Academic literature on the topic 'CFD model Code_Saturne'
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Journal articles on the topic "CFD model Code_Saturne":
1
Maison, Alice, Cédric Flageul, Bertrand Carissimo, Yunyi Wang, Andrée Tuzet, and Karine Sartelet. "Parameterizing the aerodynamic effect of trees in street canyons for the street network model MUNICH using the CFD model Code_Saturne." Atmospheric Chemistry and Physics 22, no. 14 (July 20, 2022): 9369–88. http://dx.doi.org/10.5194/acp-22-9369-2022.
Abstract:
Abstract. Trees provide many ecosystem services in cities such as urban heat island reduction, water runoff limitation, and carbon storage. However, the presence of trees in street canyons reduces the wind velocity in the street and limits pollutant dispersion. Thus, to obtain accurate simulations of pollutant concentrations, the aerodynamic effect of trees should be taken into account in air quality models at the street level. The Model of Urban Network of Intersecting Canyons and Highways (MUNICH) simulates the pollutant concentrations in a street network, considering dispersion and physico-chemical processes. It can be coupled to a regional-scale chemical transport model to simulate air quality over districts or cities. The aerodynamic effect of the tree crown is parameterized here through its impact on the average wind velocity in the street direction and the vertical transfer coefficient associated with the dispersion of a tracer. The parameterization is built using local-scale simulations performed with the computational fluid dynamics (CFDs) code Code_Saturne. The two-dimensional CFD simulations in an infinite street canyon are used to quantify the effect of trees, depending on the tree characteristics (leaf area index, crown volume fraction, and tree height to street height ratio) using a drag porosity approach. The tree crown slows down the flow and produces turbulent kinetic energy in the street, thus impacting the tracer dispersion. This effect increases with the leaf area index and the crown volume fraction of the trees, and the average horizontal velocity in the street is reduced by up to 68 %, while the vertical transfer coefficient by up to 23 % in the simulations performed here. A parameterization of these effects on horizontal and vertical transfers for the street model MUNICH is proposed. Existing parameterizations in MUNICH are modified based on Code_Saturne simulations to account for both building and tree effects on vertical and horizontal transfers. The parameterization is built to obtain similar tree effects (quantified by a relative deviation between the cases without and with trees) between Code_Saturne and MUNICH. The vertical wind profile and mixing length depend on leaf area index, crown radius, and tree height to street height ratio. The interaction between the trees and the street aspect ratio is also considered.
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Maison, Alice, Cédric Flageul, Bertrand Carissimo, Andrée Tuzet, and Karine Sartelet. "Parametrization of Horizontal and Vertical Transfers for the Street-Network Model MUNICH Using the CFD Model Code_Saturne." Atmosphere 13, no. 4 (March 25, 2022): 527. http://dx.doi.org/10.3390/atmos13040527.
Abstract:
Cities are heterogeneous environments, and pollutant concentrations are often higher in streets compared with in the upper roughness sublayer (urban background) and cannot be represented using chemical-transport models that have a spatial resolution on the order of kilometers. Computational Fluid Dynamics (CFD) models coupled to chemistry/aerosol models may be used to compute the pollutant concentrations at high resolution over limited areas of cities; however, they are too expensive to use over a whole city. Hence, simplified street-network models, such as the Model of Urban Network of Intersecting Canyons and Highways (MUNICH), have been developed. These include the main physico-chemical processes that influence pollutant concentrations: emissions, transport, deposition, chemistry and aerosol dynamics. However, the streets are not discretized precisely, and concentrations are assumed to be homogeneous in each street segment. The complex street micro-meteorology is simplified by considering only the vertical transfer between the street and the upper roughness sublayer as well as the horizontal transfer between the streets. This study presents a new parametrization of a horizontal wind profile and vertical/horizontal transfer coefficients. This was developed based on a flow parametrization in a sparse vegetated canopy and adapted to street canyons using local-scale simulations performed with the CFD model Code_Saturne. CFD simulations were performed in a 2D infinite street canyon, and three streets of various aspect ratios ranging from 0.3 to 1.0 were studied with different incoming wind directions. The quantities of interest (wind speed in the street direction and passive tracer concentration) were spatially averaged in the street to compare with MUNICH. The developed parametrization depends on the street characteristics and wind direction. This effectively represents the average wind profile in a street canyon and the vertical transfer between the street and the urban roughness sublayer for a wide range of street aspect ratios while maintaining a simple formulation.
3
Lin, Chao, Yunyi Wang, Ryozo Ooka, Cédric Flageul, Youngseob Kim, Hideki Kikumoto, Zhizhao Wang, and Karine Sartelet. "Modeling of street-scale pollutant dispersion by coupled simulation of chemical reaction, aerosol dynamics, and CFD." Atmospheric Chemistry and Physics 23, no. 2 (January 26, 2023): 1421–36. http://dx.doi.org/10.5194/acp-23-1421-2023.
