30 research outputs found
Simulations CFD hybrides d'écoulements diphasiques dans un séparateur d'écoulement en ligne
No full textInline fluid separation using a swirl element is a recent technology for oil/gas extraction. The static swirl element, installed inside the pipeline, is able to transform part of the arriving axial momentum into an azimuthal momentum when the flow goes through its blades. This produces centrifugal forces up to 100 times the gravitational acceleration separating then the phases based on their densities, the heavy phase is pushed next to the wall and the light one to the centre to be recovered at the outlet of the separator by a pick-up tube. The current study is part of a European project TOMOCON aims at developing CFD methods in the IMFT inhouse code JADIM to simulate the two phase flow separation. Since the scales are ranging from 1 m the length of the device (pipe, swirl element) to 1 mm which is the size of the smallest bubbles and drops, the numerical strategy needs to combine Eulerian and Lagrangian schemes. First, taking into account the complexity of the geometry, the pipe, the swirl element and the pick-up tube are simulated using Immersed Boundary Method (IBM) for solid/fluid interaction on a regular Cartesian mesh. The flow being highly turbulent that Direct Numerical Simulation (DNS) is not possible, Large Eddy Simulation (LES) is considered and the turbulence is modeled using mixed dynamic Smagorinsky model. Then the Lagrangian solver is used to track the dispersed phase (droplets/bubbles). Once the separation is done and the bubbles/droplets accumulation takes place leading to large volume of gas/oil compared to the mesh size, we switch to the Volume of Fluid (VoF) method to simulate the core inside the heavy phase. Hybrid models to combine LES/IBM, IBM/Lagrangian tracking et Lagrangian tracking/VoF are proposed and validated to enable the simulation of the inline fluid separation process. The numerical results help to fix the physical parameters influencing the separation and controlling the efficiency and validate models with experimental data from TU Delft, HZDR and TUL.La séparation en ligne des écoulements diphasiques est une nouvelle technologie qui commence à intéresser les industries pétrolières grâce aux avantages qu'elle présente. Lé séparateur est composé d'un obstacle installé à l'intérieur du pipeline et muni d'ailettes mettant en rotation l'écoulement ce qui produit une force centrifuge jusqu'à 100 fois l'accélération gravitationnelle et permettant de séparer deux phases en se basant sur la différence entre leurs densités. La phase lourde est poussée vers la paroi du pipeline et la phase légère reste au centre pour etre récuperée par la suite à la sortie du séparateur par un tube collecteur. Ce sujet de thèse , qui s'inscrit dans le cadre d'un projet européen TOMOCON, a pour objectif de simuler numériquement ce processus de séparation en utilisant le code CFD JADIM développé au sein de l'IMFT. Étant donné que le rapport entre l'échelle du dispositif de séparation et celle de la bulle/goutte à récupérer est de l'ordre de 1000, une méthode numérique hybride combinant à la fois un schéma Eulerien et un autre Lagrangien s'avère la solution numérique adéquate à un tel problème. Tout d'abord, compte tenu de la complexité de la géometrie du séparateur, Immersed Boundary Method (IBM) est utilisé pour résoudre l'interaction fluide/structure et simuler les parties solides du séparateur sans avoir recours à un maillage complexe, le modèle dynamique mixte de Smagorinsky du solver Large Eddy Simulation (LES) est utilisé pour la modélisation de la turbulence vu que l'écoulement est fortement tubulent. Le solver Lagrangien permet le suivi de la phase dispersée jusqu'à ce que l'accumulation des bulles/gouttes après séparation ait lieu, et c'est ainsi qu'on commute à la méthode Volume of Fluid (VoF) pour présenter les deux phases et simuler le coeur formé. Et pour assurer une bonne interaction entre ces diverses méthodes CFD, des modèles hybrides sont proposées pour LES/IBM, IBM/Lagrangian tracking et Lagrangian tracking/VoF permettant ainsi la simulation du processus de séparation avec un cout CPU raisonable. Les paramètres physiques contrôlant la séparation sont ensuite conclus à partir des simulations numériques et des comparaisons sont faites avec les résultats expérimentaux issus de TU Delft, HZDR et de TUL
Simulations CFD hybrides d'écoulements diphasiques dans un séparateur d'écoulement en ligne
