Littérature scientifique sur le sujet « Reconstruction et simulations de flux »
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Articles de revues sur le sujet "Reconstruction et simulations de flux"
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Matringe, Sebastien F., Ruben Juanes et Hamdi A. Tchelepi. « Tracing Streamlines on Unstructured Grids From Finite Volume Discretizations ». SPE Journal 13, no 04 (1 décembre 2008) : 423–31. http://dx.doi.org/10.2118/103295-pa.
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Summary The accuracy of streamline reservoir simulations depends strongly on the quality of the velocity field and the accuracy of the streamline tracing method. For problems described on complex grids (e.g., corner-point geometry or fully unstructured grids) with full-tensor permeabilities, advanced discretization methods, such as the family of multipoint flux approximation (MPFA) schemes, are necessary to obtain an accurate representation of the fluxes across control volume faces. These fluxes are then interpolated to define the velocity field within each control volume, which is then used to trace the streamlines. Existing methods for the interpolation of the velocity field and integration of the streamlines do not preserve the accuracy of the fluxes computed by MPFA discretizations. Here we propose a method for the reconstruction of the velocity field with high-order accuracy from the fluxes provided by MPFA discretization schemes. This reconstruction relies on a correspondence between the MPFA fluxes and the degrees of freedom of a mixed finite-element method (MFEM) based on the first-order Brezzi-Douglas-Marini space. This link between the finite-volume and finite-element methods allows the use of flux reconstruction and streamline tracing techniques developed previously by the authors for mixed finite elements. After a detailed description of our streamline tracing method, we study its accuracy and efficiency using challenging test cases. Introduction The next-generation reservoir simulators will be unstructured. Several research groups throughout the industry are now developing a new breed of reservoir simulators to replace the current industry standards. One of the main advances offered by these next generation simulators is their ability to support unstructured or, at least, strongly distorted grids populated with full-tensor permeabilities. The constant evolution of reservoir modeling techniques provides an increasingly realistic description of the geological features of petroleum reservoirs. To discretize the complex geometries of geocellular models, unstructured grids seem to be a natural choice. Their inherent flexibility permits the precise description of faults, flow barriers, trapping structures, etc. Obtaining a similar accuracy with more traditional structured grids, if at all possible, would require an overwhelming number of gridblocks. However, the added flexibility of unstructured grids comes with a cost. To accurately resolve the full-tensor permeabilities or the grid distortion, a two-point flux approximation (TPFA) approach, such as that of classical finite difference (FD) methods is not sufficient. The size of the discretization stencil needs to be increased to include more pressure points in the computation of the fluxes through control volume edges. To this end, multipoint flux approximation (MPFA) methods have been developed and applied quite successfully (Aavatsmark et al. 1996; Verma and Aziz 1997; Edwards and Rogers 1998; Aavatsmark et al. 1998b; Aavatsmark et al. 1998c; Aavatsmark et al. 1998a; Edwards 2002; Lee et al. 2002a; Lee et al. 2002b). In this paper, we interpret finite volume discretizations as MFEM for which streamline tracing methods have already been developed (Matringe et al. 2006; Matringe et al. 2007b; Juanes and Matringe In Press). This approach provides a natural way of reconstructing velocity fields from TPFA or MPFA fluxes. For finite difference or TPFA discretizations, the proposed interpretation provides mathematical justification for Pollock's method (Pollock 1988) and some of its extensions to distorted grids (Cordes and Kinzelbach 1992; Prévost et al. 2002; Hægland et al. 2007; Jimenez et al. 2007). For MPFA, our approach provides a high-order streamline tracing algorithm that takes full advantage of the flux information from the MPFA discretization.
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Zerrik, E., et H. Bourray. « Flux reconstruction : sensors and simulations ». Sensors and Actuators A : Physical 109, no 1-2 (décembre 2003) : 34–46. http://dx.doi.org/10.1016/s0924-4247(03)00358-3.
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Khazari, Adil, et Ali Boutoulout. « Flux reconstruction for hyperbolic systems : Sensors and simulations ». Evolution Equations & ; Control Theory 4, no 2 (2015) : 177–92. http://dx.doi.org/10.3934/eect.2015.4.177.
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Jessen, Kristian, Margot G. Gerritsen et Bradley T. Mallison. « High-Resolution Prediction of Enhanced Condensate Recovery Processes ». SPE Journal 13, no 02 (1 juin 2008) : 257–66. http://dx.doi.org/10.2118/99619-pa.
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Summary This paper investigates the accuracy of first- and high-order numerical methods in simulating enhanced condensate processes in 1D, 2D, and 3D. We compare the predictions of a standard single point upwind (SPU) scheme with a third-order accurate finite difference (FD) simulator based on a third-order essentially nonoscillatory (ENO) flux reconstruction with matching temporal accuracy. We include physical dispersion in the mathematical model of these multiphase, multicomponent systems. The comparisons demonstrate that SPU schemes may fail to predict the formation of the mobile liquid bank at the leading edge of the displacement unless an impractical number of gridblocks is used in the simulations. In contrast, the high-order FD simulator is demonstrated to accurately predict the liquid bank at much lower grid resolution, providing for a more efficient simulation approach. In 2D displacement calculations with gravity included, the CPU requirement of the SPU scheme was found to be more than 50 times larger than for the ENO scheme for a given level of accuracy. In 2D vertical cross-sections, the predicted component recovery is demonstrated to vary upward of 8% depending on the selected numerical scheme for a given grid resolution and dispersivity. In these settings, the SPU solutions converge to the ENO results upon significant grid refinement. In 3D displacement calculations, the magnitude of the predicted condensate bank is also found to be very different depending on the selected numerical scheme. Relative to the 2D displacement calculations, condensate banking and gravity segregation is observed to have less impact on the process performance prediction because of the permeability configuration in the 3D model used here, but it could have a high impact in different settings. We include an explicit representation of longitudinal and transverse dispersion in the porous medium to demonstrate the grid resolution required to resolve physical dispersion at a given simulation length scale, and to show that condensate banks can also form in more realistic dispersive systems. Grid-refinement studies in 1D and 2D demonstrate, again, that the ENO scheme outperforms the SPU scheme for a given Peclet (Pe) number. Converged solutions are obtained with the ENO scheme using a relatively small number of grid cells. In addition, we show the behavior of the two schemes for varying Peclet numbers on a fixed simulation grid. For this grid, the ENO scheme is shown to be sensitive to the Peclet number, signifying that physical dispersion is not overwhelmed by numerical diffusion. For the SPU scheme, however, the solutions are almost independent of the Peclet number, which indicates that numerical diffusion dominates. Introduction Significant portions of the current hydrocarbon reserves are found in gas-condensate-carrying formations. Production of hydrocarbons from these reserves is expected to increase upward of 100% by 2015 (Cambridge Energy Research Associates 2005). Primary production of these reserves will result in significant loss of the heavy ends because of liquid dropout once the reservoir pressure reaches the dew point pressure. Enhanced condensate recovery by gas cycling/injection schemes are often applied to extend the lifetime of condensate reservoirs. These processes are inherently compositional, as the component transfer between an immobile liquid phase and a mobile gas phase is the key mechanism for enhancing recovery. Numerical simulation of such processes is very challenging because the prediction of the local displacement efficiency and the global sweep can be very sensitive to numerical diffusion. Various authors have shown that numerical artifacts can alter the displacement characteristics and lead to significant underprediction of the local displacement efficiency (Stalkup et al. 1990; Lim et al. 1997; Johns et al. 2002; Jessen et al. 2004). In their numerical studies of gas injection in depleted condensate reservoirs, Høier and Whitson (2001) demonstrated that near-miscible gas injection may, in some cases, lead to the formation of a condensate bank at the leading edge of the displacement. In addition, for some injection settings, the liquid bank was shown to exceed the critical liquid saturation and hence become mobile. Their analysis was based on 1D displacement calculations. The work of Jessen and Orr (2004) demonstrated that the prediction of condensate banks that exceed the critical condensate saturation by numerical calculations requires a firm control of numerical diffusion. They used analytical solutions based on the method of characteristics (MOC) (Johns et al. 1993) as well as a high-resolution FD simulator developed by Mallison et al. (2005) to investigate the complex interplay of flow and phase behavior in enhanced condensate recovery processes in 1D. In this work, we extend this investigation of enhanced condensate recovery processes to 2D and 3D. We include gravity to study the impact of a mobile liquid bank on the overall efficiency of the enhanced condensate recovery (ECR) process. We investigate the grid resolutions needed for both numerical schemes to resolve the condensate banks, and the impact of numerical errors on the predicted recovery in the presence of gravity. We also study the importance of physical dispersion in ECR processes. In particular, we are interested in understanding the grid resolution that is required to resolve the physical dispersion terms by controlling the level of numerical diffusion. We note that physical dispersion/diffusion is required to obtain a converged solution in 2D and 3D for this type of displacement problem. In the following section, we introduce the mathematical model for multicomponent multiphase flow in porous media, including an explicit representation of dispersive terms. We then describe the implementation in our compositional simulator. Next, we discuss the condensate system investigated in this work and present simulation results for enhanced condensate recovery in 1D, 2D, and 3D. Finally, we draw conclusions from the presented material.