Abstract:
Abstract. In the urban environment, gas and particles impose adverse impacts on the health of pedestrians. The conventional computational fluid dynamics (CFD) methods that regard pollutants as passive scalars cannot reproduce the formation of secondary pollutants and lead to uncertain prediction. In this study, SSH-aerosol, a modular box model that simulates the evolution of gas, primary and secondary aerosols, is coupled with the CFD software, OpenFOAM and Code_Saturne. The transient dispersion of pollutants emitted from traffic in a street canyon is simulated using the unsteady Reynolds-averaged Navier–Stokes equations (RANS) model. The simulated concentrations of NO2, PM10, and black carbon (BC) are compared with field measurements on a street of Greater Paris. The simulated NO2 and PM10 concentrations based on the coupled model achieved better agreement with measurement data than the conventional CFD simulation. Meanwhile, the black carbon concentration is underestimated, probably partly because of the underestimation of non-exhaust emissions (tire and road wear). Aerosol dynamics lead to a large increase of ammonium nitrate and anthropogenic organic compounds from precursor gas emitted in the street canyon.
4
Grecu, I. S., G. Dunca, D. M. Bucur, and M. J. Cervantes. "URANS numerical simulations of pulsating flows considering streamwise pressure gradient on asymmetric diffuser." IOP Conference Series: Earth and Environmental Science 1079, no. 1 (September 1, 2022): 012087. http://dx.doi.org/10.1088/1755-1315/1079/1/012087.
Abstract:
Abstract The paper focuses on implementing the wall model developed by Manhart, in Reynolds Averaged Navier - Stokes (RANS) turbulence models used in the field of Computational Fluid Dynamics (CFD). This wall model considers the influence of the streamwise pressure gradient in addition to the existing wall models used in the usual CFD codes. In the present work, two RANS numerical simulations are carried out using the k-ω Shear Stress Transport (SST) turbulence model on an asymmetric diffuser geometry. One numerical simulation is carried out using the implementation of the Manhart wall model in the k-ω SST turbulence model, and the other numerical simulation is performed using the standard formulation of the k-ω SST turbulence model. The numerical simulations carried out using the Manhart wall model and the standard formulation of the k-ω SST are compared with experimental measurements made on the asymmetric diffuser experimental installation. The numerical simulations are carried out using a free, open-source CFD tool, Code_Saturne. The comparisons between numerical simulations and the experimental data are in good agreement in the boundary layer of the flow inside the diffuser. The Manhart wall model had a faster convergence resulting in a shorter simulation time.
5
Lacome, Jean-Marc, Guillaume Leroy, Lauris Joubert, and Benjamin Truchot. "Harmonisation in Atmospheric Dispersion Modelling Approaches to Assess Toxic Consequences in the Neighbourhood of Industrial Facilities." Atmosphere 14, no. 11 (October 26, 2023): 1605. http://dx.doi.org/10.3390/atmos14111605.
Abstract:
In the land use planning framework in the neighbourhood of industrial facilities, the current approach to predicting the consequences of massive toxic gas releases is generally based on Gaussian or integral models. For many years, CFD models have been more and more used in this context, in accordance with the development of high-performance computing (HPC). The present paper focuses on harmonising input data for atmospheric transport and dispersion (AT&D) modelling between the widely used approaches. First, a synthesis of the practice’s harmonisation for atmospheric dispersion modelling within the framework of risk assessment is presented. Then, these practices are applied to a large-scale INERIS ammonia experimental release. For illustration purposes, the impact of the proposed harmonisation will be evaluated using different approaches: the SLAB model, the FDS model, and the Code_Saturne model. The two main focuses of this paper are the adaptation of the source term dealing with a massive release and the wind flow modelling performance using an experimental signal for CFD model inflow. Finally, comparisons between the modelling and experimental results enable checking the consistency of these approaches and reinforce the importance of the input data harmonisation for each AT&D modelling approach.
6
Madejski, Paweł. "Coal combustion modelling in a frontal pulverized coal-fired boiler." E3S Web of Conferences 46 (2018): 00010. http://dx.doi.org/10.1051/e3sconf/20184600010.
Abstract:
The paper presents results of numerical modelling of pulverized coal combustion process in the coal-fired boiler. In the numerical model, coal combustion process includes particle heating, devolatilization, char combustion, as well as turbulent flow and radiative heat transfer was modelled. Presented modelling results were carried out using the Open Source CFD code - Code_Saturne created and developed by EDF R&D and were used to study the combustion of coal in power plant boiler with the objective of simulating the operational conditions and identifying factors of inefficiency. The behaviour of the flow of air and pulverized coal through the burners was modelled, and the three-dimensional flue gas flow through the combustion chamber and heat exchangers was reproduced in the simulation.
