Academic literature on the topic 'VOF simulations'
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Journal articles on the topic "VOF simulations"
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Lubin, Pierre, and Stéphane Glockner. "NUMERICAL SIMULATIONS OF BREAKING SOLITARY WAVES." Coastal Engineering Proceedings 1, no. 33 (September 28, 2012): 59. http://dx.doi.org/10.9753/icce.v33.waves.59.
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This paper presents the application of a parallel numerical code to breaking solitary waves impacting a seawall structure. The three-dimensional Navier-Stokes equations are solved in air and water, coupled with a subgrid-scale model to take turbulence into account. We compared three numerical methods for the free-surface description, using the classical VOF-PLIC and VOF-TVD methods, and an original VOF-SM method recently developed in our numerical tool (Vincent et al., 2010). Some experimental data for solitary waves impinging and overtopping coastal structures are available in literature (Hsiao et al., 2010). Solitary waves are often used to model tsunami behaviors because of their hydrodynamic similarities. From a numerical point of view, it allows shorter CPU time simulations, as only one wave breaks. Here we apply the model to simulate three-dimensional solitary waves and compare qualitatively our results with the experimental data. We investigate three configurations of solitary waves impinging and overtopping an impermeable seawall on a 1:20 sloping beach.
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Yahyaee, Ali, Amir Sajjad Bahman, Klaus Olesen, and Henrik Sørensen. "Level-Set Interface Description Approach for Thermal Phase Change of Nanofluids." Nanomaterials 12, no. 13 (June 29, 2022): 2228. http://dx.doi.org/10.3390/nano12132228.
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Simulations of thermally driven phase change phenomena of nanofluids are still in their infancy. Locating the gas–liquid interface location as precisely as possible is one of the primary problems in simulating such flows. The VOF method is the most applied interface description method in commercial and open-source CFD software to simulate nanofluids’ thermal phase change. Using the VOF method directs to inaccurate curvature calculation, which drives artificial flows (numerical non-physical velocities), especially in the vicinity of the gas–liquid interface. To recover accuracy in simulation results by VOF, a solver coupling VOF with the level-set interface description method can be used, in which the VOF is employed to capture the interface since it is a mass conserving method and the level-set is employed to calculate the curvature and physical quantities near the interface. We implemented the aforementioned coupled level-set and VOF (CLSVOF) method within the open-source OpenFOAM® framework and conducted a comparative analysis between CLSVOF and VOF (the default interface capturing method) to demonstrate the CLSVOF method’s advantages and disadvantages in various phase change scenarios. Using experimental mathematical correlations from the literature, we consider the effect of nanoparticles on the base fluid. Results shows that the new inferred technique provides more precise curvature calculation and greater agreement between simulated and analytical/benchmark solutions, but at the expense of processing time.
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Shang, Zhi, Jing Lou, and Hongying Li. "Simulations of Flow Transitions in a Vertical Pipe Using Coupled Level Set and VOF Method." International Journal of Computational Methods 14, no. 02 (February 22, 2017): 1750013. http://dx.doi.org/10.1142/s021987621750013x.
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The level set (LS) and volume-of-fluid (VOF) methods are usually employed to simulate the two-phase flow. However every single method of them will face the mass conservative or accurate issues during the simulation. The coupled level set and volume-of-fluid (CLSVOF) method was not only able to conquer the shortages of the LS and VOF methods but also simultaneously keep the merits of both of the methods. In CLSVOF method the geometry reconstruction technology was employed to realize the coupling between LS and VOF. After the validation of single bubble rising cases, the CLSVOF method was used to simulate the complex transitional two-phase flows in a vertical pipe and the simulation results were compared to experiments.
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Spitzenberger, Andy, Sebastian Neumann, Martin Heinrich, and Rüdiger Schwarze. "Particle detection in VOF-simulations with OpenFOAM." SoftwareX 11 (January 2020): 100382. http://dx.doi.org/10.1016/j.softx.2019.100382.
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Yu, Qun, Xiao Dong Hu, Long Huan Huang, and Yue Lin. "Optimum Design and Analysis of Metal Delivery System for Magnesium Alloy Plates with Twin-Roll Casting Process." Applied Mechanics and Materials 395-396 (September 2013): 1150–53. http://dx.doi.org/10.4028/www.scientific.net/amm.395-396.1150.
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Using physical and numerical simulation method，metal delivery system of twin-roll casting magnesium alloy process was researched. The Anycasting software was used to simulate different flow systems by VOF method. And based on similar principles, an acrylic experimental model with the ratio of 1:1 was designed. The dam’s size and position were optimized by simulations and experiments. The flow distribution is uniform along the horizontal of the casting roller. Numerical simulation and physical simulation are in good coincidence.
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Sato, Kenta, and Shunichi Koshimura. "A LATTICE BOLTZMANN APPROACH FOR THREE-DIMENSIONAL TSUNAMI SIMULATION BASED ON THE PLIC-VOF METHOD." Coastal Engineering Proceedings, no. 36 (December 30, 2018): 90. http://dx.doi.org/10.9753/icce.v36.papers.90.
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Free surface flow problems occur in numerous disaster simulations, such as tsunamis inland penetration in urban area. Simulation models for these problems have to be non-hydrostatic and three-dimensional because of the strong non-linearity and higher-order physical phenomena. Despite all the progress in the modern computational fluid dynamics, such simulations still present formidable challenges both from numerical and computational cost point of view. The lattice Boltzmann method (LBM) has been attracting attention as an alternative fluid simulation tool to overcome the problems. In current study, LBM for three-dimensional tsunami simulations is developed which are coupled with the piecewise linear interface calculation with the Volume of Fluid (VOF) approach. This model is for an efficient three-dimensional tsunami simulation by a one-fluid formulation, where the lattice Boltzmann equation is assigned to solve for a single virtual fluid. Various benchmark problems are also carried out to validate the utility of the proposed models in term of coastal engineering.
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Wu, Zhi-Yong, Wei-Hua Cai, Guo-Dong Qiu, and Yi-Qiang Jiang. "Prediction of Mass Transfer Time Relaxation Parameter for Boiling Simulation on the Shell-Side of LNG Spiral Wound Heat Exchanger." Advances in Mechanical Engineering 6 (January 1, 2014): 275708. http://dx.doi.org/10.1155/2014/275708.
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The objective of this present study is to propose an approach to predict mass transfer time relaxation parameter for boiling simulation on the shell-side of LNG spiral wound heat exchanger (SWHE). The numerical model for the shell-side of LNG SWHE was established. For propane and ethane, a predicted value of mass transfer time relaxation parameter was presented through the equivalent evaporation simulations and was validated by the Chisholm void fraction correlation recommended under various testing conditions. In addition, heat transfer deviations between simulations using the predicted value of mass transfer time relaxation parameter and experiments from Aunan were investigated. The boiling characteristics of SWHE shell-side were also visualized based on the simulations with VOF model. The method of predicting mass transfer time relaxation parameter may be well applicable to various phase change simulations.
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NAKAJIMA, Ryota, Takumi CHIBA, Hirokazu UMEMIYA, Sumihisa ODA, and Shunji HOMMA. "Numerical Simulations for Curtain Coating by VOF Method." JAPANESE JOURNAL OF MULTIPHASE FLOW 33, no. 4 (November 7, 2019): 417–23. http://dx.doi.org/10.3811/jjmf.2019.013.
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Kranjčević, Lado, Luka Grbčić, Matija Mrazović, and Siniša Družeta. "Rijeka Bay 3D VOF Costal Flow Model." Journal of Maritime & Transportation Science 3, no. 3 (June 2020): 125–32. http://dx.doi.org/10.18048/2020.00.09.
