Дисертації: "Mmodelling and numerical simulation"

1

Pannetier, Valentin. "Simulations numériques standardisées de dispositifs de stimulation électrique cardiaque." Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0352.

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Les maladies cardiovasculaires représentent la principale cause de mortalité dans le monde, responsables d’environ 32% des décès en 2019 selon l’Organisation mondiale de la santé (OMS). Face à ces pathologies, la recherche médicale progresse continuellement pour développer des traitements et des dispositifs toujours plus performants. Parmi ces innovations, les stimulateurs cardiaques implantables jouent un rôle crucial dans le traitement des troubles du rythme cardiaque, en intervenant directement sur le cœur en cas de dysfonctionnement. Cependant, malgré leur importance, le développement de ces technologies reste lent et coûteux. Il faut souvent près d’une décennie entre la conception d’un prototype et sa mise sur le marché, ce qui retarde leur impact sur les vies humaines. Cette thèse s’inscrit dans le cadre du projet européen collaboratif SimCardioTest (EU H2020), dont l’objectif est d’accélérer l’adoption d’outils numériques pour la certification de médicaments et de dispositifs médicaux, tels que les stimulateurs cardiaques implantables. L’un des objectifs principaux du projet est d’intégrer les simulations numériques sous la forme d’essais cliniques in silico dans le processus de certification, afin de rendre ce dernier plus rapide à l’aide d’une plateforme web standardisée. Au cours de cette thèse, plusieurs modèles mathématiques ont été développés et analysés, allant de modèles génériques tridimensionnels à des modèles simplifiés sans dimension spatiale. Tous ces modèles comprennent un circuit électrique inspiré d’un stimulateur cardiaque commercial, des modèles de contacts reproduisant les couches ioniques à la surface des électrodes sous forme de circuits électriques équivalents, ainsi que des modèles de tissu cardiaque avec ou sans propagation spatiale de potentiels d’action cardiaque. La crédibilité de ces modèles est évaluée par des comparaisons avec des expérimentations animales menées durant la thèse, dans le but de démontrer leur capacité à reproduire des stimulations cardiaques réalistes. Ces comparaisons reposent principalement sur les tensions mesurées par les stimulateurs cardiaques et sur l’étude des courbes de seuil, aussi appelées courbes de Lapicque. Ces courbes, largement utilisées en clinique pour ajuster les stimulateurs, établissent la relation entre la durée et l’amplitude de la stimulation nécessaires pour provoquer une contraction cardiaque efficace. Elles permettent en particulier d’optimiser, en personnalisant individuellement, les réglages des stimulateurs, et ainsi de minimiser la consommation d’énergie, maximiser la durée de vie du dispositif, et ainsi améliorer le confort de vie des patients. L’adoption de modèles simplifiés sans dimension constitue une étape stratégique importante de cette thèse. Contrairement aux modèles spatiaux, très coûteux à résoudre numériquement, ces modèles sont plus simples à résoudre et ils ont permis de réaliser plusieurs études paramétriques, notamment pour effectuer une calibration à partir des données expérimentales. Des études supplémentaires de sensibilité, locales et globales, ont également été menées afin d’analyser l’influence et la pertinence des paramètres dans les modèles développés
Cardiovascular diseases are the world’s leading cause of death, responsible for around 32% of all deaths in 2019, according to the World Health Organization (WHO). Faced with these pathologies, medical research is making constant progress to develop ever more effective treatments and devices. Among these innovations, implantable pacemakers play a crucial role in the treatment of cardiac rhythm disorders, intervening directly on the heart in the event of malfunction. Despite, despite their importance, the development of these technologies remains slow and costly. It often takes almost a decade from early prototyping to market launch, delaying their impact on human lives. This thesis is part of the European collaborative project SimCardioTest (EU H2020), which aims to accelerate the adoption of numerical tools for the certification of drugs and medical devices, such as implantable pacemakers. One of the main goals of the project is to integrate numerical simulations in the form of in silico clinical trials on a standardized web plateform in oirder to speed up thecertification process. During of this thesis, several mathematical models were developed and analyzed, ranging from generic three-dimensional models to simplified models with no spatial dimension. All these models include a electrical circuit inspired by a commercial pacemaker, contact models representing the ionic layers on electrode surfaces as equivalent electrical circuits, and cardiac tissue models with or without spatial propagation of cardiac action potentials. The credibility of these models is assessed through comparisons with animal experiments conducted during the thesis, with the aim of demonstrating their ability to reproduce realistic cardiac stimulations. These comparisons are based mainly on the voltages measured by pacemakers and on the study of threshold curves, also known as Lapicque curves. These curves, widely used clinically to adjust pacemakers, establish the relationship between stimulation duration and amplitude required to induce an effective cardiac contraction. In particular, they enable pacemaker settings to be optimized through individual customization, thereby minimizing energy consumption, maximizing device life, and therefore improving patient’s life quality. The adoption of simplified dimensionless models is an valuable strategic step in this thesis. Unlike spatial models, which are very costly to solve numerically, these models are simpler to solve and have enabled several parametric studies to be carried out, in particular to perform calibration using experimental data. Additional sensitivity studies, both local and global, were also carried out to analyze the influence and relevance of the parameters in the developed models

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2

Amphlett, Jonathan Lee. "Numerical simulation of microelectrodes." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341628.

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3

Evensberget, Dag Frohde. "Numerical Simulation of Nonholonomic Dynamics." Thesis, Norwegian University of Science and Technology, Department of Mathematical Sciences, 2006. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9484.

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We study the numerical integration of nonholonomic problems. The problems are formulated using Lagrangian and Hamiltonian mechanics. We review briefly the theoretical concepts used in geometric mechanics. We reconstruct two nonholonomic variational integrators from the monograph of Monforte. We also construct two one-step integrators based on a combination of the continuous Legendre transform and the discrete Legendre transform from an article by Marsden and West. Inintially these integrators display promising behavior, but they turn out to be unstable. The variational integrators are compared with a classical Runge-Kutta method. We compare the methods on three nonholonomic systems: The nonholonomic particle from the monograph of Monforte, the nonholonomic system of particles from an article by McLachlan and Perlmutter, and a variation of the Chaplygin sleigh from Bloch.

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4

Uddholm, Per. "Numerical Simulation of Flame Propagation." Thesis, Uppsala University, Department of Information Technology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-98325.

