity. For these reasons coupled analysis of combustor and turbine is necessary to accurately predict aero-thermal aspects that influence performance and reliability of these two components. From a numerical point of view the simulation of a single domain characterized by a reactive flow with very different Mach number regimes (from low-Mach flow in combustion chamber to transonic flow in turbine) is problematic due to the different numerical requirements needed, especially concerning stability and accuracy. These problems could be overcome using coupled methods to simultaneously simulate combustor and turbine in separated domains which are managed by different solvers that communicate with each other. A coupling method for the study of combustor/turbine interaction using the RANS methodology is proposed. In the first part of the paper the method is described and validated. The second part is dedicated to the application of the proposed coupling methodology to a realistic test case consisting of a model annular combustor and the Nozzle Guide Vane (NGV) of the MT1 high-pressure turbine stage. A commercial solver and an in-house code are respectively used for the simulation of combustor and NGV. Results are presented and analyzed highlighting the importance of such type of simulations in understanding aero-thermal phenomena that characterize combustor/vane interaction.
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