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3D multiphase flow was analyzed in the area of Rijeka bay in the Adriatic Sea. The necessary morphology data in the range of interest of the coastal bottom area were collected and the spatial surface was created. The functionality of the 3D model was studied in the large area of the realistic stochastic structure of the bottom and the shore. The probability of meteorological conditions and wind impact in the model has been shown. The obtained results give a detailed view of the velocity fields in the horizontal plane of different depths. Numerical simulation was performed in open source program OpenFOAM with Volume of Fluid (VOF) method using the Eulerian approach. For solving this problem interFOAM solver for two incompressible, isothermal, immiscible fluids was used. The resulting simulations showed dominant flow from the western coast of the Krk island to the eastern coast of the Istrian peninsula. Seawater enters the bay through the Srednja Vrata and Tihi Kanal and exits the bay through the Vela Vrata. This research has shown that using a VOF method can be successfully implemented for describing fluid motion in large areas such as bays and oceans.
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Taamneh, Yazan. "Influence of Jordanian zeolite on the performance of a solar still: experiments and CFD simulation studies." Water Supply 16, no. 6 (June 2, 2016): 1700–1709. http://dx.doi.org/10.2166/ws.2016.091.
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Computational fluid dynamics (CFD) simulations were performed for experiments carried out with two identical pyramid-shaped solar stills. One was filled with Jordanian zeolite-seawater and the second was filled with seawater only. This work is focused on CFD analysis validation with experimental data conducted using a model of phase change interaction (evaporation-condensation model) inside the solar still. A volume-of-fluid (VOF) model was used to simulate the inter phase change through evaporation-condensation between zeolite-water and water vapor inside the two solar stills. The effect of the volume fraction of the zeolite particles (0 ≤ ϕ ≤ 0.05) on the heat and distillate yield inside the solar still was investigated. Based on the CFD simulation results, the hourly quantity of freshwater showed a good agreement with the corresponding experimental data. The present study has established the utility of using the VOF two phase flow model to provide a reasonable solution to the complicated inter phase mass transfer in a solar still.
Dissertations / Theses on the topic "VOF simulations"
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Drumright-Clarke, Mary Ann. "Numerical simulations that characterize the effects of surfactant on droplets in shear flow." Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/26895.
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Numerical simulations utilizing the code SURFER++ with the incorporation of an insoluble surfactant in the VOF scheme were conducted to characterize the effects of surfactant on a drop in shear flow. The drop is suspended in a matrix liquid. A parameter called reduction, which specifically relates to a percentage decrease in effective surface tension, is used to measure the surfactant amount on the interface. In a model system where reduction = 0.1, viscosity ratio = 1 and density ratio = 1, it was found that stable drops tend to be more elongated and less inclined to the primary flow direction than drops unexposed to surfactant. This can be explained by the location of surfactant at the interface as the drop evolves. Breaking drops also show a flattened angle, but exhibit shorter necks and faster time to break than similar drops without surfactant. As reduction increases, various physical characteristics of the drops change across Reynolds number.Ph. D.
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Fanzar, Abdelaziz. "Développement d’un code numérique pour la simulation et l’étude de l’hydrodynamique et de la physico-chimie de milieux diphasiques incompressibles. Cas d’une goutte d’eau dans l’huile de paraffine." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4339.
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Depuis plusieurs décennies, une importante activité scientifique se concentre sur la description numérique, théorique ou expérimentale de l'hydrodynamique des écoulements multiphasiques. Ces écoulements sont caractérisés par l'existence d'interfaces, et d'une force à l'interface, la tension superficielle, séparant généralement deux fluides non miscibles. Un cas d'étude dans ce contexte est le problème du drainage d'une unique goutte dans une phase continue, l'ensemble étant soumis à la gravité. Ce système fait apparaître des écoulements récemment décrits pour une goutte d'eau dans l'huile de paraffine. Ce système constitue également un modèle simple pour l'étude des propriétés aux interfaces, Mais d'un point de vue numérique, se pose alors le problème de la stabilité des algorithmes pouvant être utilisés. Les effets aux interfaces impliquent en effet des domaines spatiaux très limités dans lesquels les grandeurs physiques entre les deux fluides sont discontinues. D'importants artéfacts numériques peuvent alors être générés dans les simulations et faire perdre la richesse de la physico-chimie du système considéré. Le problème de la simulation d'écoulements multiphasiques intéresse aussi bien le monde académique que le monde industriel. L'objectif de ce travail de thèse est donc d'implémenter les techniques numériques les plus récentes et de développer un code pour permettre la simulation de l'hydrodynamique de systèmes dispersés. Pour parvenir à ce but, il reste encore des problèmes algorithmiques importants à résoudre comme la prise en compte des effets thermocapillaires et thermosolutaux. Ces deux derniers points sont l'objet de cette thèseFor several decades, an important scientific activity has focused on the numerical, theoretical and experimental hydrodynamics of drops. This work presents numerical results of a single droplet in the gravity field and in non-isothermal conditions. The simulation such a multiphase system is important in both academic and industrial world. This is particularly the case in the field of emulsions, wetting problems and evaporation. To achieve this goal, there are still important algorithmic problems due to the free moving interfaces and the description of capillary effects. Here, a Volume of Fluid technique has been implemented with high order temporal and spatial schemes to preserve the sharpness of the drop interface. The system under consideration is a simplified model consisting in a single water droplet in a continuous paraffin oil phase. These liquids are immiscible and non-compressible and the overall evolution is unsteady. Capillary contributions such as temperature and surfactant dependent surface tension are fully accounted for. This presentation is aimed to show the capabilities of VOF techniques for the simulations of unsteady multiphase systems in non-isothermal configurations. The role of the droplet initial position and temperature field is described with good numerical stability. There are still important problems remaining in the simulation of free interface systems with such a technique. Spurious currents induced by the description of capillarity can in particular come into play. But these latter can be controlled once the droplet average velocity due to drainage becomes large enough
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Oruganti, Surya Kaundinya. "Stochastic models on residual scales in LES of sprays in diesel-like conditions : spray formation, turbulent dispersion and evaporation of droplets." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEC042.