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The effects of the temperature and length, of the preheat zone, on the deflagration to detonation transition are investigated through numerical simulation. The Navier-Stokes equations, with a reaction term, are solved in one dimension. The time integration is a one-dimensional adaptation of an existing two-dimensional finite volume method code. An iterative scheme, based on an overlap integral, is developed for the determination of the deflagration to detonation transition. The code is tested in a number of cases, where the analytical solution (to the Euler equations) is known. The location of the deflagration to detonation transition is displayed graphically through the preheat zone temperature as a function of the fuel mixture temperature, for fixed exhaust gas temperature and with the preheat zone length as a parameter. The evolution of the deflagration to detonation transition is investigated for an initial state well within the regime where the deflagration to detonation transition occurs. Graphs displaying the temporal evolution of pressure, temperature, reaction rate, and fuel mass fraction are presented. Finally, a method for estimating the flame velocity during the deflagration and detonation phases, as well as the flame acceleration during the intermediate phase, is developed.

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5

Karaismail, Ertan. "Numerical Simulation Of Radiating Flows." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606452/index.pdf.

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Predictive accuracy of the previously developed coupled code for the solution of the time-dependent Navier-Stokes equations in conjunction with the radiative transfer equation was first assessed by applying it to the prediction of thermally radiating, hydrodynamically developed laminar pipe flow for which the numerical solution had been reported in the literature. The effect of radiation on flow and temperature fields was demonstrated for different values of conduction to radiation ratio. It was found that the steady-state temperature predictions of the code agree well with the benchmark solution. In an attempt to test the predictive accuracy of the coupled code for turbulent radiating flows, it was applied to fully developed turbulent flow of a hot gas through a relatively cold pipe and the results were compared with the numerical solution available in the literature. The code was found to mimic the reported steady-state temperature profiles well. Having validated the predictive accuracy of the coupled code for steady, laminar/turbulent, radiating pipe flows, the performance of the code for transient radiating flows was tested by applying it to a test problem involving laminar/turbulent flow of carbon dioxide through a circular pipe for the simulation of simultaneous hydrodynamic and thermal development. The transient solutions for temperature, velocity and radiative energy source term fields were found to demonstrate the physically expected trends. In order to improve the performance of the code, a parallel algorithm of the code was developed and tested against sequential code for speed up and efficiency. It was found that the same results are obtained with a reasonably high speed-up and efficiency.

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6

Riljak, Stanislav. "Numerical simulation of shape rolling." Licentiate thesis, Stockholm, 2006. http://www.diva-portal.org/kth/theses/abstract.xsql?dbid=3963.

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7

Alhajraf, Salem. "Numerical simulation of drifting sand." Thesis, Cranfield University, 2000. http://hdl.handle.net/1826/3502.

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Two-phase flows are involved in many industrial and natural flow phenomena varying from as specific as the transport of crude oil in pipelines to as general as the dispersion of pollutants in the atmosphere. Numerical modelling based on Computational Fluid Dynamics (CFD), has attracted the attention of scientists and engineers from a wide range of backgrounds over recent decades during which these models have been extensively developed, analysed and applied to many practical applications. Wind blown particles such as sand or snow and their resulting accumulation around buildings, roads, oil field installations and security fences causes severe structural and design problems. These are traditionally addressed based on previous experience, full-scale field investigation or using scale model wind tunnel experiments, all of which incur high cost. In this study, wind blown particles are considered as a two-phase flow system. A finite volume based CFD code is developed using two-phase flow theory and is employed to numerically simulate the drifting of sand and snow around obstacles of different geometry. The model solves the governing transport equations in three dimensional space. Three different approaches are investigated to represent and solve the secondary flow phase, particles, within the flow field; a particle tracking model, based on a Lagrangian reference frame and the homogenous and the mixture models, based on an Eulerian reference frame. The capabilities and limitations of each of these models are investigated for flow fields involving drifting particles around obstacles of different geometry. Particles transported by wind both in suspension and saltation are modelled based on the physical characteristic and the threshold condition of the particle. Their effect on the flow field is incorporated through separate source terms contributing to the particle transport equation. The Eulerian based models are coupled with the Fractional Area/Volume Obstacle Representation (FAVOR) as a mean of representing the solid boundary formed by deposited particles separating the flow field from the accumulation zones. The FAVOR treatment allows the flow field to respond to the changes in the geometry of the deposition regions and further calculations take into account the erosion and deposition processes that have previously occurred. The model can be calibrated to match specific flow conditions through several controlling parameters. These controlling parameters are identified and analysed for four distinct case studies. Model results are compared with field and wind tunnel observations available in the literature and with field measurements conducted as a part of this study in the desert of the State of Kuwait. Qualitatively good agreement between the model and the observations is obtained in two as well as three dimensions. Although the mixture and particle tracking models show the potential capability to simulate such flow systems, the homogenous model is found to be the most appropriate model due to its relative simplicity compared to the mixture model and its lower computational cost compared to the Lagrangian particle-tracking model. In conclusion, a practical CFD tool has been developed and validated, incorporating novel physical and numerical models. The tool can be utilised by scientists and engineers to further understand the real world problem of drifting sand and snow in urban and industrial environments.

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8

Matallah, H. "Numerical simulation of viscoelastic flows." Thesis, Swansea University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638026.

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In this thesis, consideration is given to two-dimensional isothermal incompressible flows of rheological complex materials. An introduction is provided on the background rheology and numerical schemes. A time stepping procedure is employed to solve steady state relevant partial differential equations, and in particular the equations of momentum, continuity and the Oldroyd-B constitutive equations. A Petrov Galerkin pressure correction method is used as the base finite element scheme. Model flows, considered as smooth and having analytical solutions are tested for accuracy. In contrast, complex benchmark problems, which may be smooth but with sharp velocity gradients, or alternatively non-smooth, are also solved to test stability and to contrast the quality of results against those in the literature. Despite the considerable effort devoted to establish sophisticated numerical methods to solve highly elastic complex flows of polymeric materials, the simulation of viscoelastic flows through complex geometries remains a challenge. One method that has found favour recently is the elastic-stress-splitting (EVSS) method. There are two features associated with this method, stress-splitting and recovery of velocity gradients. In this thesis, recovery and stress-splitting schemes for plane and axi-symmetric flows of non-Newtonian fluids are presented. Accuracy, stability and numerical performance issues are addressed for different schemes. It is established that recovery-based schemes are stable and superior in higher Deborah number attenuation over conventional and EVSS alternatives. Hence, it is shown that it is the recovery aspect that is responsible for improved stability behaviour. In this context, a 4:1 plane contraction and the flow past a cylinder in an infinite domain are used to analyse vortex activities for Newtonian and viscoelastic flows. Mesh convergence is also analysed.

