Relevant bibliographies by topics / Simulation URANS

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  2. Dissertations / Theses
  3. Book chapters
  4. Conference papers
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Academic literature on the topic 'Simulation URANS'

Author: Grafiati
Published: 4 June 2021
Last updated: 10 February 2022

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Journal articles on the topic "Simulation URANS"

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Ehrle, Maximilian, Andreas Waldmann, Thorsten Lutz, and Ewald Krämer. "Simulation of transonic buffet with an automated zonal DES approach." CEAS Aeronautical Journal 11, no. 4 (September 1, 2020): 1025–36. http://dx.doi.org/10.1007/s13272-020-00466-7.

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Abstract A study of transonic buffet on the NASA Common Research Model at flight Reynolds numbers is presented. The ability of two different hybrid RANS/LES models as well as the URANS approach for resolving three-dimensional buffet motion was evaluated by means of spectral analysis. Automated Zonal DES and URANS simulations show similar results in terms of buffet frequency and spanwise propagation of buffet cells, whereas the Delayed Detached Eddy Simulation results indicate a strong interaction between flow separation and shock motion. The extracted characteristic frequencies which are associated with transonic buffet are located in a range of Sr = 0.2–0.65 for URANS and AZDES and are therefore in accordance with findings from related recent research. Furthermore, the simulation time series were investigated and a structure of spanwise moving buffet cells with varying convection speed and wavelength could be observed.
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Escarti-Guillem, Mara S., Sergio Hoyas, and Luis M. García-Raffi. "Rocket plume URANS simulation using OpenFOAM." Results in Engineering 4 (December 2019): 100056. http://dx.doi.org/10.1016/j.rineng.2019.100056.

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Kim, Changhee, and Changmin Son. "Comparative Study on Steady and Unsteady Flow in a Centrifugal Compressor Stage." International Journal of Aerospace Engineering 2019 (June 9, 2019): 1–12. http://dx.doi.org/10.1155/2019/9457249.

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Steady Reynolds-averaged Navier-Stokes (RANS) simulation with the mixing-plane approach is the most common procedure to obtain the performance of a centrifugal compressor in an industrial development process. However, the accurate prediction of complicated flow fields in centrifugal compressors is the most significant challenge. Some phenomena such as the impeller-diffuser flow interaction generates the unsteadiness which can affect the steady assumption. The goal of this study is to investigate the differences between the RANS and URANS simulation results in a centrifugal compressor stage. Simulations are performed at three operating points: near surge (NS), design point (DP), and near choke (NC). The results show that the RANS simulation can predict the overall performance with reasonable accuracy. However, the differences between the RANS and URANS simulation are quite significant especially in the region that the flows are highly unsteady or nearly separated. The RANS simulation is still not very accurate to predict the time-dependent quantities of the flow structure. It shows that the URANS calculations are necessary to predict the detailed flow structures and performance. The phenomena and mechanisms of the complex and highly unsteady flow in the centrifugal compressor with a vaned diffuser are presented and analyzed in detail.
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Chang, Kyoungsik, George Constantinescu, and Seung-O. Park. "Assessment of Predictive Capabilities of Detached Eddy Simulation to Simulate Flow and Mass Transport Past Open Cavities." Journal of Fluids Engineering 129, no. 11 (June 5, 2007): 1372–83. http://dx.doi.org/10.1115/1.2786529.

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The three-dimensional (3D) incompressible flow past an open cavity in a channel is predicted using the Spalart–Almaras (SA) and the shear-stress-transport model (SST) based versions of detached eddy simulation (DES). The flow upstream of the cavity is fully turbulent. In the baseline case the length to depth (L∕D) ratio of the cavity is 2 and the Reynolds number ReD=3360. Unsteady RANS (URANS) is performed to better estimate the performance of DES using the same code and meshes employed in DES. The capabilities of DES and URANS to predict the mean flow, velocity spectra, Reynolds stresses, and the temporal decay of the mass of a passive contaminant introduced instantaneously inside the cavity are assessed based on comparisons with results from a well resolved large eddy simulation (LES) simulation of the same flow conducted on a very fine mesh and with experimental data. It is found that the SA-DES simulation with turbulent fluctuations at the inlet gives the best overall predictions for the flow statistics and mass exchange coefficient characterizing the decay of scalar mass inside the cavity. The presence of inflow fluctuations in DES is found to break the large coherence of the vortices shed in the separated shear layer that are present in the simulations with steady inflow conditions and to generate a wider range of 3D eddies inside the cavity, similar to LES. The predictions of the mean velocity field from URANS and DES are similar. However, URANS predictions show poorer agreement with LES and experiment compared to DES for the turbulence quantities. Additionally, simulations with a higher Reynolds number (ReD=33,600) and with a larger length to depth ratio (L∕D=4) are conducted to study the changes in the flow and shear-layer characteristics, and their influence on the ejection of the passive contaminant from the cavity.
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Nakayama, A., and K. Miyashita. "URANS simulation of flow over smooth topography." International Journal of Numerical Methods for Heat & Fluid Flow 11, no. 8 (December 2001): 723–45. http://dx.doi.org/10.1108/09615530110409394.