No full textLa séparation en ligne des écoulements diphasiques est une nouvelle technologie qui commence à intéresser les industries pétrolières grâce aux avantages qu'elle présente. Lé séparateur est composé d'un obstacle installé à l'intérieur du pipeline et muni d'ailettes mettant en rotation l'écoulement ce qui produit une force centrifuge jusqu'à 100 fois l'accélération gravitationnelle et permettant de séparer deux phases en se basant sur la différence entre leurs densités. La phase lourde est poussée vers la paroi du pipeline et la phase légère reste au centre pour etre récuperée par la suite à la sortie du séparateur par un tube collecteur. Ce sujet de thèse , qui s'inscrit dans le cadre d'un projet européen TOMOCON, a pour objectif de simuler numériquement ce processus de séparation en utilisant le code CFD JADIM développé au sein de l'IMFT. Étant donné que le rapport entre l'échelle du dispositif de séparation et celle de la bulle/goutte à récupérer est de l'ordre de 1000, une méthode numérique hybride combinant à la fois un schéma Eulerien et un autre Lagrangien s'avère la solution numérique adéquate à un tel problème. Tout d'abord, compte tenu de la complexité de la géometrie du séparateur, Immersed Boundary Method (IBM) est utilisé pour résoudre l'interaction fluide/structure et simuler les parties solides du séparateur sans avoir recours à un maillage complexe, le modèle dynamique mixte de Smagorinsky du solver Large Eddy Simulation (LES) est utilisé pour la modélisation de la turbulence vu que l'écoulement est fortement tubulent. Le solver Lagrangien permet le suivi de la phase dispersée jusqu'à ce que l'accumulation des bulles/gouttes après séparation ait lieu, et c'est ainsi qu'on commute à la méthode Volume of Fluid (VoF) pour présenter les deux phases et simuler le coeur formé. Et pour assurer une bonne interaction entre ces diverses méthodes CFD, des modèles hybrides sont proposées pour LES/IBM, IBM/Lagrangian tracking et Lagrangian tracking/VoF permettant ainsi la simulation du processus de séparation avec un cout CPU raisonable. Les paramètres physiques contrôlant la séparation sont ensuite conclus à partir des simulations numériques et des comparaisons sont faites avec les résultats expérimentaux issus de TU Delft, HZDR et de TUL.Inline fluid separation using a swirl element is a recent technology for oil/gas extraction. The static swirl element, installed inside the pipeline, is able to transform part of the arriving axial momentum into an azimuthal momentum when the flow goes through its blades. This produces centrifugal forces up to 100 times the gravitational acceleration separating then the phases based on their densities, the heavy phase is pushed next to the wall and the light one to the centre to be recovered at the outlet of the separator by a pick-up tube. The current study is part of a European project TOMOCON aims at developing CFD methods in the IMFT inhouse code JADIM to simulate the two phase flow separation. Since the scales are ranging from 1 m the length of the device (pipe, swirl element) to 1 mm which is the size of the smallest bubbles and drops, the numerical strategy needs to combine Eulerian and Lagrangian schemes. First, taking into account the complexity of the geometry, the pipe, the swirl element and the pick-up tube are simulated using Immersed Boundary Method (IBM) for solid/fluid interaction on a regular Cartesian mesh. The flow being highly turbulent that Direct Numerical Simulation (DNS) is not possible, Large Eddy Simulation (LES) is considered and the turbulence is modeled using mixed dynamic Smagorinsky model. Then the Lagrangian solver is used to track the dispersed phase (droplets/bubbles). Once the separation is done and the bubbles/droplets accumulation takes place leading to large volume of gas/oil compared to the mesh size, we switch to the Volume of Fluid (VoF) method to simulate the core inside the heavy phase. Hybrid models to combine LES/IBM, IBM/Lagrangian tracking et Lagrangian tracking/VoF are proposed and validated to enable the simulation of the inline fluid separation process. The numerical results help to fix the physical parameters influencing the separation and controlling the efficiency and validate models with experimental data from TU Delft, HZDR and TUL
Hybrid CFD simulations of two-phase flows in inline flow splitters
No full textInline fluid separation using a swirl element is a recent technology for oil/gas extraction. The static swirl element, installed inside the pipeline, is able to transform part of the arriving axial momentum into an azimuthal momentum when the flow goes through its blades. This produces centrifugal forces up to 100 times the gravitational acceleration separating then the phases based on their densities, the heavy phase is pushed next to the wall and the light one to the centre to be recovered at the outlet of the separator by a pick-up tube. The current study is part of a European project TOMOCON aims at developing CFD methods in the IMFT inhouse code JADIM to simulate the two phase flow separation. Since the scales are ranging from 1 m the length of the device (pipe, swirl element) to 1 mm which is the size of the smallest bubbles and drops, the numerical strategy needs to combine Eulerian and Lagrangian schemes. First, taking into account the complexity of the geometry, the pipe, the swirl element and the pick-up tube are simulated using Immersed Boundary Method (IBM) for solid/fluid interaction on a regular Cartesian mesh. The flow being highly turbulent that Direct Numerical Simulation (DNS) is not possible, Large Eddy Simulation (LES) is considered and the turbulence is modeled using mixed dynamic Smagorinsky model. Then the Lagrangian solver is used to track the dispersed phase (droplets/bubbles). Once the separation is done and the bubbles/droplets accumulation takes place leading to large volume of gas/oil compared to the mesh size, we switch to the Volume of Fluid (VoF) method to simulate the core inside the heavy phase. Hybrid models to combine LES/IBM, IBM/Lagrangian tracking et Lagrangian tracking/VoF are proposed and validated to enable the simulation of the inline fluid separation process. The numerical results help to fix the physical parameters influencing the separation and controlling the efficiency and validate models with experimental data from TU Delft, HZDR and TUL