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9

Jiang, Long. "Numerical simulation of urban flooding." Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504497.

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10

Kovacs, Endre. "Numerical simulation of magnetic nanoparticles." Thesis, Loughborough University, 2005. https://dspace.lboro.ac.uk/2134/7742.

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We solved the Landau-Lifshitz equations numerically to examine the time development of a system of magnetic particles. Constant or periodical external magnetic field has been applied. First, the system has been studied without dissipation. Local energy excitations (breathers) and chaotic transients have been found. The behaviour of the system and the final configurations can strongly depend on the initial conditions, and the strength of the external field at an earlier time. We observed some sudden switching between two remarkably different states. Series of bifurcations have been found. When a weak Gilbert-damping has been taken into account, interesting behaviour has been found even in the case of one particle as well: bifurcation series and period multiplication leading to chaos. For a system of antiferromagnetically coupled particles, highly nontrivial hysteresis loops have been produced. The dynamics of the magnetization reversal has been investigated and the characteristic time-scale of the reversal has been estimated. For more particles, the energy spectrum and the magnetization of the system exhibits fractal characteristics for increasing system size. Finally, energy have been pumped into the system in addition to the dissipation. For constant field, complicated phase diagrams have been produced. For microwave field, it has been found that the chaotic behaviour crucially depends on the parity of the number of the particles.

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11

Kalkanis, P. "Numerical simulation of spoiler flows." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47131.

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12

Jammy, S. P. "Direct numerical simulation of vortices." Thesis, University of Surrey, 2015. http://epubs.surrey.ac.uk/809415/.

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A direct numerical simulation of a Batchelor vortex has been carried out in the presence of freely decaying turbulence, using both periodic and symmetric boundary conditions; the latter most closely approximates typical experimental conditions, while the former is often used in computational simulations for numerical convenience. A recently developed numerical method, based on compact schemes combined with three stage Runge-Kutta method for time integration, with projection method for enforcing continuity is used for numerical simulations. The Poisson solver used is a direct solver in spectral space. The higher-order velocity statistics were shown to be strongly dependent upon the boundary conditions, but the dependence could be mostly eliminated by correcting for the random, Gaussian modulation of the vortex trajectory, commonly referred to as wandering, using a technique often employed in the analysis of experimental data. Once this wandering had been corrected for, the strong peaks in the Reynolds stresses normally observed at the vortex centre were replaced by smaller local extrema located within the core region but away from the centre. Analysis of the budgets of turbulent kinetic energy and normal Reynolds stress suggest that the production budget during the growth phase of vortex development, resembles turbulent boundary layer type budgets. The analysis of the budgets of turbulent shear stresses shows that the formation and organization of `hairpin' (secondary) structures within the core is the main mechanism for turbulent production and the budget of TKE and radial tangential shear stress shows a turbulent boundary layer type budget.

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13

Zurheide, Frank Thomas. "Numerical simulation of aircraft vortices." Aachen Shaker, 2009. http://d-nb.info/998626899/04.

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14

Qu, Bo. "Numerical simulation of axisymmetric turbulence." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEC010/document.

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Pas de résumé
Axisymmetric turbulence is investigated using direct numerical simulations. A fully spectral method is implemented using Chandrasekhar-Kendall eigenfunctions of the curl-operator. The numerical domain is a periodic cylinder with no-penetration and partial slip conditions at the wall. Numerical simulations are first carried out for freely decaying axisymmetric turbulence, starting from a variety of initial conditions. The simulations indicate that the global angular momentum is the most robust invariant of the system. It is further observed that large-scale coherent structures emerge, as in 2D isotropic turbulence. Energy decays more slowly than helicity, and the toroidal kinetic energy decays faster than its poloidal part. In the case where the toroidal kinetic energy becomes negligible, a quasi-two dimensional turbulence in the poloidal plane is obtained, with a behavior compatible with predictions of statistical mechanics theories. Forced and decaying simulations are then carried out to assess the cascade-behavior of the different invariants. The existence of an inverse cascade is shown to explain the robustness of the angular momentum and the possible ‘spontaneous generation’ of this quantity and of circulation in the flow. In helical flows, the existence of a dual cascade is confirmed, with a scenario compatible with the existence of an inverse energy cascade towards the large scales, and a direct cascade of helicity towards the small scales. The inverse energy cascade seems to be mainly associated with the poloidal velocity field. Using a helical decomposition of the flow, it is shown that the direct cascade of helicity seems to subsist even in the absence of net helicity, when the ‘cascade’ of the helicity contained in oppositely polarized modes is considered individually. The scaling of the energy spectra associated with the energy cascade is compatible with elementary dimensional arguments, whereas the scaling of the inverse (presumably helicity) cascade yields an anomalously steep slope. It is shown that this slope adjusts to the value predicted by dimensional analysis when the spectra are computed from a filtered velocity field in which strong intermittent regions of velocity are not accounted for. Finally, a preliminary (but unfortunately unfruitful) attempt is presented to apply a variational principle to the description of turbulent scalar mixing in three-dimensional turbulence

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15

Zeda, Jason D. "Numerical simulation of evaporating capillary jets." Thesis, Springfield, Va. : Available from National Technical Information Service, 1999. http://handle.dtic.mil/100.2/ADA367314.

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16

Segle, Peter. "Numerical simulation of weldment creep response." Doctoral thesis, KTH, Materials Science and Engineering, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3359.

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In-service inspections of high temperature pressureequipment show that weldments are prone to creep and fatiguedamage. It is not uncommon that severely damaged weldments arefound even before the design life of the component has beenreached. In order to improve this situation action has beentaken during the last decades, both from industry, universitiesand research institutes, aiming at an enhanced understanding ofthe weldment response.

The work presented in this thesis focuses on numericalsimulation of weldment creep response. For a more profoundunderstanding of the evolution of creep damage in mismatchedlow alloy weldments, simulations are performed using thecontinuum damage mechanics, CDM, concept. Both design and lifeassessment aspects are addressed. The possibility to assessseam welded pipes using results from tests of cross-weldspecimens taken out from the seam is investigated. It is foundthat the larger the cross-weld specimen the better thecorrelation. The advantage to use the CDM concept prior to aregular creep analysis is also pointed out. In order to developthe CDM analysis, a modified Kachanov-Rabotnov constitutivemodel is implemented into ABAQUS. Using this model, a secondredistribution of stresses is revealed as the tertiary creepstage is reached in the mismatched weldment.