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Merzari, E., H. Ninokata, R. Mereu, E. Colombo, and F. Inzoli. "URANS Simulation of Confined Parallel Jet Mixing." Nuclear Technology 175, no. 3 (September 2011): 538–52. http://dx.doi.org/10.13182/nt10-148.

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Yang, Guangjun, Xiaoxiao Li, Li Ding, Fahua Zhu, Zhigang Wang, Sheng Wang, Zhen Xu, Jingxin Xu, Pengxiang Qiu, and Zhaobing Guo. "CFD Simulation of Pollutant Emission in a Natural Draft Dry Cooling Tower with Flue Gas Injection: Comparison between LES and RANS." Energies 12, no. 19 (September 24, 2019): 3630. http://dx.doi.org/10.3390/en12193630.

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Accurate prediction of pollutant dispersion is vital to the energy industry. This study investigated the Computational Fluid Dynamics (CFD) simulation of pollutant emission in a natural draft dry cooling tower (NDDCT) with flue gas injection. In order to predict the diffusion and distribution characteristics of the pollutant more accurately, Large Eddy Simulation (LES) was applied to predict the flow field and pollutant concentration field and compared with Reynolds Average Navier-Stokes (RANS) and Unsteady Reynolds Average Navier-Stokes (URANS). The relationship between pollutant concentration pulsation and velocity pulsation is emphatically analyzed. The results show that the flow field and concentration field simulated by RANS and URANS are very close, and the maximum value of LES is about 43 times that of RANS and URANS for the prediction of pollutant concentration in the inner shell of cooling tower. Pollutant concentration is closely related to local flow field velocity. RANS and URANS differ greatly from LES in flow field prediction, especially at the outlet and downwind of cooling tower. Compared with URANS, LES can simulate flow field pulsation with a smaller scale and higher frequency.
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Salunkhe, Sanchit, Oumnia El Fajri, Shanti Bhushan, David Thompson, Daphne O’Doherty, Tim O’Doherty, and Allan Mason-Jones. "Validation of Tidal Stream Turbine Wake Predictions and Analysis of Wake Recovery Mechanism." Journal of Marine Science and Engineering 7, no. 10 (October 11, 2019): 362. http://dx.doi.org/10.3390/jmse7100362.

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This paper documents the predictive capability of rotating blade-resolved unsteady Reynolds averaged Navier-Stokes (URANS) and Improved Delayed Detached Eddy Simulation (IDDES) computations for tidal stream turbine performance and intermediate wake characteristics. Ansys/Fluent and OpenFOAM simulations are performed using mixed-cell, unstructured grids consisting of up to 11 million cells. The thrust, power and intermediate wake predictions compare reasonably well within 10% of the experimental data. For the wake predictions, OpenFOAM performs better than Ansys/Fluent, and IDDES better than URANS when the resolved turbulence is triggered. The primary limitation of the simulations is under prediction of the wake diffusion towards the turbine axis, which in return is related to the prediction of turbulence in the tip-vortex shear layer. The shear-layer involves anisotropic turbulent structures; thus, hybrid RANS/LES models, such as IDDES, are preferred over URANS. Unfortunately, IDDES fails to accurately predict the resolved turbulence in the near-wake region due to the modeled stress depletion issue.
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Martineau Rousseau, Philippe, Azzeddine Soulaïmani, and Michel Sabourin. "Efficiency Assessment for Rehabilitated Francis Turbines Using URANS Simulations." Water 13, no. 14 (July 7, 2021): 1883. http://dx.doi.org/10.3390/w13141883.