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Trojak, W., N. R. Vadlamani, J. Tyacke, F. D. Witherden et A. Jameson. « Artificial compressibility approaches in flux reconstruction for incompressible viscous flow simulations ». Computers & ; Fluids 247 (octobre 2022) : 105634. http://dx.doi.org/10.1016/j.compfluid.2022.105634.
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Török, T., M. G. Linton, J. E. Leake, Z. Mikić, R. Lionello, V. S. Titov et C. Downs. « Solar Eruptions Triggered by Flux Emergence below or near a Coronal Flux Rope ». Astrophysical Journal 962, no 2 (1 février 2024) : 149. http://dx.doi.org/10.3847/1538-4357/ad1826.
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Abstract Observations have shown a clear association of filament/prominence eruptions with the emergence of magnetic flux in or near filament channels. Magnetohydrodynamic (MHD) simulations have been employed to systematically study the conditions under which such eruptions occur. These simulations to date have modeled filament channels as 2D flux ropes or 3D uniformly sheared arcades. Here we present MHD simulations of flux emergence into a more realistic configuration consisting of a bipolar active region containing a line-tied 3D flux rope. We use the coronal flux-rope model of Titov et al. as the initial condition and drive our simulations by imposing boundary conditions extracted from a flux emergence simulation by Leake et al. We identify three mechanisms that determine the evolution of the system: (i) reconnection displacing footpoints of field lines overlying the coronal flux rope, (ii) changes of the ambient field due to the intrusion of new flux at the boundary, and (iii) interaction of the (axial) electric currents in the preexisting and newly emerging flux systems. The relative contributions and effects of these mechanisms depend on the properties of the preexisting and emerging flux systems. Here we focus on the location and orientation of the emerging flux relative to the coronal flux rope. Varying these parameters, we investigate under which conditions an eruption of the latter is triggered.
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Ding, Yan, Sung-Chan Kim, Richard B. Styles et Rusty L. Permenter. « SIMULATION OF LONG-TERM SHORELINE CHANGE DRIVEN BY LONGSHORE AND CROSS-SHORE SEDIMENT TRANSPORT ». Coastal Engineering Proceedings, no 36v (28 décembre 2020) : 31. http://dx.doi.org/10.9753/icce.v36v.sediment.31.
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Driven by wave and current, sediment transport alongshore and cross-shore induces shoreline changes in coasts. Estimated by breaking wave energy flux, longshore sediment transport in littoral zone has been studied for decades. Cross-shore sediment transport can be significant in a gentle-slope beach and a barred coast due to bar migration. Short-term beach profile evolution (typically for a few days or weeks) has been successfully simulated by reconstructing nonlinear wave shape in nearshore zone (e.g. Hsu et al 2006, Fernandez-Mora et al. 2015). However, it is still lack of knowledge on the relationship between cross-shore sediment transport and long-term shoreline evolution. Based on the methodology of beach profile evolution modeling, a semi-empirical closure model is developed for estimating phase-average net cross-shore sediment transport rate induced by waves, currents, and gravity. This model has been implemented into GenCade, the USACE shoreline evolution model.
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Huang, Lawrence, Rupert A. C. Croft et Hitesh Arora. « Deep forest : Neural network reconstruction of the Lyman-α forest ». Monthly Notices of the Royal Astronomical Society 506, no 4 (19 juillet 2021) : 5212–22. http://dx.doi.org/10.1093/mnras/stab2041.
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ABSTRACT We explore the use of Deep Learning to infer physical quantities from the observable transmitted flux in the Ly α forest. We train a Neural Network using redshift z = 3 outputs from cosmological hydrodynamic simulations and mock data sets constructed from them. We evaluate how well the trained network is able to reconstruct the optical depth for Ly α forest absorption from noisy and often saturated transmitted flux data. The Neural Network outperforms an alternative reconstruction method involving log inversion and spline interpolation by approximately a factor of 2 in the optical depth root mean square error. We find no significant dependence in the improvement on input data signal to noise, although the gain is greatest in high optical depth regions. The Ly α forest optical depth studied here serves as a simple, one dimensional, example but the use of Deep Learning and simulations to approach the inverse problem in cosmology could be extended to other physical quantities and higher dimensional data.
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Zunz, V., et H. Goosse. « Influence of freshwater input on the skill of decadal forecast of sea ice in the Southern Ocean ». Cryosphere 9, no 2 (17 mars 2015) : 541–56. http://dx.doi.org/10.5194/tc-9-541-2015.
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Abstract. Recent studies have investigated the potential link between the freshwater input derived from the melting of the Antarctic ice sheet and the observed recent increase in sea ice extent in the Southern Ocean. In this study, we assess the impact of an additional freshwater flux on the trend in sea ice extent and concentration in simulations with data assimilation, spanning the period 1850–2009, as well as in retrospective forecasts (hindcasts) initialised in 1980. In the simulations with data assimilation, the inclusion of an additional freshwater flux that follows an autoregressive process improves the reconstruction of the trend in ice extent and concentration between 1980 and 2009. This is linked to a better efficiency of the data assimilation procedure but can also be due to a better representation of the freshwater cycle in the Southern Ocean. The results of the hindcast simulations show that an adequate initial state, reconstructed thanks to the data assimilation procedure including an additional freshwater flux, can lead to an increase in the sea ice extent spanning several decades that is in agreement with satellite observations. In our hindcast simulations, an increase in sea ice extent is obtained even in the absence of any major change in the freshwater input over the last decades. Therefore, while the additional freshwater flux appears to play a key role in the reconstruction of the evolution of the sea ice in the simulation with data assimilation, it does not seem to be required in the hindcast simulations. The present work thus provides encouraging results for sea ice predictions in the Southern Ocean, as in our simulation the positive trend in ice extent over the last 30 years is largely determined by the state of the system in the late 1970s.