Creep crack growth, CCG, in cross-weld compact tension, CT,specimens is investigated numerically where a fracturemechanics concept is developed in two steps. In the first one,the C^*value and an averaged constraint parameter areused for characterising the fields in the process zone, whilein the second step, the creep deformation rate perpendicular tothe crack plane and a constraint parameter ahead of the cracktip, are used as characterising parameters. The influence oftype and degree of mismatch, location of starter notch as wellas size of CT specimen, is investigated. Results show that notonly the material properties of the weldment constituentcontaining the crack, but also the deformation properties ofthe adjacent constituents, influence the CCG behaviour.Furthermore, the effect of size is influenced by the mismatchof the weldment constituents.

A circumferentially cracked girth weld with differentmismatch is assessed numerically by use of the fracturemechanics concept developed. The results show that type anddegree of mismatch have a great influence on the CCG behaviourand that C^*alone cannot characterise crack tip fields.Corresponding R5 assessments are also performed. Comparisonwith the numerical investigation shows that the assumption ofplane stress or plane strain conditions in the R5 analysis isessential for the agreement of the results. Assuming the formerresults in a relatively good agreement for the axial stressdominated cases while for the hoop stress dominated cases, R5predicts higher CCG rates by an order of magnitude.

Keywords:ABAQUS, constraint effect, continuum damagemechanics, creep, creep crack growth, design, design code,finite element method, fracture mechanics, life assessment,mismatch, numerical simulation, weldment

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17

Reasor, Daniel Archer. "Numerical simulation of cellular blood flow." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42760.

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In order to simulate cellular blood, a coarse-grained spectrin-link (SL) red blood cell (RBC) membrane model is coupled with a lattice-Boltzmann (LB) based suspension solver. The LB method resolves the hydrodynamics governed by the Navier--Stokes equations while the SL method accurately models the deformation of RBCs under numerous configurations. This method has been parallelized using Message Passing Interface (MPI) protocols for the simulation of dense suspensions of RBCs characteristic of whole blood on world-class computing resources. Simulations were performed to study rheological effects in unbounded shear using the Lees-Edwards boundary condition with good agreement with rotational viscometer results from literature. The particle-phase normal-stress tensor was analyzed and demonstrated a change in sign of the particle-phase pressure from low to high shear rates due to RBCs transitioning from a compressive state to a tensile state in the flow direction. Non-Newtonian effects such as viscosity shear thinning were observed for shear rates ranging from 14-440 inverse seconds as well as the strong dependence on hematocrit at low shear rates. An increase in membrane bending energy was shown to be an important factor for determining the average orientation of RBCs, which ultimately affects the suspension viscosity. The shear stress on platelets was observed to be higher than the average shear stress in blood, which emphasizes the importance of modeling platelets as finite particles. Hagen-Poiseuille flow simulations were performed in rigid vessels for investigating the change in cell-depleted layer thickness with shear rate, the Fåhraeus-Linqvist effect, and the process of platelet margination. The process of platelet margination was shown to be sensitive to platelet shape. Specifically, it is shown that lower aspect ratio particles migrate more rapidly than thin disks. Margination rate is shown to increase with hematocrit, due to the larger number of RBC-platelet interactions, and with the increase in suspending fluid viscosity.

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18

Tarhan, Tanil. "Numerical Simulation Of Laminar Reacting Flows." Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/2/12605307/index.pdf.

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Novel sequential and parallel computational fluid dynamic (CFD) codes based on method of lines (MOL) approach were developed for the numerical simulation of multi-component reacting flows using detailed transport and thermodynamic models. Both codes were applied to the prediction of a confined axisymmetric laminar co-flowing methane-air diffusion flame for which experimental data were available in the literature. Flame-sheet model for infinite-rate chemistry and one-, two-, and five- and ten-step reduced finite-rate reaction mechanisms were employed for methane-air combustion sub-model. A second-order high-resolution total variation diminishing (TVD) scheme based on Lagrange interpolation polynomial was proposed in order to alleviate spurious oscillations encountered in time evolution of flame propagation. Steady-state velocity, temperature and species profiles obtained by using infinite- and finite-rate chemistry models were validated against experimental data and other numerical solutions. They were found to be in reasonably good agreement with measurements and numerical results. The proposed difference scheme produced accurate results without spurious oscillations and numerical diffusion encountered in the classical schemes and hence was found to be a successful scheme applicable to strongly convective flow problems with non-uniform grid resolution. The code was also found to be an efficient tool for the prediction and understanding of transient combustion systems. This study constitutes the initial steps in the development of an efficient numerical scheme for direct numerical simulation (DNS) of unsteady, turbulent, multi-dimensional combustion with complex chemistry.

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19

Hamendi, Ahmed. "Numerical Simulation Of Germencik Geothermal Field." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12611386/index.pdf.

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The Germencik Omerbeyli geothermal field is considered to be one of the most important geothermal fields in Turkey. A numerical modeling study was carried out to simulate the response of the field to different production/injection scenarios. The reservoir performance evaluation was based on the numerical simulation of the reservoir behavior using the simulation code TOUGH2. The numerical simulation model includes a total area of 85.8 km2 and extends from the surface at +330 m msl (mean sea level) to a depth of -4581 m msl. Through a trial and error process, the natural state model was satisfactorily matched with the initial temperature and pressure data measured at the wells. The natural state model was further calibrated using the long term flow test (LTFT) data conducted in 2006, including OB-6 and OB-9 as flowing wells and OB-8 as an injection well. The model was then used to predict reservoir performance under different production/injection scenarios over the next 30 years. Forecast runs showed that the pressure declines almost equally in all areas, consistent with the high permeability and connectivity of the reservoir, which had been established from the LTFT.

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20

Vethe, Stine. "NUMERICAL SIMULATION OF FATIGUE CRACK GROWTH." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for produktutvikling og materialer, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18721.

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The purpose of this study was to explore the posibilities and challenges with simulating fatigue crack growth (FCG) by the extended finite element method (XFEM). Another aim was to develope a procedure for XFEM FCG simulations in Abaqus by means of scripting. Finally was the procedure used to simulate FCG in an API standard, cone shaped threaded connection. Different FCG models were reviewed by a limited litterature search and a procedure 2D FCG simulations was carried out by a python script. The procedure succeeded with the simulation of FCG when applied to a model with refined mesh around the crack tip. In the suggested partial tasks of the thesis description were a procedure 3D FCG simulation also suggested, but as this required more computer capacity than available in the study this was not carried out.

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21

Kralj, Cedomir. "Numerical simulation of diesel spray processes." Thesis, Imperial College London, 1996. http://hdl.handle.net/10044/1/7964.