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Due to the large number of aging hydraulic turbines in North America, rehabilitation is a growing market as these turbines have low efficiency compared to modern ones. Computational Fluid Dynamics identifies components with poor hydraulic performance. The models often used in industry are based on individually analyzing the sub-components of a turbine instead of full turbine simulations due to computational and time limitations. An industrial case has shown that such analyses may lead to underestimating the efficiency increases by modifying the stay vane. The unsteady full turbine simulation proposes to simulate all components simultaneously to assess this efficiency augmentation due to stay vane rehabilitation. The developed simulation methodology is used to evaluate the efficiency increase and the flow of two rehabilitated turbines with stay vane modifications. Comparison with model tests shows the accuracy of the simulations. However, the methodology used shows imprecision in predicting the efficiency increase compared to model tests. Further works should consider the use of more complex flow modeling methods to measure the efficiency increase by the stay vane modifications.
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Kratzsch, Christoph, Amjad Asad, and Rüdiger Schwarze. "CFD of the MHD Mold Flow by Means of Hybrid LES/RANS Turbulence Modeling." Journal for Manufacturing Science and Production 15, no. 1 (March 31, 2015): 49–57. http://dx.doi.org/10.1515/jmsp-2014-0046.

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AbstractIn the last decades, electromagnetic braking (EMBr) systems become a powerful tool to dampen possible jet oscillations in the continuous casting mold. Further studies showed that if a EMBr is not positioned correctly, it can induce flow oscillations. Hence, the design of these braking systems can be promoted by adequate CFD simulations. In most cases, unsteady RANS simulations (URANS) are sufficient to resolve low-frequency, large-scale oscillations of these MHD flows. Alternatively, Large Eddy Simulations (LES) may also resolve important details of the turbulence. However, since they require much finer computational grids, the computational costs are much higher. A bridge between both approaches are hybrid methods like the Scale Adaptive Simulation (SAS). In this study, we compare the performance of SAS with URANS and LES. Results are validated in detail by comparison with data from a Ruler-EMBr model experiment.
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Dissertations / Theses on the topic "Simulation URANS"

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Guillaud, Nathanaël. "Simulation et optimisation de forme d'hydroliennes à flux transverse." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAI061.

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Dans le cadre de la production d'électricité par énergie renouvelable, cette thèse a pour objectif de contribuer à l'amélioration des performances hydrodynamiques des hydroliennes à flux transverse conçues par HydroQuest. Pour y parvenir, deux axes d'étude principaux sont proposés. Le premier consiste à améliorer la compréhension de la performance de l'hydrolienne et de l'écoulement en son sein par voie numérique. L'influence du paramètre d'avance ainsi que celle de la solidité de l'hydrolienne sont étudiées. Les écoulements mis en jeux étant complexes, une méthode de type Simulation des Granges Échelles 3D est utilisée afin de les restituer au mieux. Le phénomène de décrochage dynamique, qui apparaît pour certains régimes de fonctionnement de l'hydrolienne, fait l'objet d'une étude à part entière sur un cas de profil oscillant.Le second axe se concentre sur les carénages de l’hydrolienne qui font l'objet d'une procédure d'optimisation numérique. Afin de pouvoir réaliser les nombreuses simulations requises en un temps réaliste, des méthodes de type Unsteady Reynolds-Averaged Navier-Stokes 2D moins coûteuses et fournissant une précision suffisante pour ce type d'étude sont utilisées
Within the renewable electricity production framework, this study aims to contribute to the efficiency improvement of the Vertical Axis Hydrokinetic Turbines designed by HydroQuest. To achieve this objective, two approaches are used. The first consists in the improvement of the comprehension of the turbine efficiency such as the flow through the turbine by numerical means. The influence of the tip speed ratio such as the turbine soldity are investigated. The flow through the turbine is complex. A 3D Large Eddy Simulation type is thus used. The dynamic stall phenomenon which could occur in Vertical Axis Hydrokinetic Turbines is also studied in a oscillating blade configuration.The second approach consists in the numerical optimization of the turbine channeling device. To perform the high number of simulations required, a 2D Unsteady Reynolds-Averaged Navier-Stokes simulation type is used
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Takai, Tomohiro. "Simulation based design for high speed sea lift with waterjets by high fidelity urans approach." Thesis, University of Iowa, 2010. https://ir.uiowa.edu/etd/748.

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Carpy, Sabrina. "Contribution à la modélisation instationnaire de la turbulence : modélisations urans et hybride rans/les." Poitiers, 2006. http://www.theses.fr/2006POIT2342.