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Liu, Chunlei, et Richard P. Allan. « Unrealistic Increases in Wind Speed Explain Reduced Eastern Pacific Heat Flux in Reanalyses ». Journal of Climate 31, no 8 (20 mars 2018) : 2981–93. http://dx.doi.org/10.1175/jcli-d-17-0642.1.
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Abstract Tropical eastern Pacific sea surface temperature plays a pivotal role in mechanisms that determine global mean surface temperature variability. In this study, the surface flux contribution to recent cooling of the tropical eastern Pacific is investigated using data from three atmospheric reanalyses with full assimilation of observations, an observation-based net surface energy flux reconstruction, and 15 atmosphere-only climate model simulations. For ERA-Interim, 78% of the decrease in net surface flux (−0.65 W m−2 yr−1 over 1988–2008) is explained by the latent heat flux variability. Latent heat flux variability differs between datasets, and this is investigated using a bulk formula. It is found that discrepancies in wind speed change explain contrasting latent heat flux trends across datasets. The significant increase in wind speed of 0.26 m s−1 decade−1 over the tropical eastern Pacific in ERA-Interim is not reproduced by satellite or buoy observations or atmosphere-only climate model simulations, casting questions on the reliability of reanalysis-based surface fluxes over the tropical eastern Pacific.
Thèses sur le sujet "Reconstruction et simulations de flux"
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Negre, Delphine. « Rationalisation de l’Accès aux Produits Naturels Fongiques par une Approche OSMAC in silico : Cas d’étude avec la modélisation du métabolisme de Penicillium rubens ». Electronic Thesis or Diss., Nantes Université, 2024. http://www.theses.fr/2024NANU4038.
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Face à la résistance accrue aux antibiotiques menaçant la santé publique, la prospection de nouvelles molécules biologiquement actives est pressante. Les champignons filamenteux se distinguent par leur capacité à synthétiser une large gamme de produits naturels, sous l’influence de clusters de gènes biosynthétiques (BGC) qui orchestrent la production de métabolites spécialisés. Toutefois, de nombreux produits issus de ces BGCs n’ont pas encore été caractérisés et leur chimiodiversité demeure sous-explorée en raison de l’incapacité à activer l’ensemble de leur potentiel en laboratoire. L’approche OSMAC (One Strain Many Compound) permet de solliciter ce potentiel en variant les conditions de culture. Cependant, cette méthode reste complexe et coûteuse en raison de son caractère aléatoire et du grand nombre d’expérimentations nécessaires. L’optimisation de ces processus nécessite l’intégration de stratégies plus rationnelles et efficaces. A l’aide d’approches systémiques liées à la biologie des systèmes, les réseaux métaboliques à l’échelle du génome (GSMN) offrent une modélisation détaillée des voies métaboliques, des enzymes impliquées et des gènes associés, fournissant un aperçu précis du métabolisme. Dans ce cadre, nous proposons une stratégie alternative: l’OSMAC in silico. En reconstruisant un GSMN actualisé pour Penicillium rubens, nous avons pu étudier les réponses de son métabolisme sous divers scénarios nutritionnels. Cette modélisation a permis d’évaluer l’influence de différentes sources de carbone et d’azote sur sa croissance et la production de métabolites spécialisés, ouvrant ainsi de nouvelles perspectives pour optimiser la production de produits naturelsGiven the pressing issue of increasing antibiotic resistance threatening public health, new biologically active molecule research is urgent. Filamentous fungi are charcterised by their ability to synthesise a wide range of natural products, driven by biosynthetic gene clusters (BGCs) that orchestrate the production of specialised metabolites. However, many products derived from these BGCs remain uncharacterised, and their chemodiversity is underexplored due to the inability to activate their full potential in laboratory settings. The OSMAC (One Strain Many Compounds) approach seeks to harness this potential through culture condition variations. Nevertheless, this method remains complex and costly due to its randomness and vast number of experiments required. Therefore, optimising these processes needs the integration of more rational and efficient strategies. Using systems biology approaches, genome-scale metabolic networks (GSMNs) provide detailed modeling of metabolic pathways, involved enzymes, and associated genes, offering a precise overview of metabolism. In this context, we propose an alternative strategiy: in silico OSMAC. By reconstructing an updated GSMN for Penicillium rubens , we studied its metabolic responses under various nutritional scenarios. This modelling enabled us to assess the influence of different carbon and nitrogen sources on growth and the production of specialised metabolites, thereby opening new prospects for optimising the production of natural products
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Delestre, Olivier. « Simulation du ruissellement d'eau de pluie sur des surfaces agricoles ». Phd thesis, Université d'Orléans, 2010. http://tel.archives-ouvertes.fr/tel-00587197.
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L'objectif de ce travail est le développement d'un modèle et d'une méthode numérique adaptés à la simulation du ruissellement d'eau de pluie sur des surfaces agricoles. Pour cela, nous utilisons un système d'équations aux dérivées partielles pour les eaux peu profondes : le système de Saint Venant. La pluie et l'infiltration y sont pris en compte par l'ajout de termes source et le couplage avec un modèle d'infiltration. Le système étant hyperbolique et conservatif nous choisissons d'utiliser un schéma aux volumes finis avec reconstruction hydrostatique. Avec cette reconstruction nous obtenons un schéma permettant de traiter les équilibres stationnaires et les interfaces sec/mouillé dues aux événements pluvieux. Tout d'abord, nous effectuons une comparaison systématique de différents flux numériques, de différentes reconstructions d'ordre deux (MUSCL et ENO modifiées) et de différentes méthodes de traitement des frottements sur des solutions analytiques unidimensionnelles. Ces comparaisons nous permettent de choisir une méthode numérique adaptée à la simulation du ruissellement qui en outre capture les phénomènes de type roll-waves. Ensuite nous nous intéressons au traitement de la pluie et de l'infiltration à l'aide du modèle de Green-Ampt. Cette méthode généralisée en dimension deux est validée sur des résultats expérimentaux obtenus à l'INRA d'Orléans et à l'IRD. La méthode numérique choisie et validée a été implémentée dans FullSWOF_2D un logiciel libre écrit en C++ pour la simulation de ruissellement d'eau de pluie sur des surfaces agricoles.
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Ntemos, George. « GPU-accelerated high-order scale-resolving simulations using the flux reconstruction approach ». Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/59135.