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22

Bekele, Seifu Argaw. "Numerical simulation of an elastic string." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq21153.pdf.

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23

Vuta, Ravi K. "Numerical simulation of moving boundary problem." Link to electronic thesis, 2007. http://www.wpi.edu/Pubs/ETD/Available/etd-050407-082551/.

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24

Hock, Kuah Teng. "Numerical simulation of sand casting process." Ohio : Ohio University, 1987. http://www.ohiolink.edu/etd/view.cgi?ohiou1183046313.

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25

Gault, M. "Numerical simulation of advanced semiconductor devices." Thesis, Swansea University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637032.

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In this thesis the numerical simulation of advanced semiconductor devices is considered. In order to simulate devices such as the semiconductor laser or the electron wave diffraction transistor advanced physical models must be included. These models are first derived and then applied to particular devices of interest. Initally the fundamentals of heterostructure device modelling are considered with descriptions of the control region approximation and the Scharfetter-Gummel algorithm for the calculation of the current densities. This model is then developed to cope with degenerate statistics using an additional parameter in the Maxwell-Boltzmann exponential. To simulate optical devices such as semiconductor lasers the optical field must be known and hence the solution to the wave equation is considered. Two methods are used, the effective and weighted index methods, and it is found that the weighted index method has important advantages for wave guides of reduced size. In either method a one dimensional algebraic eigenvalue equation must be solved and a highly efficient method for the solution to this equation is presented. The thermal properties of buried heterostructure lasers are investigated using a coupled approach to the electrical, thermal and optical equation sets. The lasing mode profiles, carrier distributions, threshold currents and temperature characteristics are analysed and good agreement is found with experimental results, including the temperature dependence of the threshold current and the prediction of a break-point temperature. To model quantum effects Schröinger's equation is solved using the transfer matrix technique and this is coupled with Poisson's equation and the continuity equations. Scattering is introduced via Lorentzian broadening and a new method for incorporating a finite capture time is derived. This model is applied to 'coherent electron emitters' and a new device is proposed which provides highly coherent emission in the direction of propagation.

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26

Johansson, Fredrik. "Numerical simulation of Rosetta Langmuir Probe." Thesis, Uppsala universitet, Rymd- och plasmafysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-206890.

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By modelling and simulating the ESA spacecraft Rosetta in a plasma with solar wind parameters, and simultaneously simulating a particle detection experiment of Langmuir probe voltage sweep type using the ESA open source software SPIS Science, we investigate the features of Rosetta’s envi- ronment in the solar wind and the e↵ect of photoemission from the space- craft on the measurements made by the Langmuir Probe instrument on board Rosetta. For a 10 V positively charged spacecraft and Maxwellian distributed photoelectron emission with photoelectron temperature, Tf = 2 eV in a plasma of typical 1 AU solar wind parameters: ne = 5 ⇥ 106 m3, vSW = 4 ⇥ 105 m/s, Te = 12 eV, Tion = 5 eV, we detect a floating potential of 6.4 (± 0.2) V at Langmuir probe 1. Two models used in literature on photoemission was used and compared and we report a clear preference to the Maxwellian energy distribution of photoelectrons from a point source model with our simulation result.

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27

Anderson, John Murray. "Numerical simulation of imperfect gas flows." Thesis, University of Glasgow, 1992. http://theses.gla.ac.uk/4411/.

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28

Karadimos, Antonis. "Numerical simulation of fibrous filter loading." Thesis, Heriot-Watt University, 2004. http://hdl.handle.net/10399/240.

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29

Mattos, Marcos Andre Da Frota. "Numerical simulation of lightning return stroke." Thesis, University of Nottingham, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328511.

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30

Abercrombie, Stuart Christopher Benedict. "Numerical simulation of diffusion controlled reactions." Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401748.

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31

Angus, John Neil. "Numerical simulation of complex microelectrode geometries." Thesis, University of Southampton, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395996.

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32

Punekar, Jyothika Narasimha. "Numerical simulation of nonlinear random noise." Thesis, University of Southampton, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243151.

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33

ROCHINHA, FERNANDO ALVES. "MODELING AND NUMERICAL SIMULATION OF RODS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1990. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=20299@1.

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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
FUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO
É apresentado um modelo não-linear para estruturas unidimensionais em equilíbrio, onde não são feitas restrições de caráter geométrico. Este modelo é capaz de descrever movimentos que envolvam flexão, torção, cilhamento e extensão. As configurações de referência e deformada têm sua geometria descrita através da posição espacial de uma curva e da orientação de uma base ortonormal associada a cada ponto dessa curva. O uso dos ângulos de Euler na descrição das rotações, o que pode implicar em instabilidades numéricas, é evitado através do uso de uma nova parametrização para o problema. O problema de equilíbrio que envolve o comportamento não-linear de uma estrutura unidimensional é formulado de diferentes maneiras. São apresentados dois métodos numéricos para a solução desse problema. Um deles é baseado numa decomposição via lagrangeano aumentado e outro é um método de Newton não convencional. São discutidos detalhes acerca da implementação computacional desses métodos. A validade das formulações é atestada através de alguns exemplos numéricos. Em particular. São analisadas algumas aplicações relacionadas com operações de cabos umbilicais em prospecção petrolífera, que envolvem carregamentos estáticos complicados como aqueles ocasionados por flutuadores e pela atração gravitacional.
It is presented a model of the static geometrically non-linear behavior of an elastic rod which considers flexion, torsion, shear and tension. The geometry of the body, in the reference and deformed configurations, is described given the position of the centerline and the geometry of a rigid frame attached to each point of the line. A particular parametrization that avoids the difficulties associated with the use of Euler angles is employed simplifying the numerical treatment. The equilibrium problem for a nonlinear rod is formulated in several different ways and two numerical methods for solution of these problems are presented. One is based on augmented Lagrangian splitting and the second is a non-standard Newton’s method. Details pertaining to the implementation of that method are discussed. A number of numerical simulations have been documented to demonstrate the robustness of the formulations. In particular, some applications in connection with Off shore pipe lines operations, which involves complicated static loading conditions that includes floaters and gravitational forces, are analysed.

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34

Theobald, Mark A. "A numerical simulation of diesel autoignition." Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/15017.

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Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1986.
MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING
Bibliography: leaves 94-98.
by Mark A. Theobald.
Sc.D.

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35

Lau, K. D. "Numerical simulation of mitral valve function." Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1346461/.