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Cette thèse concerne la modélisation instationnaire de la turbulence. La présence de structures à grande échelle dans des écoulements statistiquement stationnaires invalide certaines hypothèses. L’introduction du terme pour les équations URANS ne suffit pas, une nouvelle décomposition et un opérateur associé sont nécessaires. L’applicabilité des méthodes de fermeture usuelles doit alors être vérifiée. Par exemple, la périodicité du jet synthétique entraîne un non-équilibre créant un non-alignement permanent des tensions de déformation et d’anisotropie que le modèle RSM reproduit mais pas le modèle k-ε. La modélisation hybride RANS/LES non-zonale, dérivée d’une proposition initiale de Schiestel, repose donc sur des équations de transport pour les tensions de Reynolds (ij)SGS, et pour la dissipation, où l’opérateur de décomposition joue le rôle d’un filtre dont la fréquence de coupure peut être maîtrisée. La qualité des résultats obtenus sur une couche de mélange temporelle atteste de la capacité de ce modèle à capter les grandes structures de l’écoulement
The aim of this work is to account for the unsteadiness effects on the turbulence in single point closure. The existence of large scale structures in statistically steady flows leads to reconsider some hypothesis. Much more than adding the time derivatives , the URANS equations needs to consider a new decomposition and an assiociated operator. Therefore, the applicability of usual closure methods has to be examined. For exemple, the periodicity of a synthetic jet leads to a non-equilibrium, which induces a permanent misalignment of anisotropy tensor and strain tensors. RSM are able to reproduce this misalignment, whereas k-ε. Model can't. A seamless hybrid RANS/LES method, based on the version of Schiestel's model, relies on transport equations for the subgrid stress (ij)SGS and dissipation. The decomposition operator is then assimilated as a filter with an adapatative cutoff frequency. The predictions obtained on a temporal mixing layer shows the ability of this model to capture the very large structure of the flow
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Schmidt, Stephan [Verfasser]. "Entwicklung einer hybriden LES-URANS-Methode für die Simulation interner und externer turbulenter Strömungen / Stephan Schmidt." Hamburg : Helmut-Schmidt-Universität, Bibliothek, 2016. http://d-nb.info/1120531772/34.

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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.

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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 this work was to apply LES to a variety of natural ventilation strategies and to compile guidelines for practitioners on its performance, including the trade-off between accuracy and cost.
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Benyoucef, Farid. "Amélioration de la prévision des écoulements turbulents par une approche URANS avancée." Thesis, Toulouse, ISAE, 2013. http://www.theses.fr/2013ESAE0014/document.

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Ces travaux de recherche ont pour but d’évaluer la méthode dite de la "Simulation auxEchelles Adaptées" (SAS pour Scale-Adaptive Simulation). Cette approche coïncide avec uneapproche RANS classique dans les zones pariétales attachées et adapte le niveau de viscositéturbulente dans les zones décollées pour y permettre une résolution partielle des structures turbulentes.Dans une première partie, une analyse théorique du modèle SAS original a été menéeet a permis de développer une correction visant à favoriser l’adaptation du niveau de viscositéturbulente dans les zones sièges d’instabilités de type Kelvin-Helmholtz. Le modèle ainsi corrigéest nommé SAS-αL. Les modèles SAS et SAS-αL ont été implantés dans le code de calculNavier-Stokes elsA de l’ONERA. À l’issue de cette étape, trois cas académiques d’écoulementsturbulents instationnaires, cylindre à grand nombre de Reynolds, marche descendante et cavitétranssonique, ont été simulés grâce aux trois modèles de turbulence SST, SAS et SAS-αL. Outreune comparaison aux bases de données expérimentales disponibles, une attention particulièrea été portée à l’influence de paramètres numériques tels que des schémas numériques d’ordreélevé. Enfin, afin d’étudier la viabilité de l’approche SAS dans un contexte industriel, les troismodèles de turbulence ont été testés sur une configuration issue de l’industrie aéronautique etcorrespondant à la sortie d’air chaud d’un système de dégivrage des nacelles d’avion. La comparaisondes prévisions obtenues avec les modèles SST, SAS et SAS-αL aux données expérimentalesobtenues à l’ONERA a permis de montrer un gain de précision grâce à l’emploi de l’approcheSAS et ce pour un coût de calcul compatible avec un cycle de conception industrielle
This research work is meant to assess an upgraded URANS approach, namely the Scale-Adaptive Simulation (SAS). This method is similar to a conventional RANS approach (namelythe SSTmodel) in attached areas and is able to adapt the eddy-viscosity level in detached areas toensure the resolution, at least partially, of the turbulent structures. In a first part of this researchwork, an improvement of the SAS approach is suggestedto allowa better sensitivity of themodelto instabilities such as Kelvin-Helmholtz ones. This "improved" model is referred to as SAS-αLmodel. Both SAS and SAS-αL models were implemented in the ONERA Navier-Stokes solverelsA and both of themaswell as the SSTmodelwere tested on academic test cases : a cylinder in acrossflowat a high Reynolds number, a backward-facing step flowcorresponding to theDriver&Seegmiller experiment and the transonic flow over the M219 cavity experimentally investigatedby de Henshaw. The influence of the numerical parameters was deeply investigated and particularattention was paid to the high-order space-discretization schemes effects. The reliabilityof the SAS approach in an industrial framework was assessed on an aeronautic configurationnamely a nacelle de-icing device. Comparisons between the threemodels (SST, SAS and SAS-αL)and an experimental database available at ONERA - The French Aerospace Lab have shown thebetter accuracy of the SAS approach as well as the high potential of the SAS-αL model
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Decaix, Jean. "Modélisation et simulation de la turbulence compressible en milieu diphasique : application aux écoulements cavitants instationnaires." Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00814309.