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Gupta, Nikita, Nishant Bhardwaj, Gulam Muhammad Khan, and Vivek Dave. "Global Trends of Computational Fluid Dynamics to Resolve Real World Problems in the Contemporary Era." Current Biochemical Engineering 6, no. 3 (December 28, 2020): 136–55. http://dx.doi.org/10.2174/2212711906999200601121232.
Abstract:
Background: Computational fluid dynamics (CFD) came into existence with great success, thereby replacing the traditional methods used to simulate the problems related to the flow of fluid. First CFD utilitarian was introduced to the world in 1957, which was developed by a team at Los Alamos National Lab. For tremendous performance and to meet the expected results with ease for modern process conditions, engineers are now more inclined towards the use of simulation software rather than traditional methods. Hence, in the current scenario with the advancement of computer technologies, “CFD is recognized as an excellent tool for engineers to resolve real-world problems.” Introduction: CFD is defined as a branch of fluid dynamics which involves the use of numerical analysis and data structure to solve complications related to the flow of fluids (gasses or liquids). CFD is based on three major principles that are mass conservation, Newton's second law, and energy conservation. CFD has extended to a number of applications at an alarming rate in every field such as in aerospace, sports, food industry, engineering, hydraulics, HVAC (Heating, Ventilating, and Air conditioning), automotive, environmental, power generation, biomedical, pharmaceutical, and many more. Hence, a number of software like ANSYS, Open Foam, SimScale, Gerris, Auto desk simulation, Code_Saturne, etc, are beneficial in order to execute the operations, and to find the solution of realworld problems within a fraction of seconds. Methods: CFD analysis involves three major steps; pre-processing, solution, and post-processing. Preprocessing deals with defining model goals, identification of domain, designing, and creating the grid. Solution involves setting up the numerical model, computing, and monitoring the solution; whereas, post-processing includes results of the examination and revision of the model. Results: The review includes current challenges about the computational fluid dynamics. It is relevant in different areas of engineering to find answers for the problems occurring globally with the aid of a number of simulation-based software hereby, making the world free from complex problems in order to have a non-complicated scenario. Conclusion: Computational fluid dynamics are relevant in each, and every kind of problem related to the fluid flow, either existing in the human body or anywhere. In the contemporary era, there are enormous numbers of simulation-based software, which provide excellent results with just one click, thereby resolving the problems within microseconds. Hence, we cannot imagine our present and upcoming future without CFD, which has ultimately made the execution of work easier, leaving behind non-complicating scenarios. Lastly, we can conclude that “CFD is a faster, smarter, and lighter way in designing process.”
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Liu, Bo, Shuisheng He, Charles Moulinec, and Juan Uribe. "A Numerical Study of Turbulent Upward Flow of Super Critical Water in a 2 × 2 Rod Bundle With Nonuniform Heating." Journal of Nuclear Engineering and Radiation Science 6, no. 3 (June 5, 2020). http://dx.doi.org/10.1115/1.4046260.
Abstract:
Abstract This work is part of a benchmarking exercise organized by an IAEA in supercritical water-cooled reactor (SCWR) thermal-hydraulics aimed at improving the understanding and prediction accuracy of the thermal-hydraulic phenomena relevant to SCWRs. An experiment carried out using a 2 × 2 SCWR bundle at University of Wisconsin-Madison was modeled using an open-source computational fluid dynamics (CFD) code—Code_Saturne. The k–ω shear stress transport (SST) model was used to account for the buoyancy-aided turbulent flow in the fuel channel. Significant heat transfer deterioration (HTD) was observed in the boundary layer, which is commonly expected to occur in buoyancy-aided flows. For comparison, simulations were also conducted using ansysfluent with similar model setups.
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Wang, L., Y. Fournier, J. F. Wald, and Y. Mesri. "A graph neural network-based framework to identify flow phenomena on unstructured meshes." Physics of Fluids 35, no. 7 (July 1, 2023). http://dx.doi.org/10.1063/5.0156975.