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High-order methods in Computational Fluid Dynamics (CFD) offer a potential route towards the resolution of hitherto intractable fluid-dynamics problems in industry. The Flux Reconstruction (FR) approach provides a unifying framework for a number of popular high-order methods such as the Discontinuous Galerkin (DG). Its suitability for use on unstructured grids along with its ability to facilitate massively parallelised implementation on architectures such as GPUs provide a means to tackle computationally challenging flows around complex geometries. Such a flow can be found in the rod-aerofoil tandem configuration: Complex, unsteady flow structures generated by and interacting with more than a single solid body are central to a number of applications in the aerospace industry. The current thesis attempts to demonstrate the suitability of the FR approach in successfully simulating the flow around a rod-aerofoil configuration. The in-house CFD solver employed in the research is presented and the FR implementation analysed. Computational grid resolution issues arising from the rod-aerofoil problem are studied and a novel strategy for the stabilisation of the computation is implemented in the form of local entropy stability. The results obtained are analysed and conclusions are drawn on the utility of the FR approach in the absence of a sub-grid scale model (Implicit LES - under-resolved DNS). The present work confirms the utility of local entropy stability for the stabilisation of the rod-aerofoil simulation of aerofoil-chord based Reynolds number of Re=480, 000. It will also demonstrate that the under-resolved DNS setup that resulted in a computational cost of approximately six hours for a single flow pass over the aerofoil chord on 200 Nvidia P100 GPUs resulted in moderate success for a significant portion of the flow dynamics, which not adequately predicted when compared with experiment. The latter led to a series of useful conclusions. The core of the conclusions involved the apparent over-prediction of time-averaged velocity and momentum deficits across wakes and as well as over-prediction of turbulent intensities. An identification of the problematic areas is therefore given and potential alleviation techniques outlined.
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Ridel, Mélissa. « Reconstruction du flux d'énergie et recherche de squarks et gluinos dans l'expérience D0 ». Phd thesis, Université Paris Sud - Paris XI, 2002. http://tel.archives-ouvertes.fr/tel-00002927.
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DO est l'une des 2 expériences du collisionneur p-pbar du Fermi National Accelerator Laboratory près de Chicago. Après 5 années d'arrêt, le Run II a débuté en mars 2001. Il permettra d'explorer de nouveaux domaines de masses de squarks et de gluinos, particules supersymétriques dont la signature en jets et énergie transverse manquante est l'objet de ce travail. Mais, avant le démarrage, j'ai travaillé sur des améliorations hardware et software de la mesure de l'énergie, essentielle pour les jets et l'énergie transverse manquante.Une simulation des chaînes de lecture et de calibration de chaque voie du calorimètre a été réalisée. Son résultat dépend de 8 grandeurs caractéristiques qui ont été extraites par traitement du signal de mesures de réflectométrie temporelle. Elle permettra de définir une stratégie de calibration du calorimètre.
Une clusterisation des dépôts d'énergie calorimétrique a été réalisée (cel1NN) basée sur la cellule et non la tour et exploitant au maximum la granularité du calorimètre notamment en débutant dans le Sème compartiment électromagnétique, 4 fois plus granulaire que les autres. L'information longitudinale permet de séparer les particules électromagnétiques et hadroniques superposées. Ainsi, tous les éléments indispensables â la reconstruction individuelle des gerbes sont mis en oeuvre.
Puis, l'energy flow combine les clusters ce11NN et les traces reconstruites dans la cavité centrale pour conserver la meilleure mesure de l'énergie et améliorer ainsi la reconstruction du flux d'énergie de chaque événement.
L'efficacité des déclenchements calorimétriques actuels a été déterminée et utilisée pour une recherche de squarks et gluinos utilisant des événements Monte Carlo dans le cadre de mSUGRA. Une limite inférieure sur les masses des squarks et des gluinos qu'atteindra DO avec 100 pb-1 de luminosité est prédite â partir d'outils de reconstruction standards; elle pourra être améliorée grâce à l'utilisation de l'energy flow.
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Ridel, Mélissa. « Reconstruction du flux d'énergie et recherche de squarks et gluinos dans l'expérience DØ ». Paris 11, 2002. http://www.theses.fr/2002PA112101.
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DØ est l'une des 2 expériences du collisionneur pp ̃du Fermi National Accelerator Laboratory près de Chicago. Après 5 années d'arrêt, le Run II a débuté en mars 2001. Il permettra d'explorer de nouveaux domaines de masses de squarks et de gluinos, particules supersymétriques dont la signature en jets et énergie tranverse manquante est l'objet de ce travail. Mais, avant le démarrage, j'ai travaillé sur des améliorations hardware et software de la mesure de l'énergie, essentielle pour les jets et l'énergie transverse manquante. Une simulation des chaînes de lecture et de calibration de chaque voie du calorimètre a été réalisée. Son résultat dépend de 8 grandeurs caractéristiques qui ont été extraites par traitement du signal de mesures de réflectométrie temporelle. Elle permettra de définir une stratégie de calibration du calorimètre. Une clusterisation des dépôts d'énergie calorimétrique a été réalisée (cellNN) basée sur la cellule et non la tour et exploitant au maximum la granularité du calorimètre notamment en débutant dans le 3ème compartiment électromagnétique, 4 fois plus granulaire que les autres. L'information longitudinale permet de séparer les particules électromagnétiques et hadroniques superposées. Ainsi, tous les éléments indispensables à la reconstruction individuelle des gerbes sont mis en œuvre. Puis, l'energy flow combine les clusters cellNN et les traces reconstruites dans la cavité centrale pour conserver la meilleure mesure de l'énergie et améliorer ainsi la reconstruction du flux d'énergie de chaque événement. L'efficacité des déclenchements calorimétriques actuels a été déterminée et utilisée pour une recherche de squarks et gluinos utilisant des événements Monte Carlo dans le cadre de mSUGRA. Une limite inférieure sur les masses des squarks et des gluinos qu'atteindra DØ avec 100 pb^(-1) de luminosité est prédite à partir d'outils de reconstruction standard; elle pourra être améliorée grâce à l'utilisation de l'energy flowThe DØ experiment is located at the Fermi National Accelerator Laboratory on the TeVatron proton-antiproton collider. The Run II has started in march 2001 after 5 years of shutdown and will allow DØ extend its reach in squarks and gluinos searches, particles predicted by supersymmetry. In this work, I focussed on their decays that lead to signature with jets and missing transverse energy. But before the data taking started, I studied bath software and hardware ways to improve the energy measurement which is crutial for jets and for missing transverse energy. For each calorimeter channel, the physics and the calibration signal has been simulated based on a database of the 8 parameters that describe each channel. The parameters have been extracted from time reflectometry measurements. The calibration strategy can be defined using this simulation. Energy deposits in the calorimeter has been clustered with celINN, at the cellievei instead of the tower level. Efforts have been made to take advantage of the calorimeter granularity to aim at individual particles showers reconstruction. CellNN starts from the third floor which has a quadruple granulariry compared to the other floors. The longitudinal information has been used to detect electromagnetic and hadronic showers overlaps. Then, clusters and reconstructed tracks from the central detectors are combined and their energies compared. The better measurement is kept. Using this procedure allows to improve the reconstruction of each event energy flow. The efficiency of the current calorimeter triggers has been determined. They has been used to perform a Monte Carlo search analysis of squarks and gluinos in the mSUGRA framework. The lower bound that DO will be able to put on squarks and gluinos masses with a 100 pb^(-1) integrated luminosity has been predicted. The use of the energy flow instead of standard reconstruction tools will be able to improve this lower limit
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Marchand, Mathieu. « Flux financiers et endettement de l'État : simulations par modèle d'équilibre général calculable (MEGC) ». Thesis, Université Laval, 2007. http://www.theses.ulaval.ca/2007/24520/24520.pdf.