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Dans le cadre de la simulation à grandes échelles (LES), la thèse aborde la simulation des sprays dans les conditions d’un moteur à injection directe. La vitesse de l’injection des sprays dans ces conditions est très élevée. En conséquence, des structures énergétiques intermittentes aux petites échelles turbulentes peuvent se manifester dans l’écoulement produit. C’est pourquoi l’accent est mis sur la simulation stochastique des effets turbulents aux échelles non-résolues par LES dans les conditions d’un moteur à injection directe. L’impact de ces effets sur l’atomisation primaire et secondaire, la dispersion des gouttelettes et leur vaporisation représente l’élément essentiel de cette thèse. Dans le but de modéliser ces effets d’intermittence aux échelles non-résolues, deux différentes approches ont été proposées récemment dans la littérature. Dans la thèse, l’accent est mis sur leur application et une éventuelle amélioration pour les conditions d’un moteur à injection directe. La première approche est LES-SSAM (Stochastic Subgrid Acceleration Model). Contrairement aux LES classiques, la LES-SSAM modélise l’accélération turbulente non résolue par le forçage de sous-maille des équations de Navier-Stokes. Ce forçage représente un processus stochastique de type Ornstein-Uhlenbeck construit de telle façon que les propriétés stochastiques de l’accélération, observées par les expériences et les simulations directes, sont représentées. Une telle LES-SSAM, où l’expression de la norme de l’accélération de sous-maille est modifiée, a été appliquée et testée pour la modélisation de l’écoulement interne de l’injecteur d’une simple configuration. Les résultats ont démontré l’efficacité de cette approche malgré la résolution grossière du maillage. Une autre application de LES-SSAM, dans la thèse, concerne sa combinaison avec la méthode VoF pour la simulation de l’écoulement à l’interface au voisinage de l’injecteur. Ici aussi, l’efficacité de cette combinaison a été démontrée en comparaison avec l’expérience et les méthodes numériques actuellement employées pour la simulation de l’atomisation primaire. La deuxième approche abordée dans la majeure partie de la thèse, et qui vise aussi à représenter les effets de l’intermittence aux échelles non-résolues, se base sur la formulation stochastique de la dynamique des gouttes en pulvérisation et en vaporisation, tout en couplage two-way avec l’écoulement turbulent. Les travaux contribuent à la vérification et l’amélioration de cette formulation stochastique. Ainsi le modèle stochastique d’atomisation secondaire est contrôlé par le processus stochastique log-normal pour la dissipation visqueuse. La même variable est la variable-clé pour le modèle de dispersion de gouttes, ces dernières étant soit inférieures soit supérieures à l’échelle de Kolmogorov. La dernière situation a été décrite par la modification de l’équation de mouvement d’une goutte. Enfin, un nouveau modèle stochastique de vaporisation des gouttes, dont le mélange turbulent fait partie du modèle, a été proposé et testé. Tous ces modèles stochastiques ont été implantés dans le code OpenFoam puis testés en comparaison avec d’autres modèles et avec les données expérimentales présentées par le réseau Engine Combustion Network (ECN). L’avantage de l’application de ces modèles sur les maillages à la résolution grossière a été clairement démontréThis thesis concerns with the Large Eddy Simulations (LES) of fuel sprays in direct-injection engines. Given the high injection velocities of sprays, the resulting turbulent flow may be characterized by energetic intermittent structures at small spatial scales. Therefore, the emphasis in this thesis is put on stochastic simulation of turbulent effects on unresolved scales in the engine relevant conditions. The impact of this effect on spray primary and secondary atomization, on droplets dispersion and evaporation represents the main focus in this thesis. The further assessment and modification of two different approaches, developed recently, was the main objective in this thesis. The first one is addressed to LES-SSAM (stochastic sub-grid acceleration model) approach, in which the Navier-Stokes equations are forced on residual scales. This forcing is given by the Ornstein-Uhlenbeck stochastic process constructed in a way to represent the stochastic properties of the subgrid acceleration, known from the experiment and DNS. In the framework of this approach, with the expression of the acceleration norm modified for the wall-bounded conditions, the first step concerned the simulation of the nozzle internal flow on the coarse grid. The results showed the efficiency of this approach. Another step in this part was to combine LES-SSAM with the interface tracking VOF method in the simulation of the near-field of the spray. The performed assessment of this approach in comparison with measurements and with alternative approaches known from the literature demonstrated a potential of such combination of two methods. The second approach in this thesis, in which the intermittency effects on residual scales are also on target, concerned the stochastic modeling of the secondary breakup, dispersion and evaporation of droplets; introducing the two-way coupling between droplets and a highly turbulent flow. Here, the assessment and further development of stochastic models of droplets represent the main contribution in this thesis. So, the model of the secondary breakup is controlled by the stochastic log-normal process for the viscous dissipation rate. The same stochastic variable is the key variable for the dispersion model of droplets below and above the Kolmogrov scale. The droplet equation of motion for the latter case was modified addressing the significant role to simulation the stochastic direction of the droplet acceleration. Finally, the new stochastic model of the turbulent evaporation, in which the stochastic mixing process is a part of the evaporation model, is also represented in this thesis. The different stochastic models outlined above are assessed in comparison to the state-of-art models available in literature and the experiments of Engine Combustion Network (ECN). The results have shown that stochastic models give a good representation of both macroscopic and microscopic spray characteristics on relatively coarse grids
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Frenzel, Erik. "Co-Simulation von LIGGGHTS® und SimulationX® zur Simulation des Zerkleinerungsprozesses in Brechern." Universitätsbibliothek Chemnitz, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-206919.
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In vielen Bereichen der Tagebautechnik spielt die Zerkleinerung von Material/ -strömen eine wesentliche Rolle, wobei sich je nach Material verschiedene Anforderungen an das Brechersystem ergeben. In Folge dessen werden Brecher auftragsspezifisch, meist für einen speziellen Gesteinstyp oder Einsatzort entwickelt oder modifiziert. Eine aussagekräftige Prognose der im Bruchprozess auftretenden Lasten auf den Brecher ist somit essentieller Bestandteil im Entwicklungsprozess.
Ein viel versprechender Ansatz, um das Materialverhalten in der Lastprognose zu berücksichtigen, ist die numerische Simulation des Materialbruchverhaltens mit Hilfe der Diskreten-Elemente-Methode (DEM). Das Verhalten der sogenannten Partikel wird über Kontakt- und bond-Modelle beschrieben und soll das makroskopische Verhalten des jeweiligen Gesteins möglichst realitätsnah abbilden.
Die Problematik ist, dass in SimulationX® keine Module zur DEM-Simulation vorhanden sind und umgekehrt in der DEM-Simulationsumgebung LIGGGHTSG® (LAMMPS improved for general granular and granular heat transfer simulations) keine derartige Maschinensimulation möglich ist. Der Ausweg ist die Co-Simulation zweier unterschiedlicher Simulationsumgebungen durch die Nutzung des ,,Functional Mock-Up Interface“-Standards (FMI).
Berechnungsergebnis sind die dynamischen Lasten auf den Brecher unter Berücksichtigung des Materialverhaltens. Somit können früher in der Brecherentwicklung Prognosen zu auftretenden Lasten getroffen und Einflussuntersuchungen von Maschinenkonfigurationen zur Effizienzsteigerungen durchgeführt werden, was zuvor auf Grund des Einzelanfertigungscharakters nicht möglich oder nicht wirtschaftlich war.
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Jiang, Wenbiao. "Simulation du bullage dans un photobioréacteur." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLC086/document.
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Au cours des dernières années, la culture de microalgues est largement étudiée pour produire des biocarburants et d’autres produits de valeur en fixant le dioxyde de carbone de l’atmosphère, afin d’atténuer simultanément les effets du changement climatique et de réduire la dépendance à l’égard des carburants fossiles. En comparaison avec les systèmes ouverts, les photobioréacteurs fermés sont davantage utilisés en laboratoire, car ils permettent de contrôler avec précision les facteurs environnementaux tels que le pH, la concentration en éléments nutritifs, etc. Le principe de fonctionnement d’un photobioréacteur repose sur l’injection de bulles dans le milieu de culture pour (i) apporter du dioxyde de carbone aux cellules (ii)agiter le liquide. Par l’apport d’énergie lumineuse les cellules transforment le carbone inorganique en carbone organique par photosynthèse. Ainsi, les phénomènes physiques - l’écoulement, transfert de matière, transfert radiatif - et les phénomènes biologiques - photosynthèse, croissance cellulaire et mort - coexistent dans un photobioréacteur. Plus important encore, tous les phénomènes de base ne sont pas complètement indépendants les uns des autres. Des recherches récentes ont révélé que le comportement des bulles avait également une incidence directe sur le processus biologique. En raison du comportement significatif des bulles sur la productivité d'un photobioréacteur, la génération de bulles a été étudiée dans cette thèse au moyen de méthodes expérimentales et numériques.Dans l'étude expérimentale, nous avons conçu puis fabriqué un nouveau photobioréacteur afin d'étudier le bullage in situ. L’emploi d’une technique d’ombroscopie couplée à une caméra vidéo a permis l’enregistrement de séries de bulles. Les images traitées ont permis de mesurer des caractéristiques de bulles (fréquence, volume, facteur de forme). Le volume moyen de bulle et la fréquence de formation de bulles augmentent avec le débit de gaz. De plus, la distribution volumique monodisperse à faible débit devient de plus en plus polydisperse par l’accroissement de celui-ci. L’évolution de la forme des bulles lors de leur remontée dans le liquide a été évaluée par l’emploi de facteurs de forme. Ces facteurs diminuent avec la remontée des bulles et traduisent une déformation horizontalement. A