Abstract:
Driven by the abundant data generated from computational fluid dynamics (CFD) simulations, machine learning (ML) methods surpass the deterministic criteria on flow phenomena identification in the way that they are independent of a case-by-case threshold by combining the flow field properties and the topological distribution of the phenomena. The current most popular and successful ML models based on convolutional neural networks are limited to structured meshes and unable to directly digest the data generated from unstructured meshes, which are more widely used in real industrial CFD simulations. We proposed a framework based on graph neural networks with the proposed fast Gaussian mixture model as the convolution kernel and U-Net architecture to detect flow phenomena based on a graph hierarchy generated by the algebraic multigrid method embedded in the open-source CFD solver, code_saturne. We demonstrate the superiority of the proposed kernel and U-Net architecture, along with the generality of the framework to unstructured mesh and unseen case, on detecting the vortices once trained on a single backward-facing step case. Our proposed framework can be trivially extended to detect more flow phenomena in three dimensional cases, which is ongoing work.
10
Vivaldi, Daniele, and Guillaume Ricciardi. "Optimizing Coupled Fluid-Structure Simulations for Nuclear Relevant Geometries." Journal of Pressure Vessel Technology, May 21, 2024, 1–45. http://dx.doi.org/10.1115/1.4065584.
Abstract:
Abstract The numerical simulation of fluid-structure interactions has gained interest to study flow-induced vibrations. Nevertheless, the high computational resources required by such simulations can represent a significant limitation for their application to industrial configurations. Therefore, simplified modelling approaches, when physically applicable, can represent an interesting compromise. This can be the case of slender structures (tubes, rods) often encountered in nuclear power plants. In this paper, an Euler-Bernoulli beam finite element model is implemented inside the CFD code code_Saturne. With the goal of finding CFD methods less expensive than Large Eddy Simulations (LES), URANS and hybird URANS/LES approaches are considered. The resulting fluid-structure model is able to calculate the vibration response of cantilever beams under a fluid flow, avoiding the necessity of CFD-FEM code coupling. The first part of the paper describes the model and its implementation: it allows to perform 2-way explicit fluid-structure coupling, using the Arbitrary Lagrangian-Eulerian approach to account for the structure deformations. Validation test cases are presented in the second part: first, the model is validated in terms of frequency, added mass and damping for a cylinder vibrating in static air and water; then, the model is validated towards the vortex-induced resonance and lock-in mechanisms for a cylinder subjected to water cross-flow. The model is then applied to a real experimental configuration of two in-line cylinders in water cross-flow: the calculated vibrations are found to be in good agreement with the experimental measurements.
Dissertations / Theses on the topic "CFD model Code_Saturne":
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Alam, Boulos. "Modélisation numérique de la turbulence et de la dispersion atmosphérique par faibles vents en milieu urbain." Electronic Thesis or Diss., université Paris-Saclay, 2023. https://www.biblio.univ-evry.fr/theses/2023/interne/2023UPAST179.pdf.
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Cette thèse se situe dans le contexte de la modélisation de la dispersion atmosphérique, en particulier en présence de vents faibles. Les sources de pollution atmosphérique, souvent situées près du sol et influencées par des obstacles complexes, engendrent des concentrations élevées de polluants à proximité, ce qui se traduit par des fluctuations significatives de ces concentrations. Les vents faibles, généralement associés à des conditions atmosphériques stables, posent un défi particulier en matière de modélisation de la dispersion des polluants, nécessitant une analyse approfondie des donnéesmétéorologiques et une adaptation des modèles de prédiction. Afin de relever ce défi complexe, l'utilisation de la Dynamique des Fluides Numérique (CFD) est incontournable, même si des recherches supplémentaires sont nécessaires pour valider son efficacité dans le champ proche des sources et en présence de vents faibles. Le logiciel Code_Saturne® (EDF R&D) est sélectionné en raison de sonefficacité avérée dans la simulation de la dispersion de polluants atmosphériques. Cette thèse se décompose en trois phases distinctes : la première phase se concentre sur les fondements de la dispersion atmosphérique, en explorant l'impact de différents paramètres tels que la structure de la couche limite atmosphérique, la turbulence atmosphérique et la stabilité de l'atmosphère. Ces éléments jouent un rôle crucial dans la manière dont les polluants se dispersent dans l'air. La deuxièmephase détaille la méthodologie utilisée dans Code_Saturne pour effectuer les simulations, notamment les modèles de turbulence utilisés et les critères d'évaluation de ces modèles. En plus des modèles isotropes classiques, cette recherche se penche sur l'utilisation de modèles de turbulence anisotropes pour étudier la dispersion dans divers contextes. La troisième phase de la thèse se concentre sur l'évaluation de différents modèles de turbulence et de corrélations vitesse-scalaire à l'aide d'observations effectuées en milieu urbain dans des conditions atmosphériques neutres et stables.Enfin, la dernière phase de la recherche explore les conditions de vent faible et stable, caractérisées généralement par des vitesses de vent inférieures à 2 m/s et des variations aléatoires du vent. Cette phase examine les méandres dans