Intra-hour Forecasting of Direct Normal Solar Irradiance Using Variable Selection with Artificial Neural Networks
No full textStochastic wall model for turbulent pipe flow using Immersed Boundary Method and Large Eddy Simulation
No full textInternational audienceA hybrid IBM-LES method is presented with the objective to simulate high-Reynolds number pipe flows on coarse Cartesian meshes. The IBM method is first used to simulate a laminar pipe flow and results have shown to converge with second order accuracy to the exact solution. A new forcing scheme inside the IBM wall thickness improves significantly numerical accuracy and provides an interesting way to control the fluid–solid interaction. Based on this new modeling of the IBM wall boundary condition, turbulent pipe flows for Reynolds numbers in the range 50,000 to 500,000 are then considered. The IBM wall forcing under these conditions is developed based on the classical turbulent wall laws, namely the log-law and the power-law, able to reproduce the mean velocity profile. We show that adjusting the control parameters of these two models makes possible to recover the correct bulk velocity and mean velocity profile. In order to improve the fluctuations level and spatial distribution of turbulent structures inside the pipe, we propose to extend the log-law modeling using local and unsteady value of the wall shear stress obtained from a stochastic model. The latter preserves spatiotemporal correlations of the wall friction and enhances the reliability of the simulations in terms of both mean bulk flow and fluctuations. The effects of both the Reynolds number and the grid resolution are also discussed and empiric correlations for the model parameters are proposed
CFD APPROACH TO SIMULATE TWO PHASE FLOW INLINE-SEPARATOR COUPLING IBM, LES, LAGRANGIAN TRACKING AND VOF METHODS
No full textx Inline fluid separation using a swirl element is a recent technology for oil/gas processing. Centrifugal forces up to 100 times the gravitational acceleration separate the phases, leaving the heavy phase close to the wall and the light one in the center. The current study is part of a Europeen project TOMOCON aiming at developing CFD methods in the in-house code JADIM to simulate the two-phase flow separation in order to help the development of inline separation control. The objective is to propose a hybrid approach based on Navier Stokes solver that makes possible accurate simulations with coarse spatial resolution. First, Immersed Boundary Method (IBM) is used to simulate both the pipe and the complex geometry of the swirl element on a cartesian regular mesh. Turbulence is modeled by the classical dynamic Smagorinsky sub-grid model in Large Eddy Simulation (LES) with a special stochastic wall law coupled to the IBM allowing to avoid the need for a mesh refinement in the near wall region. A Lagrangian tracking (LT) method is used to solve the dispersed bubbly flow and it is coupled to the Volume of Fluid (VoF) approach once the coalescence takes place and the gas core is formed. The numerical strategy based on the coupling of these different methods is presented and we report some of the simulations used for the verification-validation of the numerical developments
Patriarchy, Gender Discrimination and Resistance in Buchi Emecheta’s Second Class Citizen (1974) and Kehinde (1994)
No full text30cm ; 50p.As one of the most figures of the Nigerian Literature, Buchi Emecheta displays a vivid portrayal of the bitter realities of certain patriarchal practices in the African culture, which not only thwarted Black women but also hampered them from having a position in the society. This study selected two of her novels, Second Class Citizen (1974) and Kehinde (1994). It discusses issues of patriarchy, gender discrimination and Resistance in both novels. This thesis is based on Alice Walker’s Womanism, developed in her collection of essays In Search Of Our Mothers Garden: Womanist Prose (1983). In this analysis we have tried to show that despite the fact that the two works are twenty years apart, the author is still discusses the same issues that come from her cultural and personal experiences. The author has portrayed the oppression practiced towards women. She has depicted how women are dominated by men in patriarchal societies. Emecheta has also described how these women rebel and seek for independence through the process of education. This study concludes that Emecheta succeeds in using resistant and powerful female character, aiming at identifying the suffering of women as she underlines a strong autobiographical quality of writing her novels. As well as, women as a subject of oppression are always seeking for freedom