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Décossin, Étienne. « Ébullition et assèchement dans un lit de particules avec production interne de chaleur : premières expériences et simulations numériques en situation multidimensionnelle ». Toulouse, INPT, 2000. http://www.theses.fr/2000INPT004H.
Texte intégralRésumé :
Dans le contexte des études sur les accidents graves dans les centrales nucléaires, la démonstration de la capacité de refroidissement des lits de particules de corium, matériau résultant de la fusion du coeur et véhiculant la puissance résiduelle, est d'une grande importance. De nombreux travaux expérimentaux, essentiellement 1D, ont démontré l'existence d'un flux critique d'assèchement au-delà duquel le refroidissement des particules par l'ébullition de l'eau interstitielle n'est plus assuré. L'interprétation et la modélisation du phénomène reposent sur l'équation hydrodynamique d'Ergun, adaptée aux écoulements diphasiques par le biais des coefficients de perméabilité et passabilité relatives. Cette équation, malgré son manque de justification théorique, est aujourd'hui généralisée dans les modèles multidimensionnels pour simuler des situations représentatives des cas réacteurs. Un programme expérimental original a été élaboré dans le but de fournir des données de validation pour ces modèles. Constitué de billes en acier chauffées par induction, le lit poreux a un rapport d'aspect choisi pour capter des phénomènes bidimensionnels, en l'occurence des circulations convectives de liquide. Des premières mesures de flux critique d'assèchement ont été obtenues dans le cas homogène pour différentes hauteurs de lit et diamètres de billes. La confrontation des essais avec de simulations numériques montrent les limites actuelles de la modélisation. Ces premiers résultats montrent la nécessité de raffiner la représentation du phénomène d'assèchement tant au niveau des conditions aux limites que des équations de quantité de mouvement.
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Didorally, Sheddia. « Prévision des flux de chaleur turbulents et pariétaux par des simulations instationnaires pour des écoulements turbulents chauffés ». Thesis, Toulouse, ISAE, 2014. http://www.theses.fr/2014ESAE0015/document.
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Cette thèse s’inscrit dans le cadre de l’amélioration des prévisions aérothermiques qui suscite l’intérêt croissant des industriels aéronautiques. Elle consiste à évaluer l’apport des méthodes URANS avancées de type SAS dans la prévision des flux de chaleur turbulents et pariétaux pour des écoulements turbulents chauffés. Elle vise aussi à situer ces approches par rapports aux modèles URANS classiques de type DRSM et hybrides RANS/LES comme la ZDES. Une extension de l’approche SAS à un modèle DRSM a d’abord été proposé afin d’obtenir une meilleure restitution des tensions de Reynolds résolues et modélisées. Ce modale SAS-DRSM a été implanté dans le code elsA de l’ONERA. Nous avons ensuite évalué les approches SAS disponibles avec ce code sur la prévention d’écoulements aérothermiques rencontrés sur avion dans un compartiment de moteur. Ces études ont montré que les approches SAS améliorent la représentation des écoulements par rapport aux modèles URANS classiques. Elles aboutissent à des écoulements fortement tridimensionnels avec de nombreuses structures turbulentes. Ces structures induisent un mélange turbulent accru et donc une meilleure prévision du flux de chaleur pariétal. De plus, nos travaux ont situé les approches de type SAS comme des méthodes plus précises que les méthodes URANS classiques sans augmentation importante du coût de calcul. Les modèles SAS ne résolvent pas les plus petites structures caractéristiques du mouvement turbulent par rapport à la ZDES qui montre des prévisions supérieures. Le modèle SAS-RDSM offre néanmoins la meilleur alternative de type SAS. Enfin, l’étude du flux de chaleur turbulent semble retrouver le fait que l’hypothèse classique de nombre de Prandtl turbulent constat n’est pas valable dans toutes les zones de l’écoulementThe improvement of aerothermal predictions is a major concern for aeronautic manufacturers. In line with this issue, SAS approaches are assessed on the prediction of wall and turbulent heat fluxes for heated-turbulent flows. This study also aims at evaluating these advanced URANS methods in regard to DRSM models and hybrid RANS/LES approaches as ZDES. Firstly, we proposed to combine the SAS approach and a DRSM model in order to better reproduce both resolved and modelled Reynolds stresses. This new model, called SAS-DRSM, was implemented in ONERA Navier-Strokes code elsA. Unsteady simulations of two heated turbulent flows encountered in an aircraft engine compartment were then performed to evaluate all the SAS models available in the code. These numerical studies demonstrated that SAS approaches improve prediction of the flows compared to classical URANS models. They lead to full 3D flows with many turbulent structures. These structures favour turbulent mixing and thus induce a better prediction of the wall heat fluxes. Moreover, the numerical simulations showed that SAS methods are more accurate than classical URANS models without increasing significantly calculation costs. SAS approaches are not able to resolve the smallest turbulent structures in relation to ZDES which provides better predictions. Finally, the investigation of the turbulent heat flux suggested that the constant turbulent Prendtl number assumption, that is characteristic of classical URANS models, may not be valid in some regions of the flow
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Frasson, Thomas. « Flux de chaleur hétérogène dans des simulations de convection mantellique : impact sur la géodynamo et les inversions magnétiques ». Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALU027.