la dispersion des polluants et évalue les limites des modèles analytiques et CFD pour prédire la concentration dans de telles condi- tions. À cet effet, un modèle URANS est développé et évalué. Enfin, une méthode gaussienne segmentée est élaborée pour comparer les résultats aux prédictions CFD et aux observations sur le terrainThis thesis is situated in the context of atmospheric dispersion modeling, particularly in the presence of low winds. Atmospheric pollution sources, often located near the ground and influenced by complex obstacles, generate high concentrations of pollutants nearby, resulting in significant concentration fluctuations. Low winds, typically associated with stable atmospheric conditions, pose a specific challenge in modeling pollutant dispersion, requiring a thorough analysis of meteorological data and adaptation of prediction models. To address this complex challenge, the use of Computational Fluid Dynamics (CFD) is necessary, although further research is needed to validate its effectiveness in the near-field and in the presence of low winds. The Code_Saturne® software (EDF R&D) is selected due to its proven efficiency in simulating atmospheric pollutant dispersion. This thesis is divided into three distinct phases : the first phase focuses on the fundamentals of atmospheric dispersion, exploring the impact of various parameters such as the atmospheric boundary layer structure, atmospheric turbulence, and atmospheric stability. These elements play a crucial role in how pollutants disperse in the air. The second phase details the methodology used in Code_Saturne for conducting simulations, including the turbulence models employed and the criteria for evaluating these models. In addition to traditional isotropic models, this research investigates the use of anisotropic turbulence models to study dispersion in various contexts. The third phase of the thesis concentrates on the evaluation of different turbulence models and velocity-scalar correlations using observations conducted in urban environments under neutral and stable atmospheric conditions. Finally, the last phase of the research explores conditions of low and stable winds, typically characterized by wind speeds below 2 m/s and random wind variations. This phase examines the meandering patterns in pollutant dispersion and assesses the limitations of analytical and CFD models in predicting concentration in such conditions. To this end, a URANS model is developed and evaluated. Ultimately, a segmented Gaussian method is devised to compare the results with CFD predictions and field observations
Conference papers on the topic "CFD model Code_Saturne":
1
Xu, Tingting, Jiesheng Min, Serge Bellet, Richard Howard, Dominique Alvarez, and Guofei Chen. "Design Investigation on Flow Diffuser With Code_Saturne: CFD Simulation Analysis." In 2017 25th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/icone25-67767.
Abstract:
The flow rate distribution at the entrance of the core plays a key role for reactor design since it has important implications for the performance, and efficient safety of a nuclear reactor. When the coolant passes from the downcomer to the core, it changes direction due to the inertia force and the curvature of the bottom vessel head. The internal components inside lower plenum work to homogenize the flow distribution. Their purpose is to prevent the formation of instabilities and the creation of vortices due to the flow reversal. In the frame of EDF’s new reactor design there is a desire to identify an optimal flow diffuser. The future intention is to study five different types of flow diffuser including EPR, VVER, Konvoï, APR+ and Westinghouse to look at the pros and cons of each design. The authors underline that the geometries of each Reactor Pressure Vessel (RPV) and associated diffuser device are quite different therefore a generic form needs to be used to make an equivalent comparison. The goal of the present work is to find the optimal mesh refinement and associated numerical parameters for the simulation of the lower plenum flow. This work is a preliminary step for a future study to compare existing diffuser concepts. Thus in the future work only the section containing the flow diffuser structure will be changed. The PIRT methodology is applied to better define the physical phenomena and key parameters that will influence the flow distribution at the entrance of the core. In order to better understand the fluid distribution and the function of the diffuser component, 3D computational fluid dynamics (CFD) simulations are launched to improve our knowledge on the flow pattern inside the lower plenum. Both the geometry and mesh are generated by Salomé1. Simulations are carried out using Code_Saturne2, an EDF in-house open-source CFD code. The generic test case is a 1/5 scale EDF “BORA” 4 loop mock-up with a flow rate of 0.1 m3/s injected into each cold leg. The unsteady flow algorithm with standard k-epsilon turbulence model has been used with a full explicit meshing except for the reactor core where a porous approach is adopted. The physical time for each calculation case is 5s for a converged simulation. Mesh sensitivity tests have been carried out ranging from 8 million cells to 28 million cells. A mesh of 22 million cells is found to provide the most appropriate balance between simulation quality and feasibility. Due to the size of the simulations, high performance computers are necessary to provide timely results. The results indicate that CFD can provide extra capacity to engineers for reactor design to evaluate the pros and cons of different existing diffuser concepts.
2
Liu, Jiawei, Puzhen Gao, Tingting Xu, Jiesheng Min, and Guofei Chen. "Numerical Simulation of Flow Field Inside Reactor Upper Plenum for PWR With Code_Saturne." In 2017 25th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/icone25-68008.