débit élevé, les formes des bulles oscillent et coalescent plus fréquemment.La simulation du bullage a été réalisé par l’emploi d’une méthode Volume of Fluid (VOF) et d’une bibliothèque open source de mécanique numérique des fluides OpenFOAM. Ces choix de méthodes sont motivés en raison de la robustesse d'OpenFOAM en matière de simulation d'écoulements diphasiques rapportée dans la littérature. Une première étude numérique de simulation 2D a permis de déterminer les valeurs appropriées des paramètres numériques (nombre de Courant et la taille du maillage) tout en minimisant le temps de calcul par rapport à une pré-étude 3D. Sans surprise, nous avons déterminé que la taille des mailles devait être inférieure au diamètre de la buse pour obtenir des résultats significatifs. De façon plus surprenante, nous avons observé que le nombre maximum de Courant n’a pas d’importance particulière pour ces simulations (dans une limite raisonnable : 0 à 1). Les simulations 3D ont été menées sur un supercalculateur. Elles ont montré que le volume des bulles et l’évolution de leur forme calculées numériquement étaient en accord avec les résultats expérimentaux. Cependant, les simulations 3D n’ont pas permis de représenter la polydispersité de la distribution volumique des bulles en raison d’un temps de calcul nécessaire trop important pour générer une population de bulles suffisamment nombreuse. Au final, l'outil numérique a aussi été utilisé avec succès pour explorer plusieurs caractéristiques hydrodynamiques de mélange dans le liquideThe working principle of a typical photobioreactor is to inject gas bubbles into the culture medium, providing CO2 to the cells and also stirring the liquid. Subsequently, the cells convert inorganic carbon into organic carbon through photosynthesis under illumination. Therefore, physical phenomena, e.g. bubbly flow, mass transfer, radiative transfer, and biological phenomena, e.g. photosynthesis, cell growth and death, coexist in a photobioreactor. More importantly, all the basic phenomena are not completely independent to each other. For example, bubble volume and bubble shape can influence gas-liquid mass transfer according to Young-Laplace equation and Henry's law. Moreover, some recent research revealed that bubble behaviors also directly affect the biological process. In view of the important impact of bubble behaviors on productivity of a phototbioreactor, the bubbly flow was investigated in this thesis by both experimental and numerical methods.In the experimental study, we first manufactured a new photobioreactor in order to study the bubbles and other phenomena. Subsequently, the bubbles were captured by high speed camera by virtue of a shadowgraphy technique and bubble behaviors were obtained by processing and analyzing the images. From the experimental results, we found that both averaged bubble volume and bubbling frequency increased with gas flow rate. Furthermore, we also discovered that the distribution of bubble volume was almost monodisperse at low flow rate, and it became more and more polydisperse with increasing flow rate. Regarding bubble shape evolution, we used two shape factors, viz. aspect ration and circularity, to quantitatively study it. We found that both shape factors dropped rapidly during bubble rising (within the limit of the field of view of our video camera), which implied that bubbles were flattened in the course of rising. Nonetheless, bubbles became more vertically elongated at higher flow rate, partially due to the more frequent bubble coalescence at higher flow rate.In the numerical study, we adopted VOF method and OpenFOAM, an open source CFD library, as our numerical tool to represent bubbly flow. First of all, the robustness of OpenFOAM in simulating two-phase flow was validated by literature survey. Subsequently, 2D simulations were carried out for seeking the appropriate and not very time-consuming numerical parameters, i.e. maximum Courant number and mesh size. We found that mesh size should somehow be smaller than the nozzle diameter to have meaningful results. On the other hand, maximum Courant number had no particular importance in the simulations (as long as between 0 and 1). Furthermore, 3D simulations were in good agreement with the experiments in terms of bubble volume and bubble shape evolution. However, 3D simulations were not able to represent the polydispersity of bubble volume due to the limited computing power. In addition, several hydrodynamic characteristics were also explored by the proposed numerical tool, which gave reasonable results.To conclude, bubble behaviors were successfully captured by experimental methods and represented by numerical methods in this thesis, which will help us go further in understanding the complicated physical-biological phenomena of a photobioreactor
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Cho, Min Hyun. "Numerical simulation of arc welding process and its application." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1155741113.
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Xu, Yang. "Normal impact of liquid droplets on smooth solid surfaces." Thesis, Paris Est, 2018. http://www.theses.fr/2018PESC1099/document.
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Dans le cadre de la modélisation et de l’expérimentation multi-échelles (projet LabEx MMCD pour les matériaux pour la construction durable) de l’Université Paris-Est Marne-la-Vallée, cette thèse de doctorat vise à modéliser et caractériser les micro-matériaux conçus par impact de gouttelettes de céramique fondue. Les applications de ces matériaux revétus de couches minces sont des traitements de surface pour la construction durable tels que la protection anti-corrosion, les barrières thermiques, le traitement du verre ou les renforts mécaniques. En particulier, nous nous concentrons sur la physique associée à la dynamique des gouttelettes liquides (l'aire de contact et le temps de contact entre la gouttelette et la surface) en effectuant une série de simulations numériques pour les écoulements diphasiques à petite échelle avec le code maison Thetis. Nous avons considéré des variations des conditions d'impact initiales ainsi que l’influence des forces d'inertie, capillaire et visqueuses sur la dynamique des gouttelettes. Nous nous sommes intéressés en particulier au diamètre d'étalement maximal, au temps d’étalement maximal et au temps de contact, sur des surfaces solides de mouillabilité variable. Le code est basé sur l’utilisation d’une méthode Volume-Of-Fluid. Il introduit une fonction auxiliaire régularisée pour estimer la courbure locale et la normale à l'interface. Les principaux liquides de référence adoptés sont l'eau et la céramique fondue, l'eau est choisie pour valider notre code en comparant les simulations aux résultats expérimentaux. La céramique fondue est adoptée car elle est largement utilisée en projection thermique pour créer des barrières thermiques et chimiques (couches anti-oxydantes) ainsi que des renforts mécaniques sur des échantillons spécifiques. Nous nous concentrons sur les cas où les surfaces sont hydrophobes, même si les cas hydrophiles sont également considérés dans les configurations de validation pour des raisons de généralité. Egalement, en introduisant une partie de calcul de l'énergie dans la thèse, une analyse énergétique détaillée de la gouttelette après l'impact est effectuée dans les phases d'étalement et de rétraction pour bien comprendre la dynamique à l'intérieur de la gouttelette. Nous trouvons que le temps de projection est inversement proportionnel à la vitesse d’impact, indépendamment de l’angle de contact lors de l’étalement au temps courts. Une nouvelle mise à l'échelle entre l'étalement maximal et le temps d'étalement est proposée. Celle-ci s'accorde très bien avec les résultats expérimentaux. Par ailleurs, nous introduisons cette mise à l’échelle dans une classe de modèle basée sur la conservation de l’énergie pour prédire l’étalement maximal adimensionné, ce qui permet de mieux prévoir l’étalement maximal adimensionné. Pour finir, une mise à l'échelle du temps de contact est proposée en termes de nombre d'Ohnesorge et de ReynoldsUnder the framework of the LabEx Multi-Scale Modelling and Experimentation of Materials for Sustainable Construction, of Université Paris-Est Marne-La-Vallée, the present PhD thesis aims at modelling and characterizing micro-material designed by impact of molten ceramic droplets. The applications of thin coating materials are surface treatments for sustainable construction such as anti-corrosion, heat barrier, glass treatment or mechanical reinforcement of specific structures.In particular, we focus on the physics behind the liquid droplets' dynamics (the contact area and the contact time between the droplet and surface) by conducting a series of small scale multiphase flow numerical simulations with home-made code Thetis. All simulations are axisymmetric. We have considered variations of initial impact conditions, and studied the influence of inertial, capillary and viscous forces on the droplets' dynamics, especially the maximum spreading diameter, spreading time and the contact time, on solid surfaces. The code is based on Volume-Of-Fluid techniques and introduces an auxiliary smooth function to estimate the local curvature and the normal to the interface. The major reference liquid adopted are the water and the molten ceramic, the water is chosen to validate our code against available experiments at the beginning. The molten ceramic is adopted as it is widely used in thermal spray to built thermal and chemical barriers (anti-oxidant layers) as well as mechanical reinforcements on specific samples. We focus on the cases in which the surfaces are hydrophobic, even if hydrophilic cases are also considered in validation configurations for the sake of generality. Meanwhile, by introducing an energy calculation part in the code, a detailed energetic analysis of the droplet after impact is performed in both the spreading and retraction stage to have a deep understanding of the dynamics inside the droplet.We find the jetting time is inversely proportional to the impact velocity, independent of the contact angle in the early spreading. A new scaling between maximum spreading and spreading time is observed, and agrees well with experimental results. Further, we introduce this scaling into the model based on energy conservation to predict the maximum spreading factor, which provides better prediction on maximum spreading factor than existing literature references. Also a scaling of contact time is proposed in terms of Ohnesorge number and Reynolds number
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Malan, Leon. "Direct numerical simulation of free-surface and interfacial flow using the VOF method : cavitating bubble clouds and phase change." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066555/document.