Controlled Inline Fluid Separation Based on Smart Process Tomography Sensors
No full textToday's mechanical fluid separators in industry are mostly operated without any control to maintain efficient separation for varying inlet conditions. Controlling inline fluid separators, on the other hand, is challenging since the process is very fast and measurements in the multiphase stream are difficult as conventional sensors typically fail here. With recent improvement of process tomography sensors and increased processing power of smart computers, such sensors can now be potentially used in inline fluid separation. Concepts for tomography-controlled inline fluid separation were developed, comprising electrical tomography and wire-mesh sensors, fast and massive data processing and appropriate process control strategy. Solutions and ideas presented in this paper base on process models derived from theoretical investigation, numerical simulations and analysis of experimental data.ChemE/Transport Phenomen
Towards Tomography-Based Real-Time Control of Multiphase Flows: A Proof of Concept in Inline Fluid Separation
No full textThe performance of multiphase flow processes is often determined by the distribution of phases inside the equipment. However, controllers in the field are typically implemented based on flow variables, which are simpler to measure, but indirectly connected to performance (e.g., pressure). Tomography has been used in the study of the distribution of phases of multiphase flows for decades, but only recently, the temporal resolution of the technique was sufficient for real-time reconstructions of the flow. Due to the strong connection between the performance and distribution of phases, it is expected that the introduction of tomography to the real-time control of multiphase flows will lead to substantial improvements in the system performance in relation to the current controllers in the field. This paper uses a gas–liquid inline swirl separator to analyze the possibilities and limitations of tomography-based real-time control of multiphase flow processes. Experiments were performed in the separator using a wire-mesh sensor (WMS) and a high-speed camera to show that multiphase flows have two components in their dynamics: one intrinsic to its nonlinear physics, occurring independent of external process disturbances, and one due to process disturbances (e.g., changes in the flow rates of the installation). Moreover, it is shown that the intrinsic dynamics propagate from upstream to inside the separator and can be used in predictive and feedforward control strategies. In addition to the WMS experiments, a proportional–integral feedback controller based on electrical resistance tomography (ERT) was implemented in the separator, with successful results in relation to the control of the distribution of phases and impact on the performance of the process: the capture of gas was increased from 76% to 93% of the total gas with the tomography-based controller. The results obtained with the inline swirl separator are extended in the perspective of the tomography-based control of quasi-1D multiphase flows
RECONNEXION WITH NATURE AND SOLIDARITY, TWO MAJOR KEYS IN THE FIGHT AGAINST CLIMATE CATACLYSM IN C’EST LE MONDE A L’ENVERS BY NICOLAS VANIER
No full textThis study invites us to reflect on our modern lives where the dramatic consequences of global warming are manifesting on a planetary scale: droughts and famines, massive migrations, oil shortages and soaring prices, economic crises and conflicts, etc. . In this novel, the author pushes us to question the absurdity of our production, our dependence on the economy and our mode of consumption. It nevertheless highlights the moral values which make us capable of reaching a livable future. The story takes place at a time when all the social, climate, ecological and migrant crises that were brewing for years suddenly appear conjugate. In short, this is the great collapse. Severe heatwaves are hitting France and making daily life increasingly difficult. The resulting national power outage and fuel shortage are throwing the lives of millions of people into chaos. Among them, a wealthy couple, Stanislas and Sophie and their “eco-friendly” son Jonathan, living in Paris, will undertake a perilous journey by bike to reach the Morvan, where Stanislas had bought a farm some time earlier. When the family arrived at the farm, Patrick, the farmer, refuses to give the land to the Parisians because he did not benefit from the money received from the sale, having no longer any value. However, the two families end up learning to live together with the resources that nature offers them and thus defining the terms of a new lifestyle. This story could come out as anxiety-provoking, the author nevertheless shows confidence in human beings, believing in solidarity and resilience and adaptation. He finally calls for a reconnection between human beings and nature