Abstract:
Flow characteristic in upper plenum has a strong influence on reactor functional margin and rod cluster control assembly (RCCA) guide tube wear. Upper plenum flow governs loops flow rate measurement via hot leg temperature which has also an influence on the reactor protection system. For RCCA guide tube wear, it appears in operation with RCCA flow-induced vibration, leading to its replacement. It is important to know the flow condition in the upper plenum, and in particular the outlet. Existing Generation III reactors have their own specialties on the design. Comparison between current technologies is a good way for better understanding on the key structure design for the upper plenum. In this paper, simplified models based on upper plenum structure of Korean advanced pressurized water reactor (PWR) and Westinghouse design AP1000 are constructed and meshed with a volume around 6 million cells to obtain a 3-dimensional global and local flow distributions inside the upper plenum and to characterize the vital flow features for reactor safety. The Navier-Stokes equations are solved with standard k-ε turbulence model by using EDF in-house open source computational fluid dynamic (CFD) software: Code_Saturne. Through calculations, pressure and velocity distributions are obtained, axial and lateral variations have been analyzed. Compared with APR1400, it can be observed that for the design of AP1000, the rotational flow entrained in the edge of upper plenum and high velocity area due to the hot leg suction effect contribute to the relatively lower local pressure, and may have an impact on the drop velocity of control rod.
3
Chen, Ru, Ronghao Liang, Lu Zhou, and Jiesheng Min. "A Sensitivity Analysis of Condensation Phenomena for a Passive Containment Cooling System by Using Code_Saturne Coupled With OpenTURNS." In 2022 29th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/icone29-92164.
Abstract:
Abstract Computation-expensive problems have become more common in nuclear industry, originating from expensive analysis with the aim of reaching high accuracy. To overcome this challenge, surrogate modelling techniques are often proposed. Passive containment cooling system (PCCS) is an essential pattern to ensure the containment integrity in the case of accidental conditions for AP600 reactor, so determination of the most influential parameter as regards the heat transfer rate is of great significance to the optimization design and security analysis of nuclear power plants. This paper contributes to uncertainty quantification in condensation phenomena for PCCS. The purpose is to create a surrogate model instead of a deterministic model for sensitivity analysis on the account of saving computational time. The case used is an experiment carried out in 1998 for which the data is publicly available and was selected here as a showcase of the meta-model construction. In this paper, the database conducted by Anderson in 1998 is used to validate the computational fluid dynamics (CFD) model. By coupling Open-source CFD code code_saturne and uncertainty analysis code OpenTURNS from the SALOME Platform, a representative sample of input and output parameters is obtained using the design of experiments (DoE) technique. Thus, a surrogate model, including kriging and polynomial chaos metamodel, is constructed. In this way, sensitivity analysis of condensing efficiency is performed, which demonstrates the propagation of modeling uncertainty of condensation phenomena.
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Benhamadouche, S., P. Moussou, and C. Le Maitre. "CFD Estimation of the Flow-Induced Vibrations of a Fuel Rod Downstream a Mixing Grid." In ASME 2009 Pressure Vessels and Piping Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/pvp2009-78054.
Abstract:
Turbulent-induced vibrations of fuel assemblies in PWR power plants is a potential cause of deformation and of fretting wear damage. Because of the complexity of a 17 × 17 rod assembly with a length exceeding four meters, the prediction of its vibrations is still a challenging task as regards computer simulation. The Large Eddy Simulation (LES) technique provides the instantaneous pressure and velocity fields inside the fluid as well as the shear stress and the pressure along the walls. EDF inhouse open source CFD tool Code_Saturne is used in the present work with a 8 million cells grid to compute the flow along four sub-channels all around one fuel rod by taking into account only one mixing grid. The computations are carried out on 1024 processors of a BlueGene/L supercomputer. Hence, the overall turbulent excitation upon one single rod is estimated numerically, taking into account the specific influence of the deflectors. As regards the structure, using the forces provided by the CFD computation, a linear model of the rod based on Euler beam theory and simplified boundary conditions is proposed. The first natural modes of the structure are hence obtained, and the modal forces are estimated using the standard techniques of modal projection and joint acceptance. Estimations of the vibration amplitude of rod induced by the local flow are finally obtained, using simplified expressions of the added mass and of the damping coefficient. The amplitudes are significant for the first mode essentially, and reach a value of the order of the μm, with a maximum around 6 μm.
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Pe´niguel, Christophe, Marc Sakiz, Sofiane Benhamadouche, Jean-Michel Stephan, and Carine Vindeirinho. "Presentation of a Numerical 3D Approach to Tackle Thermal Striping in a PWR Nuclear T-Junction." In ASME 2003 Pressure Vessels and Piping Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/pvp2003-2191.