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In the mammalian heart there are four heart valves (HV), of which the largest is the mitral valve (MV). Key components in the circulatory system, correct HV function is vital to cardiovascular health. A tethered and asymmetric structure, the MV regulates unidirectional flow between the left atrium and left ventricle. MVfunction is divided between systole/closure, where theMVis required to sustain a pressure load ~120 mmHg whilst minimising flow reversal, and diastole/opening in which the MV is required to rapidly transition from closed to open in order to maximise the transport of blood. Directly affecting the heart, dysfunction of the MV can affect either opening or closing through stenoses or prolapse/regurgitation respectively. Complementing experimental techniques, numerical simulation of theMVoffers additional insights into MV function as unmeasurable variables such as the stresses can be approximated. Due to the immersed nature of the HVs, numerical simulation of the MV requires an approach that is able to model both the large deformation of the MV and non–uniform haemodynamics pressure load resulting from the blood/HV contact. In this work the finite element solver LS–DYNA has been used as it addresses both issues. Using this framework, anatomically sized MV models have been used to characterise the current methodology of reported HV simulations, showing that the fluid–structure interaction (FSI) modelling of the blood/HV contact is essential in the simulation of MV dynamics. Application of this FSI method has been applied to surgical repair technique of the MV known as the edge–to–edge repair, showing that more invasive procedures result in greater stress concentrations but impaired the flow rates. Further advances in this model have been used to examine growth and remodelling effect of the MV tissue in both normal and dysfunctional states.

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36

Lin, Xiaobin. "Numerical simulation of fatigue crack growth." Thesis, University of Sheffield, 1995. http://etheses.whiterose.ac.uk/14437/.

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This thesis describes the advances made by the author on the direct modelling of the fatigue growth of planar cracks A versatile step-by-step 3D finite element technique has been developed, which calculates the stress intensity factors at a set of points on the crack front according to linear elastic fracture mechanics principles and then applies a fatigue crack growth la\v to this set of points to obtain a new crack profile The software DUCK developed has a good capability of automatic remeshing so that the fatigue propagation of arbitrary shaped cracks can be conveniently followed The stress intensity factor calculation using the 3D finite element method has been improved and widely verified to be of good accuracy generally, which provides an important guarantee for the fatigue growth prediction. Several major problems associated with the stress intensity factor calculation, such as crack front definition, free surface layer and mesh abutting the crack front, as well as J-integral path independence, have been discussed A variety of cracked geometries of either theoretical or practical significance have been modelled by the numerical technique, including internal defects in infinite solids, surface cracks in finite thickness plates, round bars and pressure vessels, and initially multiple surface small cracks. Many results useful for the fatigue assessment of each kind of crack, such as stress intensity factor variations, fatigue shape changes and fatigue lives, have been obtained. By comparing with existing numerical methods and some limited experimental data found in the literature, it is shown that the numerical simulation technique is reliable and can predict the fatigue propagation of complex crack configurations, which is seldom possible for methods with assuming crack front configurations Meanwhile, due to the highly automated procedure or the technique, it has become straightforward to model the fatigue growth of practical cracked components, as demonstrated by the computations in this thesis. It is believed that such a numerical simulation technique has a great potential and will play an useful role in the area of fatigue study and assessment.

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37

Galleni, Francesco. "Numerical simulation of vertical intermittent flows." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/49209.

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The present research extends the application of the “slug capturing” technique, already extensively validated for the prediction of horizontal slug flow, to the case of vertical pipes. In this technique, the one-dimensional two fluid model is solved numerically in order to simulate mechanistically the growth and development of the structures which characterise the vertical intermittent flow, such as slugs and waves. In this work the technique is first successfully applied to the prediction of vertical slug flow: it is shown here that, when the appropriate correlation for the interfacial friction forces is used, the slug capturing technique is able to simulate correctly – even in vertical configurations - the complete evolution of the slugs and to predict their key characteristics with a notable accuracy when compared against experimental data. This represents certainly the most important achievement of this work. The one-dimensional two-fluid model is well known to be ill-posed and hence, as the mesh is refined, artificial instabilities may grow so as to render the simulation unreliable. For this reason, a Von Neumann analysis of the discretized form of the model is presented. It is shown that the discretization introduces a cut-off limit for short wavelengths, below which all the perturbations are damped. It is suggested here that this effect, for practical sizes of the mesh, is sufficient to stabilize the system. Furthermore, this work presents preliminary results of the application of the technique to churn flow. It is shown that, although the results may be considered promising, the model still needs development.

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38

Keshtiban, Ibrahim Jalili. "Numerical simulation of compressible viscoelastic flows." Thesis, Swansea University, 2004. https://cronfa.swan.ac.uk/Record/cronfa43047.

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In this work, we first present a brief introduction to flow at low Mach numbers, followed by rheological and equations of states for dense materials. Subsequently, we provide the background theory over several difficult issues encounter by compressible schemes, at low Mach numbers (singular limit of compressible flows). This would include key modifications employed to rectify density-based schemes and extending pressure-based incompressible algorithms for dealing with compressible flows. To accommodate weakly-compressible viscoelastic/viscous flows at low Mach numbers, a high-order time-marching pressure-correction algorithm has been adopted, in semi-implicit form. For discretisation of velocity and pressure equations, over the fractional stages of this pressure correction scheme, a Galerkin finite element was employed. To accommodate stress equations (considered here in Oldroyd-B form) two spatial discretisation alternatives are adopted. This encompasses a mixed finite element formulation in SUPG form, with a quadratic stress and velocity interpolations. The second scheme involves a sub-cell finite volume implementation, a hybrid fe/fv scheme for the full system. For both scheme variants, enhanced velocity gradients are acquired, via a recovery technique. Two discrete representations are proposed to interpolate density: a piecewise-constant form with gradient recovery and a linear interpolation form, akin to that on pressure. Validation on a numbers of classical benchmark problems bear out the high quality of performance of both compressible flow implementations, at low to vanishing Mach number. Neither linear, nor constant density interpolation schemes degrade the second-order accuracy of the original incompressible fractional-staged pressure-correction scheme. In viscous context, we conduct several tests on cavity and contraction flows (both Cartesian and cylindrical coordinates) for both compressible and incompressible flow settings. To validate results of our original incompressible scheme, for the cavity test problem, we compare and contrast predicted velocity fields with those in the literature. For this test problem, the effect of singularity in boundary conditions is investigated on spatial accuracy for both incompressible and compressible flows with the two density interpolations. On contraction flows, consistency is confirmed according to the two different forms of density interpolation. Capability of the scheme in dealing with very low Mach number flows is demonstrated, via adjusting Tait parameters. The scheme responses well as Mach number approaches zero (incompressible limit), and there is no obvious minimum threshold on Mach number for this scheme. We have conducted several tests, under the compressible settings on the effect of system eigenvalues on convergence patterns.