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La simulation des écoulements cavitants est confrontée à des difficultés de modélisation et de résolution numérique provenant des caractéristiques particulières de ces écoulements : changement de phase, gradient de masse volumique important, variation du nombre de Mach, turbulence diphasique, instationnarités. Dans cette thèse, nous nous sommes appliqués à dériver proprement le modèle de mélange homogène 1-fluide couplé à une modélisation RANS de la turbulence. A partir des termes contenus dans ces équations et de la nature des écoulements cavitants étudiés, plusieurs modèles de turbulence basés sur la notion de viscosité turbulente ont été testés : modèles faiblement non-linéaires (corrections SST et de réalisabilité), ajout des termes de turbulence compressible, application de la correction de Reboud, modèles hybrides RANS/LES (DES, SAS). Ces modèles ont été incorporés dans un code compressible qui fait appel à une résolution implicite en pas de temps dual des équations de conservation avec une technique de pré-conditionnement bas-Mach pour traiter les zones incompressibles. Les simulations 2D et 3D ont porté sur deux géométries de type Venturi caractérisées par la présence d'une poche de cavitation instationnaire due à l'existence d'un jet rentrant liquide/vapeur le long de la paroi. Elles montrent que l'ensemble des modèles sont capables de capturer le jet rentrant. En revanche, la dynamique de la poche varie entre les modèles et le manque de données expérimentales ne permet pas de discriminer les modèles entre eux. Il apparaît à la vue des résultats que les approches avec la correction de Reboud ou les modèles SAS améliorent la simulation des écoulements.
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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 Laboratoire des Ecoulements Géophysiques et Industriels (LEGI),qui visent à améliorer la compréhension et la modélisation d'écoulements cavitants. Les simulations s'appuient sur un code compressible associé à une technique de pré-contionnement bas-Mach qui permet de traiter les zones incompressibles. Les écoulements diphasiques sont reproduits à l'aide d'un modèle de mélange homogène 1-fluide avec discrétisation implicite en pas de temps dual. Enfin la résolution adopte l'approche moyennée RANS qui couple le système des équations de conservation avec des modèles de turbulence du premier ordre basés sur la notion de viscosité turbulente.Dans les zones diphasiques, le calcul des variables thermodynamiques nécessite l'introduction d'équations d'état. La pression au sein du mélange est ainsi reliée aux grandeurs conservatives soit à partir d'une équation d'état de mélange des gaz raides, soit par une relation sinusoïdale incorporant la fraction volumique de vapeur (le taux de vide). La valeur ajoutée de ces travaux de thèse repose sur l'introduction d'une équation de transport pour le calcul du taux de vide. Celle-ci incorpore un terme source dont le transfert de masse entre les phases est fermé grâce à une hypothèse de proportionnalité à la divergence du champ de vitesse. Outre l'amélioration des phénomènes de convection, de dilatation et de collapse, cette équation supplémentaire permet de relaxer l'équilibre thermodynamique local et d'introduire un état métastable pour la phase vapeur.Les simulations 2D et 3D sont réalisées sur des géométries de type Venturi caractérisées par le développement de poches de cavitation partielle instables. L'objectif consiste à reproduire les instationnarités inhérentes à chaque profil telles que la formation d'un jet rentrant liquide à proximité de la paroi ou la production de nuages de vapeur convectés par l'écoulement principal.Les résultats numériques mettent en avant une variation de la fréquence des instationnarités en fonction du calcul de la vitesse du son en zone de mélange. D'autre part, la prise en compte de déséquilibre de la phase vapeur amplifie les phénomènes de propagation d'ondes de pression générées par le collapse des structures cavitantes et participe à la déstabilisation de la poche. Enfin, l'influence de l'équation de transport de taux de vide est analysée en confrontant les résultats des simulations à ceux obtenus ultérieurement à partir d'un modèle à seulement trois équations de conservation
The 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
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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 qui varie cycliquement. Elle trouve son application dans l’étude et le développement des énergies marines renouvelables, et plus particulièrement des machine d’extraction d’énergie cinétique de courants de marée ou fluvial à axe transverse. L’objectif est de construire des outils de simulation permettant une étude approfondie des possibilités des systèmes à axe transverse avec variation cyclique active de pas. Pour répondre à cela deux stratégies de modélisation ont été suivies. D’une part l’adaptation du pas variable à une méthode énergétique couplée à différents modèles de prédiction des efforts instationnaires sur un profil; et d’autre part une simulation URANS avec maillage tournant/déformant pour prendre en compte cette variation de pas. La variation d’angle de calage a permis d’obtenir me augmentation de performance maximal de 52%. L’essai des différents modèles fluides disponibles a mis en évidence l’efficacité du modèle turbulent. Le modèle de transition, pourtant prometteur et semblant plus adapté aux cas d’application considérés, s’est révélé peu performant, mais aucune investigation supplémentaire n’a été effectuée. La comparaison avec l’expérience dans le cas turbulent avec modèle de turbulence kw - SST s’est révélée encourageante, notamment pour les rapports de vitesse périphériques opérationnels, autour de ʎ = 5. Pour les ʎ plus faibles les résultats sont en moyenne similaires mais le modèle peine à reproduire les variations aux fréquences naturelles du décrochage, dues aux lâchers tourbillonnaires. La continuité de cette étude réside d’une part dans l’étude d’autres lois de calage, et d’autre part dans l’application à un système concret pour pouvoir aboutir à des systèmes transverses plus efficace
This 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
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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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Book chapters on the topic "Simulation URANS"