Abstract:
This paper presents a numerical study to tackle thermal striping phenomena occuring in piping systems. It is here applied to the Residual Heat Removal (RHR) bypass system. A large Eddy Simulation (L.E.S.) approach is used to model the turbulent flow in a T-junction. The thermal coupling between the Finite Volume CFD Code_Saturne and the Finite Element thermal code Syrthes, gives access to the instantaneous field inside the fluid and the solid. By using the instantaneous solid thermal fields, mechanical computations (as presented in (Stephan et al 2002)) are performed to yield the instantaneous mechanical stresses seen by the pipework T-junction and elbow.
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Leclercq, Christophe, Regiane Fortes-Patella, Antoine Archer, and Fabien Cerru. "First Attempt on Numerical Prediction of Cavitation Damage on a Centrifugal Pump." In ASME 2017 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/fedsm2017-69085.
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The cavitation erosion remains an industrial issue for many applications, mainly for hydraulic machines. This paper deals with the cavitation intensity, which can be described as the fluid mechanical loading causing cavitation damage. The estimation of this intensity is a challenging problem both in terms of modeling the cavitating flow and predicting the erosion due to cavitation. For this purpose, a numerical methodology was proposed to estimate cavitation intensity from 3D unsteady cavitating flow simulations. CFD calculations were carried out using Code_Saturne, which solves U-RANS equations for a homogeneous fluid using the Merkle’s model [1], coupled to a k-ε turbulence model with the Reboud’s correction. A cavitation intensity prediction model was developped based on pressure and void fraction derivatives obtained through CFD calculations. It was previously applied to study cavitation damage [2] on a NACA65012 hydrofoil. The article briefly presents this validation case as well as the prediction of the cavitation intensity on the blades of a centrifugal pump called “SHF pump” and tested at EDF R&D laboratory [3]. The numerical predictions of cavitation damage are in good agreement with experimental results obtained by pitting.
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Li, Jingya, and Xiaoying Zhang. "CFD Simulation of Passive Containment Cooling System in Hot Leg SB-LOCA for 1000MW PWR." In 2017 25th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/icone25-66025.
Abstract:
The passive cooling system (PCCS) for reactor containment is a security system that can be used to cool the atmosphere and reduce pressure inside of containment in case of temperature and pressure increase caused by vapor injection, which requires no external power because it works only with natural forces. However, as the driving forces from natural physical phenomena are of low amplitude, uncertainties and instabilities in the physical process can cause failure of the system. This article aims to establish a CFD simulation model for the Passive Containment Cooling System of 1000MW PWR using Code_Saturne and FLUENT software. The comparison of 4 different models based respectively on mixture model, COPAIN test, Uchida correlation and Chilton-Colburn analogy which simulate the condensing effect and the improvement of source code are based on a 3D simulation of PCCS system. To simulate the thermal-hydraulic condition in the containment after LOCA accident caused by a double-ended main pipe rupture, a high temperature vapor with the given mass flow rate are supposed to be the source of energy and mass into containment. Meanwhile the surface of three condensing island applies the wall condensation model. The simulation results show similar transient process obtained with the 4 models, while the difference between the transient simulation and the steady-state analysis of three models is less than 3%. The large mass flow rate of water loss status inside the containment cause a high flow rate of vapor which could be uniformly mixed with air in a short time. For the self-condensing efficiency of 3 groups of PCCS system, the non-centrosymmetric injection position resulting that the condensing efficiency is slightly higher for the two heat exchanger groups nearby. During the first 2400s of simulation time, more than 75.69% of the vapor is condensed, indicating that for the occurrence of condensation at the wall mainly driven by natural convection, the effect of thermodynamic siphon could improve the flow of gas mixture inside the tubes when the velocity of mixture is not large enough, so that the vapor could smoothly enter the tube and reach the internal cooling surface then to be condensed. Besides, PCCS ensure the containment internal pressure maintained below 2 bar and the temperature maintained below 380K during 3600s.
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Bichet, Th, A. Martin, and F. Beaud. "Fluid Flow Separation in Down Comer During a Safety Injection Scenario: Quantitative Experimental Results." In ASME 2004 Heat Transfer/Fluids Engineering Summer Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ht-fed2004-56029.