Texte intégralRésumé :
Le champ magnétique terrestre est généré par la convection du fer liquide dans le noyau, éléctriquementconducteur, produisant un effet dynamo. Ce processus, appelé géodynamo, maintientun champ magnétique depuis des milliards d’années. Les données paléomagnétiques montrent quele comportement de la géodynamo a changé au cours des temps géologiques. Ces changementsde comportement sont visibles à travers les variations de l’amplitude et de la stabilité du dipôlemagnétique. Les variations du flux de chaleur à la limite entre le noyau et le manteau (CMB) duesà la convection mantellique ont été suggérées comme un mécanisme capable d’entraîner un telchangement de comportement.Les modèles numériques de convection mantellique et de la géodynamo ont connu des améliorationssignificatives ces dernières années. Le couplage entre ces deux types de modèle peutdonner des indications sur la façon dont la géodynamo réagit aux variations de flux de chaleurà la CMB. Notre compréhension actuelle de ce couplage entre le manteau et le noyau est néanmoinsrestreinte par les limitations des modèles numériques. Du côté du manteau, l’orientationdu manteau par rapport à l’axe de rotation doit être mieux contrainte afin d’exploiter les récentessimulations reproduisant environ 1 Gyr de convection mantellique. Pour contraindre cette orientation,l’axe de plus grand moment d’inertie du manteau doit être aligné avec l’axe de rotation de laTerre, ce qui provoque des rotations du manteau appelées "true polar wander" (TPW). Du côté dunoyau, les simulations numériques sont encore loin du régime de paramètre de la Terre, et il n’estpas certain que le mécanisme d’inversion observé dans ces modèles soit pertinent pour le noyaude la Terre.Ce travail vise à mieux contraindre la façon dont les hétérogénéités de flux de chaleur à laCMB affectent la géodynamo. Dans une première partie, nous explorons l’impact du TPW surle flux de chaleur à la CMB en utilisant deux modèles de convection mantellique récemmentpubliés : un modèle contraint par une reconstruction de plaque et un second produisant de manièreautocohèrente un comportement de tectonique des plaques. Le géoïde est calculé pour corriger leTPW. Une alternative à la correction du TPW est utilisée pour le modèle contraint par la positiondes plaques en repositionnant simplement le manteau dans le référentiel paléomagnétique. Dansce modèle, l’axe de plus grand moment d’inertie n’est pas cohérent avec la position du dipôlemagnétique déduite du paléomagnétisme. Le TPW joue un rôle important dans la redistributiondu flux de chaleur, notamment à des échelles de temps courtes (≤ 10 Myr). Ces variations rapidesmodifient la distribution latitudinale du flux de chaleur à la CMB. Une analyse en composantesprincipales est effectuée pour obtenir les motifs de flux de chaleur dominant dans les modèles.Dans une deuxième partie, nous étudions l’impact des conditions hétérogènes de flux de chaleurau sommet du noyau dans des modèles de géodynamo qui s’étendent vers des régimes deparamètres plus proches de celui de la Terre que ce qui a été fait précédemment. L’effet de ladistribution du flux de chaleur en latitude est notamment étudié. Des motifs de flux complexes extraitsdes modèles de convection mantellique sont également utilisés. Nous montrons qu’un refroidissementéquatorial du noyau est le plus efficace pour déstabiliser le dipôle magnétique, tandisqu’un refroidissement polaire tend à stabiliser le dipôle. Les effets observés des flux de chaleurhétérogènes s’expliquent par la compatibilité entre les motifs de flux et les écoulements zonaux.Notamment, les motifs de flux de chaleur ont un effet plus modéré lorsque les écoulements zoiinaux vers l’ouest sont forts, avec une déstabilisation du dipôle seulement pour des amplitudesimprobables. Un paramètre contrôlant l’amplitude et la stabilité du dipôle magnétique, cohérentavec l’existence d’inversions magnétiques pour la Terre, est proposéThe Earth’s magnetic field is generated within the Earth’s core, where convective motions ofthe electrically conducting liquid iron result in a dynamo action. This process, called the geodynamo,has been maintaining a magnetic field for billion of years. Paleomagnetic evidence showsthat the behaviour of the geodynamo has changed during geological times. These behaviourchanges are visible through variations in the strength and stability of the magnetic dipole. Variationsin the heat flux at the core-mantle boundary (CMB) due to mantle convection have beensuggested as one possible mechanism capable of driving such a change of behaviour.Numerical models of mantle convection and of the geodynamo have made significant improvementsin the recent years. Coupling mantle convection models and geodynamo models cangive insights into how the geodynamo reacts to variations in the CMB heat flux. Our current understandingof this thermal coupling between the mantle and the core is nonetheless restricted bylimitations in numerical models on both the mantle and core side. On the mantle side, the orientationof the mantle with respect to the spin axis has to be better constrained in order to exploitrecent simulations reproducing about 1 Gyr of mantle convection. Constraining this orientationrequires to align the maximum inertia axis of the mantle with the spin axis of the Earth, causingsolid-body rotations of the mantle called true polar wander (TPW). On the core side, numericalsimulations are still far from the parameter regime of the Earth, and it is not clear whether thereversing mechanism observed in these models is relevant for the Earth’s core.This work aims at acquiring a more complete understanding of how lateral heterogeneitiesof the CMB heat flux affect the geodynamo. In a first part, we explore the impact of TPW onthe CMB heat flux using two recently published mantle convection models: one model drivenby a plate reconstruction and a second that self-consistently produces a plate-like behaviour. Wecompute the geoid in both models to correct for TPW. An alternative to TPW correction is used forthe plate-driven model by simply repositioning the model in the original paleomagnetic referenceframe of the plate reconstruction. We find that in the plate-driven mantle convection model, themaximum inertia axis does not show a long-term consistency with the position of the magneticdipole inferred from paleomagnetism. TPW plays an important role in redistributing the CMBheat flux, notably at short time scales (≤ 10 Myr). Those rapid variations modify the latitudinaldistribution of the CMB heat flux. A principal component analysis (PCA) is computed to obtainthe dominant CMB heat flux patterns in the models.In a second part, we study the impact of heterogeneous heat flux conditions at the top of thecore in geodynamo models that expands towards more Earth-like parameter regimes than previouslydone. We especially focus on the heat flux distribution between the poles and the equator.More complex patterns extracted from the mantle convection models are also used. We show thatan equatorial cooling of the core is the most efficient at destabilizing the magnetic dipole, while apolar cooling of the core tends to stabilize the dipole. The observed effects of heterogeneous heatflux patterns are explained through the compatibility of thermal winds generated by the heat fluxpattern with zonal flows. Notably, heat flux patterns have a more moderate effect when westwardzonal flows are strong, with a destabilization of the dipole only for unrealistically large amplitudes.A parameter controlling the strength and stability of the magnetic dipole that is consistentwith the reversing behaviour of the geodynamo is suggested.i
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Solminihac, Florence de. « Effets de perturbations magnétiques sur la dynamique de la barrière de transport dans un Tokamak : modélisation et simulations numériques ». Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4743/document.
Texte intégralRésumé :
Dans cette thèse nous étudions l'impact de perturbations magnétiques résonnantes sur la dynamique de la barrière de transport dans un tokamak. Pour cela nous avons réalisé des simulations numériques tridimensionnelles de turbulence dans le plasma de bord du tokamak. Nos simulations numériques ont reproduit les résultats expérimentaux observés dans différents tokamaks. Dans le régime de confinement amélioré (mode H), la barrière de transport n'est pas stable : elle effectue des oscillations de relaxation, qui partagent des caractéristiques communes avec les "modes localisés au bord'' (Edge Localized Modes, ELMs). Ces ELMs ont à la fois des avantages et des inconvénients. D'un côté, ils permettent d'évacuer les impuretés présentes dans le coe ur du plasma. Mais d'un autre côté, la charge thermique induite sur la paroi pendant un ELM peut endommager les matériaux de première paroi. Pour cette raison, ils doivent être contrôlés. Cette thèse s'inscrit dans le contexte du projet ITER actuellement en construction en France. Sur ITER, le contrôle des ELMs sera indispensable en raison de la quantité d'énergie évacuée. Parmi les différentes façons de contrôler les ELMs, les perturbations magnétiques résonnantes (Resonant Magnetic Perturbations, RMPs) semblent prometteuses. Ces perturbations magnétiques résonnantes sont créées par des bobines externes. Nous nous plaçons dans le cas du tokamak TEXTOR et nous considérons deux configurations pour les bobines externes : dans un premier temps, une perturbation magnétique résonnante comprenant plusieurs harmoniques, qui permet d'avoir une zone stochastique au bord du plasma lorsque les chaînes d'îlots magnétiques se superposentIn this PhD thesis we study the impact of resonant magnetic perturbations on the transport barrier dynamics in a tokamak. In this goal we have performed turbulence tridimensional numerical simulations in the edge plasma of a tokamak, which reproduced the experimental results observed in different tokamaks. In the improved confinement regime (H mode), the transport barrier is not stable : it does relaxation oscillations, which share common features with the ``Edge Localized Modes'' (ELMs). These ELMs both have advantages and drawbacks. On the one hand, they enable to push away the impurities present in the plasma core. But on the other hand, the thermal load induced on the wall during an ELM can damage the first wall materials. For this reason, they must be controlled. This PhD thesis belongs to the frame of the ITER project, which is today in construction in France. On ITER the ELMs control will be compulsory due to the quantity of energy released. Among the different ways of controlling the ELMs, the resonant magnetic perturbations (RMPs) seem promising. These resonant magnetic perturbations are created by external coils. We consider the TEXTOR tokamak case and we consider two configurations for the external coils : first, a resonant magnetic perturbation with several harmonics, which enables to have a stochastic zone at the plasma edge when the magnetic island chains overlap ; then, a resonant magnetic perturbation with a single harmonic, which therefore creates a single magnetic island chain. In this PhD thesis, we focus on the non-axisymmetric equilibrium created in the plasma by the resonant magnetic perturbation
Chapitres de livres sur le sujet "Reconstruction et simulations de flux"
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Yang, Qing-Qing, Jiu Luo, Dong-Chuan Mo, Shu-Shen Lyu et Yi Heng. « Fast Reconstruction of Transient Heat-Flux Distributions in a Laser Heating Process with Time-Space Adaptive Mesh Refinement ». Dans Computational and Experimental Simulations in Engineering, 1217–23. Cham : Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-27053-7_103.