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Mühlbauer, Bernd, Berthold Noll, Roland Ewert, Oliver Kornow, and Manfred Aigner. "Numerical RANS/URANS simulation of combustion noise." In Combustion Noise, 1–31. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-02038-4_1.

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Schmidt, S., and M. Breuer. "Hybrid LES–URANS Methodology for Wall–Bounded Flows." In Direct and Large-Eddy Simulation IX, 197–203. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-14448-1_25.

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Fedorova, N. N., I. A. Fedorchenko, and Y. V. Semenova. "Flow simulation of inlet components using URANS approach." In Shock Waves, 1261–66. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-540-85181-3_75.

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Schmidt, S., and M. Breuer. "Application and Extension of a Synthetic Turbulence Inflow Generator Within a Hybrid LES–URANS Methodology." In Direct and Large-Eddy Simulation X, 63–69. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-63212-4_7.

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Zhong, Bowen, Satish K. Yadav, and Dimitris Drikakis. "Turbulent Flow Simulations Around an Airfoil At High Incidences Using URANS, DES and ILES Approaches." In Direct and Large-Eddy Simulation VII, 519–26. Dordrecht: Springer Netherlands, 2010. http://dx.doi.org/10.1007/978-90-481-3652-0_77.

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van der Burg, J. W., and M. Luehmann. "Simulation of Maximum Lift Using URANS for a High-Lift Transport Configuration." In Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 75–88. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-38877-4_6.

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Han, X., S. Krajnović, C. H. Bruneau, and I. Mortazavi. "Comparison of URANS, PANS, LES and DNS of Flows Around Simplified Ground Vehicles with Passive Flow Manipulation." In Direct and Large-Eddy Simulation IX, 57–63. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-14448-1_8.

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Doerffer, Piotr, Charles Hirsch, Jean-Paul Dussauge, Holger Babinsky, and George N. Barakos. "WP-4 RANS/URANS Simulations (Charles Hirsch)." In Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 327–38. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-03004-8_13.

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Gmelin, Christoph, Mathias Steger, Erik Wassen, Frank Thiele, André Huppertz, and Marius Swoboda. "URANS Simulations of Active Flow Control on Highly Loaded Turbomachinery Blades." In Active Flow Control II, 203–19. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-11735-0_14.

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Fraňa, Karel, and Jörg Stiller. "A Hybrid URANS/LES Approach Used for Simulations of Turbulent Flows." In Springer Proceedings in Physics, 139–42. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-02225-8_33.

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Conference papers on the topic "Simulation URANS"

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Etemad, Sassan, and Peter Gullberg. "Validation of URANS Simulation of Truck Cooling Fan Performance." In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-38383.