Abstract:
Within the framework of the nuclear power plant lifetime issue, the assessment of the French 900 MWe (3-loops) series Reactor Pressure Vessel (RPV) integrity was performed. A simplified analysis has shown that one of the most severe loading condition is given by the small break loss of coolant accidents (SBLOCA) due to the pressurized injection of cold water (9°C) into the cold leg and down comer of the RPV. Two main physical phenomena, considered important for the RPV cooling transient, were identified during numerical application obtained with EDF CFD tools. These phenomena are the fluid flow separation and the plume oscillations in the down comer. In order to consolidate these numerical results with the EDF home code, called Code_Saturne, an experimental study has been carried out with the new EDF R&D facility. This transparent experimental model is based on the representation at 1/2 scale of a cold leg and a third of down comer including a thermal shield. The experiments were realized by injecting of salt water flow (density effects) in the cold leg according to a similitude study based on Froude number conservation between experiments and reactor scenarios. Firstly, this paper presents the main qualitative experimental results, based essentially on visualizations of different injections of dyed salt water in the cold leg and in the down comer. The physical phenomena observed showed a qualitative good agreement between visualizations and numerical results. Secondly, this paper presents the first experimental results of the assessment of the fluid flow separation in the experimental model obtained with temperature probes inserted in the down comer. We showed, in the experiments analysis, the fluid flow separation and the jet oscillations were detected. The next step will consist to compare these quantitative experiments with numerical study which will be carry out with Code_Saturne.
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Martin, A., S. Benhamadouche, G. Bezdikian, F. Beaud, and F. Lestang. "CFD-Tool for Assessment of the Reactor Pressure Vessel Integrity in Pressure Thermal Shock Conditions: Influence of Turbulence Model and Mesh Refinement on the Vessel Thermal Loading During PTS Transient." In ASME 2006 Pressure Vessels and Piping/ICPVT-11 Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/pvp2006-icpvt-11-93311.
Abstract:
Integrity evaluation methods for nuclear Reactor Pressure Vessels (RPVs) under Pressurised Thermal Shock (PTS) loading are applied by French Utility. They are based on the analysis of the behavior of relatively shallow cracks under loading PTS conditions due to the emergency cooling during SBLOCA (Small Break Loss of Coolant Accident) transients. This paper presents the Research and Development program started at E.D.F on the Computational Fluid Dynamic (CFD) determination of the cooling phenomena of a PWR vessel during a Pressurised Thermal Shock. The numerical results are obtained with the thermal-hydraulic tool Code_Saturne, in combination with the thermal-solid code SYRTHES to take into account the coupled effect of heat transfer between the fluid flow and the vessel. Based on the global and local Thermal-hydraulic analysis of a Small Break Loss of Coolant Accident transient, the paper presents mainly a parametric study which helps to understand the main phenomena that can lead to better estimating the margin factors. The geometry studied represents a third of a PWR pressure vessel and the configuration investigated is related to the injection of cold water in the vessel during a SBLOCA transient. Conservative initial and boundary conditions for the CFD calculation are derived from the global Thermal-hydraulic analysis. Both the fluid behavior and its impact on the solid part formed by cladding and base metal are considered. The main purpose of the numerical thermal-hydraulic studies is to accurately estimate the distribution of fluid temperature in the down comer and the heat transfer coefficients on the inner RPV surface for a fracture mechanics computation which will subsequently assess the associated RPV safety margin factors.
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Peyrard, Christophe, Marco Belloli, Pierre Bousseau, Sara Muggiasca, Stefano Giappino, Richard Howard, and Daniele Rocchi. "CFD Modeling of Flow Induced Vibration on a Mobile Cylinder for a 30 K-60 K Reynolds Number Comparison Between Simulation and Experimental Results." In ASME 2009 Pressure Vessels and Piping Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/pvp2009-77534.
Abstract:
Fatigue and aging of electrical overhead transmission lines is a major concern nowadays in developed countries with ever increasing difficulties to build new lines and an already quite aged network. An important degradation phenomenon of overhead line cables is fretting fatigue close to the suspension clamps due to vortex induced vibrations (VIV). These VIV are generally observed for wind speeds in the range of 1 to 7 m/s. The existing industrial practice for predicting how prone cables are to VIV fatigue is based on a balance between the power generated by the wind and the power dissipated by the cable system. The power generated by the wind has been evaluated through measurements on real line spans and through wind tunnel experiments on rigid and flexible cylinders as a function of frequency and vibration amplitude. The wind tunnel measurement results are mainly performed for constant flow speed. Corresponding results show a scattering from simple to double. Furthermore, complementary investigations are required to better evaluate the power with wind speed variations across and along the overhead line span. EDF R&D (with Code_Saturne open source software) and Politecnico di Milano have evaluated CFD modeling on a mobile rigid cylinder with comparison to detailed wind tunnel measurement results performed by Politecnico di Milano on a 20 cm diameter rigid cylinder equipped with a pressure scanner. This paper presents the steps, the different questions raised, the difficulties and limitations for the setting and the realization of the CFD modeling approach. The comparison between experimental results and simulation results is presented for the mobile rigid cylinder with k-ω SST turbulence model.