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F. dos Santos, Jhennifer, Yasmim M.D. Lisboa, Elielson F.S. Barbosa, Lucas H.B. Santos, Allan R.A. Manito, Marcelo O. Silva et Wellington S. Fonseca. « Motor Monitoring and Analysis System (SMAM) as a Resource for Predictive Maintenance in Industrial Environments through Digital Twin and IIoT ». Dans Induction Motors - Latest Research and Applications [Working Title]. IntechOpen, 2024. http://dx.doi.org/10.5772/intechopen.1006914.
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The Motor Monitoring and Analysis System (SMAM) was developed as a tool that can help with the predictive maintenance of electric motors through Digital Twin (DT) and the Industrial Internet of Things (IIoT). To do this, SMAM has an embedded system made up of the ESP32 microcontroller and temperature, voltage and current sensors, in which the measurements taken are stored in the Firebase web database. It is worth noting that the sensors are calibrated using the least squares and linear regression mathematical methods, as well as using the ET-5062 energy analyzer as a reference to ensure that the measurement is reliable. In addition, strong coupling simulations are carried out in the Finite Element Method Magnetics (FEMM) software, which makes it possible to visualize the magnetic flux and the internal temperature of the motor by entering the measured current data. In this way, SMAM is a promising resource for the manufacturing environment.
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Rubin, Yoram. « Upscaling, Computational Aspects, and Statistics of the Velocity Field ». Dans Applied Stochastic Hydrogeology. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195138047.003.0011.
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This chapter deals with computing the velocity fields in heterogeneous media. This is a broad area, and we shall concentrate here on upscaling, on the spatial correlation pattern of the velocity, and on accuracy measures for techniques that compute velocity fields. Numerical simulations of velocity fields in heterogeneous media (Ababou et al., 1988, 1989; Bellin et al., 1992, 1994; Bellin and Rubin, 1996; Dykaar and Kitandis, 1992a,b; Hassan et al., 1998a,b; Salandin and Fiorotto, 1998) indicate that to capture accurately the effects of the spatial variability of the conductivity on the velocity field, the conductivity field should be modeled with high resolution. Techniques for generating highly detailed realizations of rock properties were reviewed earlier. Because of the huge level of detail included in these realizations, large-scale flow simulations can become computationally intensive. However, the need for fine detail varies over the aquifer. For example, a high level of detail is needed where the velocity field may vary rapidly, such as near wells, or over areas traversed by a contaminant plume, or for describing small-scale features which dominate the flow, such as high-conductivity channels. Coarsening the grid over areas where high resolution is unnecessary can reduce the computational effort. To be able to do that, a procedure is needed for assigning properties such as conductivity on a coarser scale which is more appropriate for simulation, while avoiding the loss of important details. Such a procedure is called upscaling (also scale-up). Upscaling assigns properties to blocks based on subgrid-scale heterogeneity. Upscaling leads to block-effective properties. Unlike effective properties, block-effective properties depend on the size of the block. In the limit of block dimensions much larger than the integral scale of the heterogeneity, the block-effective properties become equal to the media's effective properties. Unlike the case of effective conductivities, there is no consensus about the definition of block conductivity. For example, Rubin and Gomez-Hernandez (1990) defined the block conductivity as the coefficient of proportionality between the block-averaged flux and the gradient. Indelman and Dagan (1993a, b) stipulated that the block-effective conductivity should dissipate energy at a rate equal to the dissipation due to the small-scale heterogeneity.
Actes de conférences sur le sujet "Reconstruction et simulations de flux"
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Öhrle, Constantin, Ulrich Schäferlein, Manuel Keßler et Ewald Krämer. « Higher-order Simulations of a Compound Helicopter using Adaptive Mesh Refinement ». Dans Vertical Flight Society 80th Annual Forum & Technology Display, 1–19. The Vertical Flight Society, 2024. http://dx.doi.org/10.4050/f-0074-2018-12713.
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Higher-order methods and adaptive mesh refinement (AMR) have demonstrated their added value to numerical simulation of a variety of aerodynamic problems, including rotorcraft flow. Within this paper, the implementation of a higher-order spatial WENO (Weighted Essentially Non-Oscillatory) method for flux reconstruction and an AMR method for grid refinement into a comprehensive and approved rotorcraft simulation framework is discussed. A significant increase in computational efficiency by factor 15 can be achieved using higher-order methods. AMR allows a considerable reduction of required overall grid cells, and thus computational effort, to represent the occurring flow phenomena with equivalent accuracy. The rotorcraft simulation framework is applied to simulate a highly complex compound helicopter geometry with a variety of challenging phenomena. Flight mechanic trim and elastic blades are taken into account for a physical representation of the flight state. The benefit of the AMR technique in combination with the higher-order methods for an isolated rotor in hover and a complete helicopter configuration in cruise flight is investigated. A robust application of the AMR implementation is demonstrated, which shows a reduction of computational cost by 50% at high advance ratio cases without a noticeable loss of accuracy.
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Le Bras, Sophie, Hugues Deniau et Christophe Bogey. « A flux reconstruction technique for non-conforming grid interfaces in aeroacoustic simulations ». Dans 22nd AIAA/CEAS Aeroacoustics Conference. Reston, Virginia : American Institute of Aeronautics and Astronautics, 2016. http://dx.doi.org/10.2514/6.2016-2972.
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Miyaji, Koji. « On the Compressible Flow Simulations with Shocks by a Flux Reconstruction Approach ». Dans 20th AIAA Computational Fluid Dynamics Conference. Reston, Virigina : American Institute of Aeronautics and Astronautics, 2011. http://dx.doi.org/10.2514/6.2011-3057.
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Gnoffo, Peter. « Updates to Multi-Dimensional Flux Reconstruction for Hypersonic Simulations on Tetrahedral Grids ». Dans 48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition. Reston, Virigina : American Institute of Aeronautics and Astronautics, 2010. http://dx.doi.org/10.2514/6.2010-1271.