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The performance of an axial heavy duty truck cooling fan was investigated by measurements in a test rig and by CFD simulations. In order to account for the unsteadiness of the flow, URANS simulations were employed. Good agreement was achieved between the simulation and test data, in particular in the axial regime, despite the constant density assumption. To improve the simulation accuracy in the radial and transitional regime it is most likely insufficient to assume constant density. New simulations with ideal gas assumptions for these regimes are believed to give better agreement with the test data. The simulations show that URANS CFD can produce results very close to the ones obtained in the test facilities and thereby can be used for the industrial applications when flow unsteadiness has to be taken into account. The fact that it requires long computational time and is CPU-demanding can no longer be regarded as a major preventing factor for its application in the industry. In addition, it provides valuable information about the details of the flow which can contribute to the optimization of the geometry for improved efficiency and higher performance.
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Kannan, K. V., and G. J. Page. "Automated Multi-Code URANS Simulation of Compressor-Combustor Components." In ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-56904.

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Currently in an aircraft gas turbine engine, the turbomachinery and combustor components are designed in relative isolation and the effect of the upstream and downstream components on each other’s flow are not fully captured in the design process. The objective of this work is to carry out a multi-code integrated unsteady simulation of Compressor-Combustor components with each zone simulated using its own specialised CFD flow solver. The multi-code URANS technique is simple, based on files and involves the generation of new 2D boundary conditions for the required flow field at each time step. A driver based on a Python script automates the entire process. This paper shows the method first validated in a simple vortex shedding 2D case and then extended to a cold flow URANS simulation matching an isothermal compressor/combustor rig experiment. An external coupler code is invoked that produces unsteady, spatially varying, inlet conditions for the downstream components. The simulation results are encouraging as the mass, momentum and energy losses across the interface are less than 1%. The multi-code unsteady simulation produces wake profiles closer to the experiment than the coupled steady RANS simulation. The present study shows a reasonable agreement with the experimental PIV and hot-wire data thus demonstrating the potential of the multi-code integrated simulation technique.
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Grinstein, Fernando, Rick Rauenzahn, Juan Saenz, and Marianne Francois. "Coarse Grained Simulation of Shock-Driven Turbulent Mixing." In ASME 2017 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/fedsm2017-69057.

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We focus on the simulation of shock-driven material mixing powered by flow instabilities dependent on initial conditions (IC) at the material interfaces. Beyond complex multi-scale resolution issues of shocks and variable density turbulence, we must address the equally difficult problem of predicting flow transition promoted by energy deposited at the interfacial layers during the shock-interface interactions. Transition involves IC-dependent, large-scale coherent-structure dynamics capturable by a large eddy simulation (LES) strategy, but not by unsteady Reynolds-Averaged Navier-Stokes (URANS) approaches based on equilibrium developed turbulence assumptions and single-point-closure modeling. On the engineering end of computations, reduced-dimensionality (1D/2D) versions of such URANS tend to be preferred for faster turnaround in full-scale configurations. With suitable initialization around each transition, URANS can be used to simulate the subsequent near-equilibrium weakly turbulent flow. We demonstrate 3D state-of-the-art URANS performance around one such (reshock) transition — in the context of a sequential LES/URANS strategy.
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Zhang, Zhiguo, Lixiang Guo, Shuang Wang, Ye Yuan, and Can Chen. "URANS Simulation of ONR Tumblehome Parametric Rolling in Regular Head Waves." In ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/omae2019-96425.

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Abstract In this paper, an in-house CFD code HUST-Ship is used for the numerical simulation of parametric rolling phenomena of ONR Tumblehome in regular head wave. Preliminary resistance and roll decay simulations at Fr = 0.2 were carried out and compared with existed INSEAN experimental data. Following, three DOFs’ ship motions in regular head wave with an initial roll angle of 30 degrees was calculated to examine the possibility of occurrence of parametric rolling. Finally, a simulation without initial roll disturbance was performed to investigate its influence to the steady roll amplitude. By conducting fast Fourier transform of the time history of motions, forces and moments, the characteristics are analyzed and co-related with wave frequency. Results can be concluded that the in-house code has the ability to perform the parametric rolling simulation, and that the final steady roll amplitude is not affected by the initial disturbance. In addition, heave and pitch motions are dominantly affected by wave characteristic, roll frequency is about half that of wave, and that forces and moments in x direction exhibit high-order non-linearity.
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Tide, P. S., and V. Babu. "Aerodynamic and Acoustic Predictions from Chevron Nozzles Using URANS Simulation." In 47th AIAA Aerospace Sciences Meeting including The New Horizons Forum and Aerospace Exposition. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2009. http://dx.doi.org/10.2514/6.2009-14.

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Sadiki, Amsini, and Johannes Janicka. "UNSTEADY METHODS (URANS AND LES) FOR SIMULATION OF COMBUSTION SYSTEMS." In CHT-04 - Advances in Computational Heat Transfer III. Proceedings of the Third International Symposium. Connecticut: Begellhouse, 2004. http://dx.doi.org/10.1615/ichmt.2004.cht-04.30.