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La présente étude se fonde sur la méthode du volume de fluide (en anglais VOF pour Volume-of-Fluid), proposée à l'origine par Hirt et Nicols. L'objectif de la première partie de ce travail est l'étude hydrodynamique de la cavitation isotherme dans les grands nuages de bulles. Cette étude s'inscrit plus généralement dans un large effort de recherche en micro--écaillage mené par le CEA. Une méthode capable de traiter la présence de cavités de vapeur de volume variable ou encore de pores a été formulée et implémentée dans un code existant, PARIS. L'écoulement est idéalisé en supposant un liquide parfait, des effets thermiques négligeables et une pression de vapeur nulle. Une étude innovante est présentée, traitant de l'interaction du nuage de bulles dans un liquide en expansion par simulation numérique directe. Les résultats des simulations révèlent l'existence d'un concours de cavités dans un certain régime caractérisé par le nombre de Weber.Dans la deuxième partie de l'étude, le système d'équations à résoudre est modifié et généralisé afin de décrire l'écoulement incompressible d'un fluide diphasique tout en incluant la possibilité d'un changement de phase à l'interface. Une nouvelle méthode VOF est proposée, dans laquelle une nouvelle technique d'advection de la fonction VOF permet de traiter à la fois la conservation de la masse et de l'énergie sous une forme conservative. Les expériences numériques démontrent la précision, la robustesse et la généralité de la méthode proposée, et témoignent d'un développement fondamental important pour l'application des méthodes VOF à la modélisation des changements de phaseDirect numerical simulation of two-phase ow is used extensively for engineering research and fundamental fluid physics studies [54, 81]. This study is based on the Volume-Of-Fluid (VOF) method, originally created by Hirt and Nicols [30]. This method has gained increased popularity, especially when geometric advection techniques are used coupled with a planar reconstruction of the interface [14, 89]. The focus of the first part of this work is to investigate the hydrodynamics of isothermal cavitation in large bubble clouds, which originated from a larger study of micro-spalling [61], conducted by the French CEA. A method to deal with volume-changing vapour cavities, or pores, was formulated and implemented in an existing code, PARIS . The ow is idealized by assuming an inviscid liquid, negligible thermal effects and vanishing vapour pressure. A novel investigation of bubble cloud interaction in an expanding liquid using direct or detailed numerical simulation is presented. The simulation results reveal a pore competition, which is characterised by the Weber number in the ow. In the second part of the study the governing equations are extended to describe incompressible ow with phase change [79]. The description of the work commences with the derivation of the governing equations. Following this, a novel, geometric based, VOF solution method is proposed. In this method a novel way of advecting the VOF function is invented, which treats both mass and energy conservation in conservative form. New techniques include the advection of the interface in a discontinuous velocity field. The proposed algorithms are consistent and elegant, requiring minimal modifications to the existing code. Numerical experiments demonstrate accuracy, robustness and generality. This is viewed as a significant fundamental development in the use of VOF methods to model phase change
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Sarret, Frédéric. "Simulation numérique de dépôts céramiques plasma." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0066/document.
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Cette thèse apporte une contribution à la simulation numérique de la construction de dépôts dans le cadre de la projection plasma type APS (Atmospheric Plasma Spraying). Ce travail est focalisé sur la construction d’un volume représentatif du revêtement en prenant en compte l’ensemble des phénomènes propres au procédé, tels que la nature de l’écoulement de gaz, la cinétique (multiphasique, mouillabilité) et la thermique (transferts thermiques, résistance thermique de contact, solidification) durant l’impact et l’empilement de particules. Une méthode numérique particulière, appelée VOF-SM (Volume Of Fluid - Sub Mesh), est développée. La simulation de l’impact d’un jet instationnaire et turbulent de plasma ArH2 sur un substrat a été réalisée pour définir la nature de l’écoulementen proche paroi et le transfert thermique entre cet écoulement et le substrat. Les phénomènes propres à l’impact de particules ont été intégrés au code de calcul Thétiset validés indépendamment par comparaison à des solutions analytiques et combinés par comparaison à un cas d’étude expérimentale millimétrique. Enfin, une étude d’impacts successifs de particules de Zircone Yttriée sur un substrat en acier a été menée, par une approche en similitudes thermique et cinétique pour pallier la difficulté de la résolution à petites échellesThis PhD thesis is a contribution to the numerical simulation of the plasma sprayedcoating build-up by APS process (Atmospheric Plasma Spraying). This work focuses onthe build-up of a representative volume of the coat considering a great range of phenomenonappearing in APS process such as gas flow properties, kinetic (multiphase flow,wettability) and thermal (heat transfers, thermal contact resistance, solidification) duringthe impact and steaking of particles. An original numerical method, named VOF-SM(Volume Of Fluid - Sub Mesh) is developped. The simulation of the impact of an unsteadyand turbulent ArH2 plasma flow is carried out in order to define the gas flow closeto the wall and heat transferred to the substrate by the plasma. Specific phenomena of theimpact of particles were incorporated into the CFD code (Thétis) and validated independentlyby caparison with analytical solutions, then together combined by the comparisonto a millimeter size impact experimental data. Finally, a study of successive impacts ofYttria-Stabilized Zirconia particles onto a steel substrate was carried out by thermal andkinetic approach similarities to overcome the difficulty of resolving small scales
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Chmura, Thorsten. "Analyse, Modellierung und Simulationen von Routenwahlverhalten / Analyses, Modelling and Simulation of Route Choice Behaviour." Gerhard-Mercator-Universitaet Duisburg, 2005. http://www.ub.uni-duisburg.de/ETD-db/theses/available/duett-05152005-222337/.
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This thesis will give an overview about the connection of physics and economy in special view of human behavior in traffic scenarios. Main topic is the human decision making process in a two-route-choice scenario. In three main Experiments, human players had to decide between two routes which connect two cities. The first experiment is defined by a pure Nash-equilibrium and 18 participants, the second experiment is similar, but alternating construction sites on both routes were added. Experiment 1 and 2 are played over 200 periods. The third experiment is a minority game with mixed equilibria and 9 participants. Experiment 3 was played over 100 periods. Furthermore the first experiment was extended to a larger group of players up to 90 persons. For every experiment two treatments with 6 observations were played. The treatments differ in the given information to the participants before they choose between the two routes. In the first treatment the information about the own travel time was given, additionally in the second treatment the information about travel times on both routes were given. The second part of the thesis describes the statistical data and illustrates the results. Two main results are that the equilibrium was not stable in the experiments, the fluctuations persists to the end of every observation. Further on two player types were found and explained in this chapter. In the third part of this thesis an extended payoff-sum model is described and explained. Simulations using this reinforcement learning model were run and show the reproducibility of the empirical data. In the conclusions the main results are shown and discussed.
Books on the topic "VOF simulations"
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M, Rolfe J., and Staples K. J, eds. Flight simulation. Cambridge [Cambridgeshire]: Cambridge University Press, 1986.
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Košturiak, Ján, and Milan Gregor. Simulation von Produktionssystemen. Vienna: Springer Vienna, 1995. http://dx.doi.org/10.1007/978-3-7091-9413-3.
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Bartel, Dirk. Simulation von Tribosystemen. Wiesbaden: Vieweg+Teubner, 2010. http://dx.doi.org/10.1007/978-3-8348-9656-8.
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Laschet, Andreas. Simulation von Antriebssystemen. Berlin, Heidelberg: Springer Berlin Heidelberg, 1988. http://dx.doi.org/10.1007/978-3-642-83531-5.
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Pfeiffer, Wolfgang. Simulation von Meßschaltungen. Berlin, Heidelberg: Springer Berlin Heidelberg, 1994. http://dx.doi.org/10.1007/978-3-642-48396-7.