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LU, Yi, et William N. Dawes. « Large Eddy Simulations using High order Flux Reconstruction method on Hybrid Unstructured meshes ». Dans 52nd Aerospace Sciences Meeting. Reston, Virginia : American Institute of Aeronautics and Astronautics, 2014. http://dx.doi.org/10.2514/6.2014-0424.
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Lu, Yi, Kai Liu et W. N. Dawes. « Large Eddy Simulations for 3D Turbine Blades Using a High Order Flux Reconstruction Method ». Dans ASME Turbo Expo 2013 : Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gt2013-94707.
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During the last decades, the improvements of both computational ability and numerical schemes have stimulated increasing industrial interest in the use of Large Eddy Simulations (LES) for practical engineering flow problems. However, almost all current approches cannot treat complex geometries at affordable cost to enable LES of industrial problems. A robust, parallel and efficient solver using a general unstructured grid & based on high order flux reconstruction formulation, which uses local reconstruction, is compact and written in differential form without a mass matrix, was developed and has proved the ability to get accurate LES results but using RANS scale meshes. This work is aimed at using flux reconstruction method to perform Large Eddy Simulations for complex geometries in more robust and highly efficient way. Both explicit Runge-Kutta method and implicit LU-SGS method are implemented with improvements as solvers for better performance on boundary layer meshes including large aspect ratio cells. The current solver is ported to GPU architectures and speed up ratios of different order accuracy are presented in this work. A local reconstruction method is introduced to generate high order curved boundary from readily available first order meshes. The large eddy simulations for low pressure turbine blade and low pressure turbine blade with endwall are presented in this work, resolved with total number of degree of freedoms up to 34 million to chieve fourth order accuracy using limited computational resource. The results show that this approach has the potential to obtain LES results of real-geometry problems with affordable computational costs.
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Spiegel, Seth C., Michael R. Borghi et Dennis A. Yoder. « Large Eddy Simulations of a Single-Injector Cooling Flow Using the High-Order Flux Reconstruction Method ». Dans AIAA SCITECH 2022 Forum. Reston, Virginia : American Institute of Aeronautics and Astronautics, 2022. http://dx.doi.org/10.2514/6.2022-1813.
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Lu, Yi, Xin Yuan et W. N. Dawes. « Investigation of 3D Internal Flow Using New Flux-Reconstruction High Order Method ». Dans ASME Turbo Expo 2012 : Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-69270.
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The new godunov-type high order method via flux-reconstruction, are capable of unifiying several popular methods including the discontinuous Galerkin, staggered-grid multi-domain method, or the spectral difference/spectral volume methods into a single family. Compared to discontinuous galerkin method, this new method retain the arbitrary order and compact properties but written in differential form and without mass matrix. The flux-reconstrcution method using general unstructured 2D/3D mesh including triangles, quadrilaterals, tetrahedrons, pyramids, prisms and hexahedrons are implemented. Compared to discontinuous galerkin method, FR is differential form without any quandature, so it runs faster and is easier to implement on GPU to achieve higher speed up ratio. The present paper investigates three different solving methods for this new method in order to cut down the hugh computational cost and memory requirement for fully implicit methods. Explicit multi-stage Runge-Kutta, nonlinear Lower-Upper Symmetry Gauss-Seidel (LU-SGS) and generalized minimal residual (GMRES) with matrix-free preconditioning methods are implemented and all these three methods use p-multigrid to smooth low-frequency errors on lower order. The results of 2D steady-state external/internal viscous flows are presented and the convergence properties for different solving method are compared. Efficiency and robustness are improved through symmetric Gauss-Seidel (SGS) iterations as preconditioning, a remarkable feature of the present GMRES+SGS method is that the storage of the full Jacobian matrix can be eliminated and only its diagonal stored. A laplacian artificial viscosity is tested to capture shock in one element and performs well for this new high order method, an L2 projection method is used to improve the perfomance of aliasing error in conservative form. The one equation Spalart-Allmaras turbulence model is unsed to solve the Raynolds average navier-stokes equations. MPI is used for parallel simulations for ralatively complex 3D internal flow when using high order method. Compared to other high order methods, results in this paper show that Flux-Reconstruction methods with efficient solving method performs well for 2D/3D general unstructured mesh in wide range of reynorlds number, and is also potential for “real geometry” simulations.
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Poe, Nicole M. W., et D. Keith Walters. « A Non-Local Convective Flux Limiter for Upwind-Biased Finite Volume Simulations ». Dans ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30752.
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Finite volume methods on structured and unstructured meshes often utilize second-order, upwind-biased linear reconstruction schemes to approximate the convective terms, in an attempt to improve accuracy over first-order methods. Limiters are employed to reduce the inherent variable over- and under-shoot of these schemes; however, they also can significantly increase the numerical dissipation of a solution. This paper presents a novel non-local, non-monotonic (NLNM) limiter developed by enforcing cell minima and maxima on dependent variable values projected to cell faces. The minimum and maximum values for a cell are determined primarily through the recursive reference to the minimum and maximum values of its upwind neighbors. The new limiter is implemented using the User Defined Function capability available in the commercial CFD solver Ansys FLUENT. Various simple test cases are presented which exhibit the NLNM limiter’s ability to eliminate non-physical oscillations while maintaining relatively low dissipation of the solution. Results from the new limiter are compared with those from other limited and unlimited second-order upwind (SOU) and first-order upwind (FOU) schemes. For the cases examined in the study, the NLNM limiter was found to improve accuracy without significantly increasing solution convergence rate.
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Roglic, H., S. D. Kwak, J. H. Henry, G. A. Ateshian, W. G. Rodkey, J. R. Steadman et V. C. Mow. « Adhesions of the Patellar and Quadriceps Tendons : Mathematical Model Simulations ». Dans ASME 1997 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/imece1997-0328.
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Abstract Following knee surgery, especially after anterior cruciate ligament (ACL) reconstruction, a small percentage of patients complain about significantly decreased patellar mobility accompanied by anterior knee pain, sometimes severe. The limited mobility and knee pain usually do not disappear even with aggressive physical therapy. Arthroscopic exploration of these knees reveals a closure of the patellar tendon-tibial (PTT) interval, i.e., severe fibrous adhesion of the patellar tendon to the anterior aspect of the tibia, the formation of fibrous tissue between the quadriceps tendon and the femur, and a ‘closed-off’ suprapatellar pouch. Other investigators have also noted such adhesion (Paulos et al., 1987 & 1994; Jacobson et al., 1989), and Hughston (1985) attributed the tendon adhesion to the scarring of infrapatellar and suprapatellar fat pad caused by the surgery. While the adhesions are important clinical problems associated with knee surgery, no study to date, other than our experimental study on patellar tendon contracture, has quantitatively investigated the effect of these adhesions on knee kinematics and contact forces (Ahmad et al., 1997). In this study, we use a 3-D mathematical model of the knee joint to analyze the effects of the patellar tendon adhesion (PA) to the anterior tibia, and the quadriceps tendon adhesion (QA) to the anterior femur. Our objective, therefore, is to demonstrate the effects of these types of post-operative adhesions on patellofemoral joint mechanics.
Rapports d'organisations sur le sujet "Reconstruction et simulations de flux"
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Ridel, Melissa. Reconstruction du Flux d'Energie et Recherche de Squarks et Gluinos dans l'Experience D0. Office of Scientific and Technical Information (OSTI), janvier 2002. http://dx.doi.org/10.2172/1420957.
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