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Yu, Feiyan, and Savas Yavuzkurt. "Simulation of Film Cooling Heat Transfer and Simulation Improvement With a Modified DES Turbulence Model." In ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-86887.

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Modeling the heat transfer characteristics of the highly turbulent flow in gas turbine film cooling is important for better engineering solutions to the film cooling system design. URANS, LES, DES and modified DES models capability in simulating film cooling with a density ratio of 2.0 and blowing ratio of 1.0 are studied in this work. Detailed comparisons of simulation results with experimental data regarding the near-field and far-fields are made. For near field predictions, DES gives decent prediction with a 21.4 % deviation of centerline effectiveness, while LES and URANS have deviation of 33.6% and 51.2% compared to the experimental data. Despite good predictions for near field, DES under predicts the spanwise spreading of counter rotating vortex pair and temperature field, therefore it over predicts the centerline effectiveness in the far field. To compensate for this shortcoming of DES, the eddy viscosity in the spanwise direction is increased to enhance spanwise-diffusion of the cooling jets. The modified DES prediction of overall centerline effectiveness deviates 12.4% from experimental data, while LES, unmodified DES and URANS predictions deviate 10.8%, 31.9% and 46.9%. The modified DES model has adequate predictions of vortices evolutions which URANS modeling lacks and consumes significant less computational time than LES. It can be said that the modified DES model results in satisfactory film cooling modeling with a moderate computational cost and time.
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Di Ilio, Giovanni, Vesselin Krastev, Federico Piscaglia, and Gino Bella. "Hybrid URANS/LES Turbulence Modeling for Spray Simulation: A Computational Study." In WCX SAE World Congress Experience. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2019. http://dx.doi.org/10.4271/2019-01-0270.

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Ito, Sasuga, Masato Furukawa, Yamada Kazutoyo, and Kaito Manabe. "Adaptive Simulation Based on URANS and Ensemble Kalman Filter for Resolving Turbulent Flow on LES." In ASME 2020 Fluids Engineering Division Summer Meeting collocated with the ASME 2020 Heat Transfer Summer Conference and the ASME 2020 18th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/fedsm2020-20344.

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Abstract Turbulence is one of the most important phenomena in fluid dynamics. In general, turbulent phenomena can be resolved more clearly with Large Eddy Simulation (LES) compared with Unsteady Reynolds Averaged Navier-Stokes (URANS), and the numerical solution shows good agreements with that based on Direct Numerical Simulation (DNS). However, more time and computational power are needed on LES than those on URANS. If possible, the ideal simulation method is that the method is able to resolve the turbulent phenomena same quality as the results based on DNS and LES with less time and less computational power same as that on URANS. This paper shows an adaptive simulation method based on URANS and Ensemble Kalman Filter (Enkf) to reproduce the flow fields based on LES. In this study, a two-dimensional turbine cascade flow has been solved with URANS and LES. The adaptive simulation method has been also applied to the cascade flow. As the results, in the flow field of URANS with the assimilated turbulence model’s parameters, the separation phenomenon and the boundary layer thickness was close to that of the time averaged LES.
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Kok, Zhen, Yuting Jin, Shuhong Chai, Shaun Denehy, and Jonathan Duffy. "URANS Prediction of Berthed Ship–Passing Ship Interactions." In ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-61738.

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In this paper, the unsteady Reynolds-Averaged Navier-Stokes computational method has been employed for investigating the hydrodynamic interactions between berthed and passing ships. Initially, simulations in model-scale were performed for validating the numerical modelling technique using available benchmark experimental test cases. A formal study of verification and validation was carried out for quantifying the numerical uncertainties. Based on the validated numerical setup, systematic computations were conducted for further investigations on the influence of varying passing ship speeds and lateral separations on the interaction forces and moments. The same conditions were repeated in full scale to quantify possible scale effects. The numerical results demonstrate that the interaction forces and moments are proportional to the square of the passing ship speed and inversely proportional to the lateral separation between the two ships, which agrees well with the findings by Remery (1974) and Kriebel (1995) respectively. In addition, when comparing model and full scale results, the overall differences are not very significant and are within the simulation uncertainty for most cases.
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Reports on the topic "Simulation URANS"

1

Fasel, Hermann F., and Richard D. Sandberg. Simulation of Supersonic Base Flows: Numerical Investigations Using DNS, LES, and URANS. Fort Belvoir, VA: Defense Technical Information Center, October 2006. http://dx.doi.org/10.21236/ada459372.

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