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39

Karlsson, Karl. "Numerical Simulation of Sabot Discard Projectile." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-79248.

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When designing an armour piercing kinetic energy projectile with a discarding sabot, it is important to know how the projectile is affected by the sabot during the discard. If the projectile has no active guiding systems, small disturbances to the initial flight path of the projectile can result in a significant deviance from its intended target. To investigate whether the discard process and its effect on a projectile could be simulated a CFD model was built based on a generic design for an APFSDS projectile for the Carl Gustaf M4 system built by Saab Dynamics AB. The model had to replicate the course of a sabot discard as accurately as possible and be able to track how it affects the projectile. ANSYS Fluent was used to build a model of a quarter of the design incorporating one of the four sabot petals and the part of the projectile in between two of its four fins, utilizing symmetry at zero angle of attack. To achieve a realistic discard process, fluents 6DOF solver was used allowing the sabot to discard due to aerodynamic loads rather than by following a pre-determined path. To allow the components to move inside the domain an overset interface was implemented around the sabot to allow the mesh to update itself during the simulation, keeping its quality consistent. The models initial stage includes a small gap between the sabot and projectile which is necessary to avoid contact which causes issues with mesh creation and divergence. The projectile geometry was based on rough estimates of how a fin stabilized projectile for the M4 would look whereas the sabot design was based on earlier sabot designs and iterated to achieve a discard phase with no contact. The iterative process which produced the sabot design proved that its geometry greatly affects how it discards from the projectile. To track how the projectile is affected during the discard, the forces and moments applied to the projectile from the flow including its interaction with the sabot were tracked. To compare there forces and moments for different discard courses, the sabots centre of gravity was changed to provoke it to discard differently. The model showed a clear difference in how the projectile was affected by the flow during the different discards. This shows the importance of designing the sabot to discard cleanly and quickly so as to not alter the trajectory of the projectile in flight. Also investigated was the effect of the initial gap on the course of the discard. Adding the gap is a simplification which should affect the discard so that it no longer matches a physical test case and so will have to be tuned to find what gap provides the most realistic discard. Although this model could not be validated given the lack of a physical counterpart, it could be determined that the gap greatly affects the discard and that this model is very sensitive to the initial load put on the sabot. Before the model can be used for concept development, a few things need to be worked out. These include a contact definition, inner ballistic effects and building a model that can be test fired to generate validationdata.

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40

Etekpo, Kossi. "Numerical solution for subsurface reservoir simulation." Master's thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/25007.

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Transport problems in porous media constitute an important field of scientific research in modern world, due to their broad applications in area such as petroleum engineering, water resources, pollutants transport and green- house gases sequestration to just mention few. The mathematical models that describe such problems have been developed and form one of the main classes of partial differential equations (PDEs) that scientists encounter in the real-world modeling. Nevertheless, in most of the cases, the exact solutions in the classical sense of those models are not available. The study of numerical approximation of PDEs is therefore an active research area and there is an extensive literature on numerical methods for PDEs. In this work, we review some numerical techniques, more precisely we present finite volume method with two-point flux approximation and mixed finite volume method for spatial discretization of elliptic and parabolic PDEs modeling transport flow in porous media. We then present some standard explicit and implicit methods, Rosenbrock schemes and exponential time stepping schemes for temporal discretization. We finally run some numerical simulations of advection-diffusion-reaction problems in a heterogeneous and an anisotropic porous media.

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41

Mitchell, Colin Raymond. "Numerical Simulation of Calcium Carbonate Formation." University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1294360826.

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42

Berry, Bruce. "Numerical Simulation of Metallic Uranium Sintering." Thesis, University of Arkansas, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10278377.

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Conventional ceramic oxide nuclear fuels are limited in their thermal and life-cycle properties. The desire to operate at higher burnups as is required by current utility economics has proven a formidable challenge for oxide fuel designs. Metallic formulations have superior thermal performance but are plagued by volumetric swelling due to fission gas buildup. In this study, we consider a number of specific microstructure configurations that have been experimentally shown to exhibit considerable resistance to porosity loss. Specifically, a void sizing that is bimodally distributed was shown to resist early pore loss and could provide collection sites for fission gas buildup. We employ the phase field model of Cahn and Hilliard, solved via the finite element method using the open source Multi-User Object Oriented Simulation Environment (MOOSE) developed by INL.

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43

Messig, Danny. "Numerical simulation of pulverized coal combustion." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2017. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-228707.

