Dissertationen zum Thema „Numerical platforms“
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Ozec, Mustafa Onur. „Direction Finding Performance Of Antenna Arrays On Complex Platforms Using Numerical Electromagnetic Simulation Tools“. Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613740/index.pdf.
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An important step for the design of direction finding systems is the performance evaluation
using numeric electromagnetic simulation tools. In this thesis, a method is presented for both
modeling and simulation in a numeric electromagnetic simulation tool FEKO. The method
relies on the data generated by FEKO. The data is then processed by correlative interferometer
algorithm. This process is implemented in a MATLAB environment. Different types of
antenna arrays including dipole, monopole and discone antennas are used. The antenna arrays
are mounted on a UAV and SUV in order to see the platform effects. The direction finding
performance is evaluated for different scenarios. It is shown that the presented approach is an
effective tool for understanding the direction finding characteristic of antenna arrays.
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Khoueiry, Nicole. „Study of granular platforms behaviour over soft subgrade reinforced by geosynthetics : Experimental and numerical approaches“. Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI027.
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Les géosynthétiques sont utilisés depuis les années 70 dans le renforcement des plateformes granulaires reposant sur des sols de faible portance pour des applications de routes non revêtues. La complexité des mécanismes développés et la diversité des produits de renforcement nécessitent encore d’étudier ces plateformes renforcées. Un essai au laboratoire permettant de tester des plateformes à échelle réelle a été développé. Une plateforme granulaire non revêtue reposant sur un sol de faible portance a été reproduite. Un protocole de mise en place de ce sol a été élaboré pour assurer son homogénéité et la répétabilité des essais. Une instrumentation spécifique a été développée pour collecter le maximum de mesures utiles pour l’interprétation du transfert de charge et du comportement des géogrilles utilisées. Trois types de géogrille ont été testées : une géogrille extrudée et deux géogrilles tricotées de rigidité différente. Après de nombreux essais de faisabilité, dix essais ont été effectués sous un chargement cyclique sur plaque circulaire, la plateforme testée a été placée dans un banc d’essai de 1,8 m de large, 1,9 m de long et 1,1 m de haut. Sur la base du même protocole de mise en œuvre, des essais de circulation avec un Simulateur Accélérateur de Traffic (SAT) ont été effectués. Ce simulateur a été spécifiquement conçu et construit pour cette application. Pour ces essais, la plateforme testée a été placée dans le banc d’essai allongé à 5 m. La plateforme a été soumise à deux types de sollicitations : un chargement cyclique sur plaque et un chargement de circulation. Des essais de répétabilité ont permis de vérifier le protocole mis en place. A partir des essais, plusieurs observations ont pu être faites sur le comportement des plateformes granulaires, le sol peu porteur, et sur l’efficacité du renforcement. De plus, ces essais ont permis de montrer que le chargement de circulation est beaucoup plus endommageant que le chargement sur plaque. Parallèlement à ces essais, un modèle numérique a été développé en se basant sur la méthode des différences finies avec le logiciel FLAC 3D. Cette modélisation a permis de prédire le comportement de la plateforme sous le premier chargement de plaqueGeosynthetics were used since 1970 in the base course reinforcement supported by soft subgrade in unpaved road application. The various factors and parameters influencing the dominant mechanism and its relative contribution on the platform improvement explain the need of more investigations in this topic. In this research work, large-scale laboratory test was developed to study the reinforcement contribution in the unpaved road improvement. Therefore, an unpaved platform was built of 600 mm of artificial subgrade supporting a base course layer. A detailed experimental Protocol was established regarding the soil preparation, the installation and the soils compaction procedure to reproduce the site conditions and insure the platform repeatability for each test. Three geosynthetics were tested first under a cyclic plate load test. Cyclic load was performed on the prepared platform, with a maximum load of 40 kN resulting in a maximum applied pressure of 560 kPa. The platform was subjected to 10,000 cycles with a frequency of 0.77 Hz. An advanced and complete soil instrumentation was provided in order to collect the maximum data needed for thorough analysis. Quality control tests were performed before each test to verify the soil layers homogeneity and properties. Two base course thicknesses were tested under this test condition, 350 and 220 mm. Once the developed protocol was confirmed under the circular plate load tests, further tests using the Simulator Accelerator of Traffic (SAT) were performed. Indeed, the laboratory prepared platform was placed in a larger box of 1.8 m in large, 5 m in length and 1.1 m in height. The prepared platform was subjected to two solicitations: a particular plate and traffic load. The Simulator Accelerator of Traffic was developed specially for this application. A machine that simulates the traffic load under an effective length of 2 m and a velocity of 4 km/h. The two areas were instrumented: the area under the circulation load, and the area under the plat load, located aside. In addition, a numerical model based on the differential element method using FLAC 3D was developed. The model simulated the circular plate load test with the same platform configuration under monotonic load. The results were compared to the first monotonic load applied on the rigid plate experimentally
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Frazer, Miles. „Advances in understanding the evolution of diagenesis in Carboniferous carbonate platforms : insights from simulations of palaeohydrology, geochemistry, and stratigraphic development“. Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/advances-in-understanding-the-evolution-of-diagenesis-in-carboniferous-carbonate-platforms-insights-from-simulations-of-palaeohydrology-geochemistry-and-stratigraphic-development(9a1caa9d-6f16-472a-8b38-42aca657a9b9).html.