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Seel, Christian. Visuelle Simulation von Dienstleistungsprozessen. Lohmar: J. Eul, 2002.
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Hänsel, Matthias. Simulation des Bruchverhaltens von Umformwerkzeugen. Berlin: Springer, 1993.
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Lechmann, Achim, ed. Simulation und Aufladung von Verbrennungsmotoren. Berlin, Heidelberg: Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-79287-1.
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Potchinkov, Alexander. Simulation von Röhrenverstärkern mit SPICE. Wiesbaden: Vieweg+Teubner, 2009. http://dx.doi.org/10.1007/978-3-8348-9613-1.
Full textBook chapters on the topic "VOF simulations"
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Weyer, Johannes, Marlon Philipp, and Fabian Adelt. "Agent-Based Modelling of Infrastructure Systems." In Metropolitan Research, 155–66. Bielefeld, Germany: transcript Verlag, 2022. http://dx.doi.org/10.14361/9783839463109-009.
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Die agentenbasierte Modellierung (ABM) hat sich als eine neuartige Methode zur Untersuchung der Strukturen und Dynamik komplexer Systeme im Allgemeinen sowie soziotechnischer Systeme im Besonderen etabliert. Der Beitrag stellt am Beispiel der Verkehrssimulation einige grundlegende Prinzipien und Methoden von ABM vor. Ferner bietet er einen Überblick über unterschiedliche Simulations-Frameworks (z.B. NaSch, MATSim und SimCo), deren Zweck es ist, Verkehrssysteme zu modellieren und das ABM-Konzept zu nutzen, um unterschiedliche Strategien der politischen Förderung nachhaltiger Transformation zu untersuchen.
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Mansuy, Marc, Maxim Candries, Katrien Eloot, and Sebastien Page. "Simulation Study to Assess the Maximum Dimensions of Inland Ships on the River Seine in Paris." In Lecture Notes in Civil Engineering, 186–200. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-19-6138-0_17.
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AbstractTraversing the river Seine in Paris is challenging for inland navigation vessels due to the density and diversity of local traffic and the variety of manoeuvres to be encountered in a confined environment. The waterway authority, Voies Navigables de France (VNF), commissioned a study to assess the relevance of the current regulations when present and future vessels of varying types and dimensions cross Paris. This paper describes the use of fast time and real time simulations to assess the maximum dimensions of ships crossing the Seine in Paris. In a first phase, fast time simulations were executed with a track controller, which allowed to identify bottlenecks on the full length (12 km) of the river Seine in Paris. Based on those results, critical scenarios were selected to be tested on a full mission bridge simulator by skippers familiar with the crossing of Paris. Inspired by PIANC INCOM WG 141 Detailed Design and Safety and Ease Approaches, the main challenges related to the simulation setup and the assessment methodology are presented and discussed in this paper. The simulations have shown that the main bottlenecks are related to the succession of passages under narrow bridges with non-aligned openings. The maximum water levels for which safe passage is possible, were determined for each ship type and compared with the existing regulations. Finally, recommendations were formulated, which were then discussed with VNF, end users and stakeholders.
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Stille, Karl Stephan. "Simulation." In Energiemanagement von Haushaltsgroßgeräten, 121–35. Berlin, Heidelberg: Springer Berlin Heidelberg, 2018. http://dx.doi.org/10.1007/978-3-662-56398-4_7.
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Laschet, Andreas. "Anwendung von Simulationstechniken." In Fachberichte Simulation, 3–6. Berlin, Heidelberg: Springer Berlin Heidelberg, 1988. http://dx.doi.org/10.1007/978-3-642-83531-5_2.
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Schmidt, Bernd. "Simulation von Produktionssystemen." In Fachberichte Simulation, 1–45. Berlin, Heidelberg: Springer Berlin Heidelberg, 1988. http://dx.doi.org/10.1007/978-3-642-83598-8_1.
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Witte, T. "Die Modellierung von Lagerhaltungssystemen mit den Netzwerkelementen von SLAM II — Überlegungen zum interaktiven Generieren von Simulationsmodellen —." In Fachberichte Simulation, 200–212. Berlin, Heidelberg: Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-662-09906-3_14.
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Schmidt, Bernd, and Chengyan Shi. "Die Modellierung von Produktionsanlagen." In Fachberichte Simulation, 168–81. Berlin, Heidelberg: Springer Berlin Heidelberg, 1992. http://dx.doi.org/10.1007/978-3-642-88184-8_12.
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Koops, Wolfgang. "Simulation von leitungsvermittelten Telekommunikationsnetzen." In Fachberichte Simulation, 119–27. Berlin, Heidelberg: Springer Berlin Heidelberg, 1992. http://dx.doi.org/10.1007/978-3-642-88184-8_8.
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Dörnhöfer, K. "Lösung von Optimierungsproblemen durch Simulation." In Fachberichte Simulation, 61–69. Berlin, Heidelberg: Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-662-09906-3_5.
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Fischer, Jürgen. "Die statistische Auswertung von Simulationsdaten." In Fachberichte Simulation, 391–412. Berlin, Heidelberg: Springer Berlin Heidelberg, 1988. http://dx.doi.org/10.1007/978-3-642-83598-8_17.
Full textConference papers on the topic "VOF simulations"
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Li, Zhong, Rajeev K. Jaiman, and Boo Cheong Khoo. "Simulations of Air Cavity Dynamics During Water Entry and Slamming." In ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/omae2014-23635.
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An adaptive mesh refinement based Volume-of-Fluid (VOF) two-phase method has been employed to simulate the water entry and slamming problems of solid bodies with various geometries. The computations have been performed by using the GFS (Gerris Flow Solver) libraries. Solid boundaries or the interfaces between the solid and the fluid are tracked by a piece-wise linear volume-of-fluid method. The key ingredient in this simulation study is the capability of parallel adaptive refinement along the free-surface interface to capture the interface conditions accurately while using the Eulerian grid based VOF approach. The novelty of this work is that it is the first time to apply GFS libraries and adaptive VOF in solving complex water entry problems to the best of our knowledge. Before applying to a particular application, the adaptive VOF solver is validated by simulating the vertical water entry of a circular disk. The simulations of solid bodies with different geometries such as thin plates are then conducted to investigate the physics of air-cushioning effect during slamming.
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Visone, M., P. Bertetti, P. L. Ausonio, P. L. Ausonio, C. Falletta, D. Paterna, and R. Savino. "VoF-Dynamic Mesh Simulations of Unsteady Ship Hydrodynamics." In CFD 2005- CFD Technology in Ship Hydrodynamics. RINA, 2005. http://dx.doi.org/10.3940/rina.cfd.2005.6.
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Gorlé, Catherine, Hyoungsoon Lee, Farzad Houshmand, Mehdi Asheghi, Kenneth Goodson, and Pritish R. Parida. "Validation Study for VOF Simulations of Boiling in a Microchannel." In ASME 2015 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems collocated with the ASME 2015 13th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/ipack2015-48129.
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This paper presents a comparison of Volume-of-Fluid simulation results with experiments [1] for two-phase flow and heat transfer in a micro channel. Mass transfer between the phases is modeled using a reduced-order model, requiring the definition of a time relaxation constant, r. A two-step solution procedure is used, where first a fixed temperature boundary condition is imposed at the heater to avoid overheating of the device during the initial development of the two-phase flow. After obtaining a quasi-steady-state solution this is changed to a heat flux boundary condition to determine the final solution. Results using three different values for r indicate that the value of the constant should vary throughout the domain. A final simulation where r is defined as a function of the streamwise location results in a prediction of the base temperature within 1K of the experimental result, a pressure drop within 30%, and a prediction of the location of transition from subcooled to saturated flow within 2mm.
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Takahashi, Shigeo, Yasuo Kotake, Ryuichi Fujiwara, and Masahiko Isobe. "PERFORMANCE EVALUATION OF PERFORATED-WALL CAISSONS BY VOF NUMERICAL SIMULATIONS." In Proceedings of the 28th International Conference. World Scientific Publishing Company, 2003. http://dx.doi.org/10.1142/9789812791306_0115.