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Die Arbeit befasst sich mit der Flamelet Modellierung für die Verbrennung von Kohlenstaub. Dabei liegt der Fokus sowohl auf der detaillierten Betrachtung der Gasphasenchemie als auch auf der Interaktion der Kohle mit der Gasphase. Ziel der Arbeit ist die Entwicklung einer Methode für die Simulation großtechnischer Kohlestaubfeuerungen. Die energetische Umsetzung von Kohle läuft in drei wesentlichen Schritten ab: Verdampfung der Feuchtigkeit, Ausgasung der Kohle (Pyrolyse) und schließlich der Koksabbrand. Da die Struktur der Kohle als fossiler Brennstoff hoch komplex ist, existieren viele prädiktive, rechenaufwändige Modelle zur Beschreibung dieser Prozesse [1–4]. Diese Modelle können nicht direkt in numerischen Strömungssimulationen genutzt werden, dienen aber zur Kalibrierung einfacherer kinetischer Modelle. Diese in der Arbeit angewendete Prozedur wird in [5] beschrieben. Zur detaillierten Beschreibung des Abbaus der entstehenden höheren Kohlenwasserstoffe werden in der Simulation große Reaktionsmechanismen benötigt. Die Benutzung solcher Mechanismen ist mit großen Rechenzeiten verbunden und daher bleibt deren Anwendbarkeit auf einfache Anwendungsfälle beschränkt. Der Vorteil der Flamelet Modellierung besteht darin, dass unter bestimmten Voraussetzungen der komplette thermo-chemische Zustand, bestehend aus Temperatur, Druck und Zusammensetzung, mit nur wenigen charakterisierenden Kontrollvariablen abgebildet werden kann. Durch Vorgabe und Variation der Kontrollvariablen können diese Zustände mittels kanonischer Flammenkonfigurationen vorberechnet und in sogenannten Flamelettabellen abgespeichert werden. Für das klassische Flamelet / Fortschrittsvariablen Modell [6] wird der thermo-chemische Zustand über Mischungsbruch und Fortschrittsvariablen parametriert, dabei bestimmt der Mischungsbruch den Anteil an Brenn- stoff im Gemisch und die Fortschrittsvariable den Fortschritt der chemischen Reaktion. Die Kontrollvariablen werden in der numerischen Simulation transportiert, an Stelle der Energie- und Speziesgleichungen. Dies stellt für große Mechanismen eine dramatische Reduktion der zu lösenden Gleichungen dar. Der thermo-chemische Zustand ergibt sich per Look-up aus den Flamelettabellen. Im Zuge der Verbrennung trockener Kohle werden zwei Brennstoffe durch Pyrolyse und Koksabbrand freigesetzt. Für die Flamelet Modellierung bedeutet dies entsprechend je einen Mischungsbruch für Pyrolysegas und Produkte aus dem Koksabbrand. Neben der Fortschrittsvariablen wird ebenfalls die Enthalpie der Gasphase als Kontrollvariable benötigt aufgrund des intensiven Wärmeaustauschs zwischen Kohle und Gasphase. In der Arbeit erfolgt die Vorstellung der benötigten Transportgleichungen sowie die Beschreibung verschiedener Methoden zur Integration nicht-adiabater Zustände in Flamelettabellen. Dabei unterscheiden sich die vorgestellten Tabellierungstrategien hauptsächlich in der betrachteten Verbrennungsart. IV Erfolgt die Mischung von Brennstoff und Oxidationsmittel erst in der untersuchten Flammenkonfiguration, spricht man von Diffusionsflammenstrukturen; sind beide schon gemischt, so entstehen Vormischflammenstrukturen. Die Detektion solcher Strukturen erfolgt in der Arbeit anhand einer Flammenstrukturanalyse mittels Flammenmarker. Die prinzipielle Übertragbarkeit des Flamelet / Fortschrittsvariablen Modells auf turbulente Kohlestaubfeuerung wurde von Watanabe [7] gezeigt, jedoch ist die Bewertung der eingesetzten Flamelet Modellierung in Grobstruktursimulationen nicht ohne weiteres möglich. Deshalb werden zur Verifizierung der entwickelten Tabellierungstrategie in der Arbeit einfache Flammenkonfigurationen betrachtet, die es erlauben, direkte Chemielösungen mit den Lösungen der tabellierten Chemie zu vergleichen. Für den entsprechenden Vergleich erfolgt die Vorstellung zweier Analysen. Bei der a priori Analyse wird der thermo-chemische Zustand der detaillierten Lösung mit dem tabellierten Zustand verglichen. Für den Look-up werden dabei die Kontrollvariablen der direkten Chemiesimulation benutzt. Die a posteriori Analyse ist der Vergleich einer voll gekoppelten Rechnung unter Benutzung der Tabellierungstrategie mit der zugehörigen detaillierten Rechnung. Die erste untersuchte Konfiguration stellt eine Gegenstromanordnung mit vorgewärmter Luft und Kohlebeladung dar. Die Hauptergebnisse dieser rein numerischen Studie wurden bereits veröffentlicht [8] und es konnte die erfolgreiche Applikation der vorgestellten Tabellierungstrategie in dieser Anordnung für Tabellen basierend auf Diffusionflammenstrukturen gezeigt werden. Für die Validierung der detaillierten Rechnungen erfolgt die Nutzung experimenteller Daten [9, 10] für magere Methan-Sauerstoff-Stickstoff Mischungen in Staupunktströmungen. Es zeigt sich, dass diese Konfigurationen stark von den vorgemischten Gasflammen dominiert werden und somit Tabellen basierend auf Vormischflammenstrukturen einzusetzen sind. Die entwickelte Tabellierungsmethode ist in der Lage, auch diese Flammenstrukturen abzubilden. Abschließend wird numerisch eine Parametervariation hinsichtlich Einlassgeschwindigkeit und Kohlebeladung vorgestellt, um die Robustheit und breite Anwendbarkeit der entwickelten Tabellierungstrategie aufzuzeigen. Zusammenfassend konnte mittels Flammenstrukturanalyse für jede vorgestellte Konfiguration der zu verwendende Typ der Tabelle bestimmt werden. In den untersuchten Konfigurationen führte deren Anwendung zu einer guten Übereinstimmung mit den detaillierten Rechnungen. Damit legt diese Arbeit den Grundstein für weiterführende Betrachtung zur Simulation großtechnischer Kohlestaubfeuerungen.

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44

Zhao, Gang. "Numerical simulation of complex channel flows /." May be available electronically:, 2007. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.

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45

Ramamoorthy, Babila. "Numerical simulation of radiative heat transfer." Birmingham, Ala. : University of Alabama at Birmingham, 2008. https://www.mhsl.uab.edu/dt/2009r/ramamoorthy.pdf.

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46

ZHUANG, YA-SHU, and 莊雅淑. "Numerical bathymetric simulation." Thesis, 1988. http://ndltd.ncl.edu.tw/handle/47067358808839053648.

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47

Lai, Jian Fan, and 賴建帆. "CCN numerical simulation." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/56032769498430844173.

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48

Kuo, Chih-Wei, and 郭志暐. "Numerical simulation of nonwetting." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/t326xf.

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博士
國立中央大學
機械工程研究所
94
This present study was conducted by numerical simulation to discuss the isothermal and thermocapillary nonwetting phenomena. An interstitial film, induced either by shear stress or thermocapillary convection, forming the droplet nonwetting.

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49

Tang, Szu-Wei, and 唐思維. "Numerical Simulation of Supersonic." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/36065365371163826389.

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Анотація:

碩士
國立交通大學
機械工程系
88
Numerical Simulation of Supersonic Clean Bench Student: Szu-Wei Tang Advisor: Wu-Shung Fu Department of Mechanical Engineering National Chiao Tung University Abstract High-frequency megasonic cleaning is now an essential technology for semiconductor processing. Despite an abundance of empirical data and industry experience, a thorough understanding of the fundamentals of megasonic cleaning has proven elusive. The aim of the study is to investigate the flow properties during the Supersonic transducer operated and the mechanical effects on wafer in the clean bench by utilized a CFD code of “Star-CD.” The transducer is simulated by a wall subjected to a periodic velocity varying with time. From the results of the simulation, it can be found that the cleaning efficiency is significantly influenced by the geometry of the clean bench, and the pressure waves in the flow field can produce much thinner boundary layers and increase shear stress on the wall.

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Harris, Nancy E. "Numerical simulation of cold surges." Thesis, 1985. http://hdl.handle.net/10945/21471.

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Дисертації з теми "Mmodelling and numerical simulation"

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