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Carbonate diagenesis encapsulates a wide range of water rock interactions that can occur within many environments and act to modify rock properties such as porosity, permeability, and mineralogical composition. These rock modification processes occur by the supply of reactant-laden fluids to areas where geochemical reactions are thermodynamically and kinetically favoured. As such, understanding the development of diagenesis requires an understanding of both palaeohydrology and geochemistry, both of which have their own complexities. However, within geological systems, both the conditions that control fluid migration and the distribution of thermodynamic conditions can change through time in response to external factors. Furthermore, they are often coupled, with rock modification exercising a control on fluid flow by altering the permeability of sediments. Numerical methods allow the coupling of multiple complex processes within a single mathematical formulation. As such, they are well suited to investigations into carbonate diagenesis, where multiple component subsystems interact. This thesis details the application of four separate types of numerical forward modelling to investigations of diagenesis within two Carboniferous carbonate platforms, the Derbyshire Platform (Northern England) and the Tengiz Platform (Western Kazakhstan). Investigations of Derbyshire Platform diagenesis are primarily concerned with explaining the presence of Pb-mineralisation and dolomitisation observed within the Dinantian carbonate succession. A coupled palaeohydrology and basin-development simulation and a series of geochemical simulations was used to investigate the potential for these products to form as a result of basin-derived fluids being driven into the platform by compaction. The results of these models suggest that this mechanism is appropriate for explaining Pb-mineralisation, but dolomitisation requires Mg concentrations within the basin-derived fluids that cannot be attained. Geothermal convection of seawater was thus proposed as an alternative hypothesis to explain the development of dolomitisation. This was tested using an advanced reactive transport model, capable of considering both platform growth and dolomitisation. The results of this suggests that significant dolomitisation may have occurred earlier on in the life of the Derbyshire Platform than has previously been recognised. An updated framework for the development of diagenesis in the Derbyshire Platform is proposed to incorporate these new insights. The Tengiz platform forms an important carbonate oil reservoir at the northeastern shore of the Caspian Sea. The effective exploitation of any reservoir lies in an understanding of its internal distributions of porosity and permeability. Within carbonate systems, this is critically controlled by the distribution of diagenetic products. A model of carbonate sedimentation and meteoric diagenesis is used to produce a framework of early diagenesis within a sequence stratigraphic context. The studies mentioned above provide a broad overview of the capabilities and applicability of forward numerical models to two data-limited systems. They reveal the potential for these methods to guide the ongoing assessment and development of our understanding of diagenetic systems and also help identify key questions for the progression of our understanding in the future.
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Albaiz, Abdulaziz (Abdulaziz Mohammad). „MPI-based scalable computing platform for parallel numerical application“. Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/95562.
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Thesis: S.M., Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (page 61).
Developing parallel numerical applications, such as simulators and solvers, involves a variety of challenges in dealing with data partitioning, workload balancing, data dependencies, and synchronization. Many numerical applications share the need for an underlying parallel framework for parallelization on multi-core/multi-machine hardware. In this thesis, a computing platform for parallel numerical applications is designed and implemented. The platform performs parallelization by multiprocessing over MPI library, and serves as a layer of abstraction that hides the complexities in dealing with data distribution and inter-process communication. It also provides the essential functions that most numerical application use, such as handling data-dependency, workload-balancing, and overlapping communication and computation. The performance evaluation of the parallel platform shows that it is highly scalable for large problems.
by Abdulaziz Albaiz.
S.M.
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Alleau, Thibaut. „Development of a numerical platform to model the mitral valve“. Thesis, Compiègne, 2021. http://www.theses.fr/2021COMP2649.