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Nicoli, A., K. Singh, R. Jefferson-Loveday, S. Ambrose, and S. Mouvanal. "Numerical Simulation of Multi-Scale Oil Films on a Rotating Cup Using VOF and Coupled Eulerian Thin-Film-DPM Approaches." In ASME Turbo Expo 2022: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/gt2022-82533.
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Abstract In this study, the newly developed Nottingham Gas Turbine and Transmission Research Centre (G2TRC) Bearing Chamber Test Module is presented and investigated computationally. The module houses a rotating cup and shaft configuration in order to simulate the droplet generation processes from an aeroengine bearing. The objective of this paper is to model the thin film that develops over the rotating cup surface, comparing a high-fidelity Volume of Fluid (VOF) approach against the Eulerian Thin-Film Model (ETFM). Whilst a VOF approach has previously demonstrated good accuracy for modelling of films over a rotating surface, the ETFM can provide a comparable solution at a much-reduced computational cost. Simulations are performed over a range of shaft speeds and oil flow rates to represent engine operating conditions. This study presents the very first simulation of an oil film over a rotating cup geometry, with a shaft running through the centre of the cup. Computationally, a VOF periodic sector is compared to ETFM simulations run on an equivalent 30° periodic domain. At planes before the rotating cup edge, both film thicknesses and axial velocities are compared. The high-fidelity VOF simulations demonstrate that with an increase in rotational speed, the film thickness over the rotating cup reduces; whilst an increase in oil flow rate produces a thicker film. Compared to the high-fidelity VOF simulations, the ETFM provides good agreement in terms of both film thickness and axial velocities. Overall, the ETFM is shown to be able to produce a similar film to the VOF approach at a much-reduced computational cost, offering a numerical speed-up of approximately 200 to 300 times.
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Wheeler, Miles P., Philip Ryan, Flavio Cimolin, Andrew Gunderson, and John Scherer. "Using VOF Slip Velocity to Improve Productivity of Planing Hull CFD Simulations." In SNAME International Conference on Fast Sea Transportation. SNAME, 2021. http://dx.doi.org/10.5957/fast-2021-013.
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Use of Computational fluid dynamics (CFD) tools is becoming common practice in the analysis of high speed craft. These numerical tools are of great value, since they can provide high-fidelity insight into performance of various designs by modelling non-linear effects due to viscous forces and turbulence. However, CFD tools are often seen as computationally expensive and prohibitive in a design environment. One of the main issues that impacts the use of CFD tools is numerical ventilation, when air is artificially entrained beneath the hull while using the Volume of Fluid (VOF) scheme to model the free surface. To overcome this issue, traditionally, very fine grids are requested near the surface of the hull to resolve the flow. In this paper, it will be illustrated how the use of an algebraic VOF slip velocity, in conjunction with a tight overset model and adaptive mesh refinement prevent the issue of numerical ventilation while simultaneously using a more computationally efficient mesh that produces accurate results in calm water resistance calculations. A verification and validation process comparing the VOF slip velocity method against experimental data for a known hull was conducted. Computational cost and accuracy associated with VOF slip velocity is discussed. The methodology is then applied to a stepped hull and comparisons between towing tank experiments and simulation results are looked at.
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Law, Deify, and Thomas G. Shepard. "Three-Dimensional Volume of Fluid Simulations of Air Bubble Dynamics in a Converging Nozzle." In ASME 2018 5th Joint US-European Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/fedsm2018-83180.
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The present work relates to the dynamics of single bubbles accelerating through a converging nozzle. There are two main aspects to this study. First, this expands upon a previously used two-dimensional model [1] by providing three-dimensional volume of fluid (VOF) simulations that show better agreement with experiments. The VOF model is employed to perform simulations using the commercial computational fluid dynamics (CFD) code ANSYS FLUENT. Second, the present work uses experimental high-speed camera results in conjunction with simulation results to demonstrate bubble time trace and velocity information. Time series of the average liquid velocity at the atomizer exit orifice when the bubble exits as determined via simulation are reported. The passing of a bubble through the nozzle is found to cause a significant fluctuation in the exit velocity that is coupled to the liquid and gas dynamics upstream of the exit.
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Witbeck, Brandon, and D. Keith Walters. "An Improved Bounded Gradient Maximization Method for Interface-Capturing VOF Simulations." In ASME 2009 Fluids Engineering Division Summer Meeting. ASMEDC, 2009. http://dx.doi.org/10.1115/fedsm2009-78393.
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A new high-resolution spatial discretization scheme is presented for the volume-of-fluid (VOF) method. This scheme is an adaptation of the previously published bounded gradient maximization (BGM) scheme [1]. This scheme resolves the phase interface without any explicit geometrical reconstruction of the interface. A net upwind bias in each cell ensures the stability of the scheme, and face limiting satisfies the boundedness criteria at the cell faces to prevent variable overshoot. In contrast to most existing methods, no method using “switching” between upwind-biased and downwind-biased discretization is employed to gain method stability. This paper presents the initial development and implementation of a time-dependent version of the method. Test cases are performed for a number of 2-D and 3-D two-phase flows on both structured and unstructured meshes. Results indicate that the method performs well in maintaining the resolution of the phase interface.
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Pernod, Laetitia, Matthieu Sacher, Jeroen Wackers, Benoit Augier, and Patrick Bot. "Free-Surface Effects on Two-Dimensional Hydrofoils by RANS-VOF Simulations." In SNAME 24th Chesapeake Sailing Yacht Symposium. SNAME, 2022. http://dx.doi.org/10.5957/csys-2022-012.
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Foiling yachts and crafts are both very sensitive to the flying height in terms of stability and performance, raising the scientific issue of the influence of the free-surface when the foil is at low submergence. This work presents numerical simulations of a 2D hydrofoil section NACA0012 at 5° angle of attack in the vicinity of the free surface, for different values of the submergence depth, for a chord-based Froude number of 0.571 and a Reynolds number of 159,000. URANS equations are solved with a mixture model to capture the free surface, and using an automatic grid refinement. Verification of the numerical model and validation with data from the literature are presented. Deformation of the free surface and alteration of the hydrodynamic forces compared to the deep immersion case are observed for a submergence depth-to-chord ratio h/c lower than 2. The foil drag increases up to more than three times the infinite-depth value at h/c ≈ 0.5. The lift force slightly increases until h/c around 1, and then decreases sharply. For h/c < 0.5, the pressure field around the foil is totally modified and the lift is swapped to downward. The study highlights the importance of considering the effect of finite submergence to compute foils’ hydrodynamic forces, for example to be used in Velocity Prediction Programs (VPP) of foiling crafts.
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Clauss, Gu¨nther F., Christian E. Schmittner, and Robert Stu¨ck. "Numerical Wave Tank: Simulation of Extreme Waves for the Investigation of Structural Responses." In ASME 2005 24th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2005. http://dx.doi.org/10.1115/omae2005-67048.
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For the deterministic analysis of extreme structure behavior, the hydrodynamics of the exciting wave field, i. e. pressure and velocity fields, must be known. Whereas responses of structures, e. g. motions, can easily be obtained by model tests, the detailed characteristics of the exciting waves are often difficult to determine by measurements. Therefore, numerical wave tanks (NWT) promise to be a handy tool for providing detailed insight into wave hydrodynamics. In this paper different approaches for numerical wave tanks are introduced and used for the simulation of rogue wave sequences. The numerical wave tanks presented are characterized by the following key features: a) Potential theory with Finite Element discretization (Pot/FE); b) Reynolds-Averaged Navier-Stokes Equations (RANSE) using the Volume of Fluid (VOF) method for describing the free surface. For the NWT using the VOF method three different commercial RANSE codes (CFX, FLUENT, COMET) are applied to calculate wave propagation, whereas simulations based on potential theory are carried out with a wave simulation code developed at Technical University Berlin (WAVETUB). It is shown that the potential theory method allows a fast and accurate simulation of the propagation of nonbreaking waves. In contrast, the RANSE/VOF method allows the calculation of breaking waves but is much more time-consuming, and effects of numerical diffusion can not be neglected. To benefit from the advantages of both solvers, i. e. the calculation speed (Pot/FE-solver WAVETUB) and the capability of simulating breaking waves (RANSE/VOF-solver), the coupling of both simulation methods is introduced. Two different methods of coupling are presented: a) at a given position in the wave tank; b) at a given time step. WAVETUB is used to simulate the propagation of the wave train from the start towards the coupling position (case A) or until wave breaking is encountered (case B). Subsequently, the velocity field and the contour of the free surface is handed over as boundary (case A) or initial values (case B) to the RANSE/VOF-solver and the simulation process is continued. To validate these approaches, different types of model seas for investigating wave/structure interactions are generated in a physical wave tank and compared to the numerical simulations.
Reports on the topic "VOF simulations"
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Goldsman, David, Keebom Kang, and Andrew F. Seila. Cramer-Von Mises Variance Estimators for Simulations. Fort Belvoir, VA: Defense Technical Information Center, September 1993. http://dx.doi.org/10.21236/ada278799.
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Banta, H. G., David B. Troillet, Neil T. Heffernan, Brian Plamondon, and Scott A. Beal. The Virtual Observer/Controller (VOC): Automated Intelligent Coaching in Dismounted Warrior Simulations. Fort Belvoir, VA: Defense Technical Information Center, December 2004. http://dx.doi.org/10.21236/ada429445.
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Banta, H. G., David B. Troillet, Jason P. Daly, and Glenn A. Martin. Virtual Observer Controller (VOC) for Small Unit Infantry Laser Simulation Training. Fort Belvoir, VA: Defense Technical Information Center, April 2007. http://dx.doi.org/10.21236/ada469326.
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Guidati, Gianfranco, and Domenico Giardini. Verbundsynthese «Geothermie» des NFP «Energie». Swiss National Science Foundation (SNSF), January 2020. http://dx.doi.org/10.46446/publikation_nfp70_nfp71.2020.4.de.
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Die oberflächennahe Geothermie mit Wärmepumpen ist Stand der Technik und in der Schweiz bereits stark verbreitet. Im künftigen Energiesystem soll zusätzlich die mitteltiefe bis tiefe Geothermie (1–6 km) eine wichtige Rolle spielen. Im Vordergrund steht die Lieferung von Wärme für Gebäude und industrielle Prozesse. Diese Form der Erdwärmenutzung setzt einen gut durchlässigen Untergrund voraus, damit ein Fluid – in der Regel Wasser – die natürlich vorhandene Gesteinswärme übernehmen und an die Oberfläche transportieren kann. Bei Sedimentgesteinen ist dies meist von Natur aus gegeben, wogegen bei Graniten und Gneisen die Durchlässigkeit mittels Einpressen von Wasser künstlich herbeigeführt werden muss. Die so gewonnene Wärme nimmt mit zunehmender Bohrtiefe zu: In 1 km Tiefe liegt die Untergrundtemperatur bei ca. 40 °C und in 3 km Tiefe bei ca. 100 °C. Um eine Dampfturbine für die Stromproduktion anzutreiben, sind Temperaturen von über 100 °C notwendig. Da dafür grössere Tiefen von 3 bis 6 km erforderlich sind, steigt auch das Risiko der durch die Bohrungen induzierten Seismizität. Der Untergrund eignet sich ausserdem auch zur Speicherung von Wärme und Gasen, zum Beispiel Wasserstoff oder Methan, sowie zur definitiven Einlagerung von CO2. Dazu muss er ähnliche Voraussetzungen erfüllen wie bei der Wärmegewinnung, zusätzlich ist jedoch eine über dem Reservoir liegende dichte Deckschicht erforderlich, damit das Gas nicht entweichen kann. Im Verbundprojekt «Wasserkraft und Geothermie» des NFP «Energie» wurde vor allem der Frage nachgegangen, wo sich in der Schweiz geeignete Bodenschichten finden, die die Anforderungen der verschiedenen Nutzungen optimal erfüllen. Ein zweiter Forschungsschwerpunkt betraf Massnahmen zur Reduktion der durch Tiefenbohrungen induzierten Seismizität und der daraus folgenden Schäden an Bauten. Im Weiteren wurden Modelle und Simulationen entwickelt, die zu einem besseren Verständnis der Vorgänge im Untergrund bei der Erschliessung und Nutzung der geothermischen Ressourcen beitragen. Zusammengefasst zeigen die Forschungsergebnisse, dass in der Schweiz gute Voraussetzungen vorhanden sind für die Nutzung der mitteltiefen Erdwärme (1–3 km), sowohl für den Gebäudepark als auch für industrielle Prozesse. Auch in Bezug auf die saisonale Speicherung von Wärme und Gasen ist Optimismus angebracht. Die Potenziale für die definitive Einlagerung von CO2 in relevanten Mengen sind demgegenüber als eher limitiert zu bezeichnen. Hinsichtlich der Stromproduktion aus Erdwärme mittels der tiefen Geothermie (> 3 km) besteht noch keine abschliessende Gewissheit, wie gross das wirtschaftlich nutzbare Potenzial im Untergrund wirklich ist. Diesbezüglich sind dringend industriell betriebene Demonstrationsanlagen notwendig, um die Akzeptanz bei der Bevölkerung und bei Investoren zu stärken.
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Judkoff, R., and J. Neymark. Home Energy Rating System Building Energy Simulation Test for Florida (Florida-HERS BESTEST): Tier 1 and Tier 2 Tests; Vol. 1 (User's Manual) and Vol. 2 (Reference Results). Office of Scientific and Technical Information (OSTI), August 1997. http://dx.doi.org/10.2172/15000122.
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Minerale für eine verstärkte Kohlendioxid-Aufnahme des Ozeans. CDRmare, 2022. http://dx.doi.org/10.3289/cdrmare.12.
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Wie viel Kohlendioxid der Ozean aufnehmen kann, ohne dabei stark zu versauern, hängt von der Alkalinität seines Oberflächenwassers ab. Hinter diesem Begriff verbirgt sich die Menge säurebindender mineralischer Bestandteile, die zuvor aus verwittertem Gestein gelöst und in das Meer eingetragen wurden. Die Frage lautet nun: Könnte ein gezielter Eintrag solcher Minerale helfen, die Kohlendioxid-Aufnahme des Ozeans zu steigern, ohne die Chemie und das Leben im Meer aus dem Gleichgewicht zu bringen? In einfachen Modellrechnungen funktioniert dieser Ansatz. Feldversuche aber fehlen bislang ebenso wie realitätsnahe Simulationen und detailliertes Wissen über Folgen und Risiken einer Alkalinitätserhöhung. Die Forschungsmission CDRmare untersucht die Potenziale, Machbarkeit und Nebenwirkungen der verschiedenen Verfahren
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Wissen kompakt, Minerale für eine verstärkte Kohlendioxid-Aufnahme des Ozeans. CDRmare, 2022. http://dx.doi.org/10.3289/cdrmare.11.
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Wie viel Kohlendioxid der Ozean aufnehmen kann, ohne dabei stark zu versauern, hängt von der Alkalinität seines Oberflächenwassers ab. Hinter diesem Begriff verbirgt sich die Menge säurebindender mineralischer Bestandteile, die zuvor aus verwittertem Gestein gelöst und in das Meer eingetragen wurden. Die Frage lautet nun: Könnte ein gezielter Eintrag solcher Minerale helfen, die Kohlendioxid-Aufnahme des Ozeans zu steigern, ohne die Chemie und das Leben im Meer aus dem Gleichgewicht zu bringen? In einfachen Modellrechnungen funktioniert dieser Ansatz. Feldversuche aber fehlen bislang ebenso wie realitätsnahe Simulationen und detailliertes Wissen über Folgen und Risiken einer Alkalinitätserhöhung. Die Forschungsmission CDRmare untersucht die Potenziale, Machbarkeit und Nebenwirkungen der verschiedenen Verfahren.