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L’insuffisance mitrale est la valvulopathie mondiale la plus fréquente avec une prévalence de 2%. Lorsque le patient n’est pas en mesure d’être opéré à cœur ouvert, un implant percutané est utilisé pour aider la fermeture des feuillets. Le seul implant actuellement disponible est basé sur la réparation bord à bord de la valve mitrale. Il réduit le reflux vers l’oreillette lors de la systole, mais n’est pas adapté pour les patients souffrant d’insuffisance mitrale fonctionnelle, chez qui la pathologie provient du ventricule et non des éléments de la valve. L’objectif de la thèse est de fournir une plateforme numérique permettant d’aider au développement d’un implant adapté pour ces patients. Plusieurs géométries de valve ont été réalisées au moyen d’un modèle paramétrique, en utilisant des données anatomiques. La dynamique de la valve a été modélisée avec le logiciel ADINA par des simulations éléments finis en grandes déformations. Des modèles structurels de la valve ont permis de représenter la fermeture de la valve sous une pression uniforme. Les lois de comportement de matériaux ont été développé dans le but d’obtenir une fermeture réaliste de la valve. Cela a nécessité la prise en compte de l’hyperélasticité et de l’anisotropie des tissus. Des pathologies valvulaires, telles que la dilatation de l’anneau mitrale ou la rupture des cordages tendineux ont été modélisées, et plusieurs méthodes ont été testées pour y apposer des systèmes médicaux. En utilisant une description ALE et un couplage monolithique, les interactions fluide-structure ont été simulées pour une valve mitrale bi-dimensionnelle. La fermeture hermétique de la valve pendant la systole a pu être reproduite et l’ouverture de la valve étudiée pendant la diastole. La plateforme numérique développée permet de modéliser la fonction de la valve mitrale et peut être utilisée pour aider au développement d’un implant mitral grâce au modèle paramétrique reproduisant différentes géométries de valve et aux lois matériaux anisotropes. Une perspective reste la création d’un modèle 3D des interactions fluide-structure de la valve mitraleMitral insufficiency is the first valvular disease worldwide, with a 2% prevalence. When open-heartsurgery is impossible for the patient, surgeons use percutaneous devices to help the mitral leaflets coapt. However, the only device currently available is based on the edge-to-edge mitral valve repair technique. This type of implant is not adapted for patients suffering from functional mitral insufficiency, where the ventricle is responsible for the lack of coaptation of the leaflets. This thesis aims to provide a numerical platform to help the development of a mitral valve implant adapted for those patients. Several mitral valve geometries were created from a parametric model using anatomical measurements. Finite element simulations of the mitral valve were performed using ADINA to determine the valve closure under constant pressure. Several material models were developed in large strain and large deformation to model the valve closure accurately. Pathological behaviour such as annulus dilatation and chordae rupture were modelled, and several methods were tested to implement medical devices. Fluid-structure interaction of a 2D mitral valve was obtained using an ALE description and a monolithic coupling approach. Both the systole and the diastole were reproduced and studied, and the hermetic seal of the valve was detailed. The numerical platform developed is suited to model mitral valve function and can be used to help the development of mitral implants. In addition, the parametric geometry model and the anisotropic material model will be useful to depict with realism the valve function. A 3D fluid-structure interaction of the mitral valve could be developed
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Jouan, Marine. „La construction sociale du marché du financement participatif en France“. Electronic Thesis or Diss., Paris, ENST, 2017. http://www.theses.fr/2017ENST0052.
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Depuis la fin des années 2000, les plateformes de financement participatif se développent en France avec la promesse d’une relation directe, désintermédiée, entre demandeurs de financement et financeurs, en facilitant l’accès aux fonds pour des porteurs de projet et en permettant aux Français de financer les projets de leur choix. Cette thèse vise à étudier ce phénomène à partir d’une enquête combinant observation ethnographique et entretiens menés auprès des différents acteurs qui se sont organisés pour faire exister et développer ce secteur d’activité. L’enquête montre que l’institutionnalisation du financement participatif en France résulte d’une action collective impliquant des professionnels du secteur, des représentants des pouvoirs publics, des partenaires de plateformes et des médias. Alors que les plateformes défendent un modèle d’auto-organisation et d’autonomie, il apparaît que le développement des plateformes n’aurait pas été possible sans l’intervention des pouvoirs publics qui ont créé un cadre juridique favorable au financement participatif, au nom d’une volonté de faire évoluer le rapport des Français à leur épargne et d’amener ces derniers à contribuer à la santé économique des entreprises dans un contexte de crise. L’enquête montre aussi que par-delà l’extrême hétérogénéité des trois modèles majoritaires de financement participatif étudiés (don/contrepartie, prêt et capital), un effort collectif est fait pour mettre en valeur les points communs et gommer l’hétérogénéité des secteurs concernés (d’un côté le monde de la création culturelle, de l’autre le monde de la finance). Les plateformes, en tant que dispositifs socio-techniques, cherchent à se présenter comme des instruments neutres qui favoriseraient un appariement naturel entre des demandeurs de fonds et des financeurs. Cette recherche montre au contraire que l’essor de ce modèle de financement est le fruit d’un travail marchand mené par les professionnels du secteur pour recruter deux types d’usagers sur leur plateforme : des demandeurs de fonds d’un côté et des financeurs de l’autre. L’enquête montre les arbitrages opérés par les plateformes entre une logique de volume et une logique de qualité. Pour réduire le risque, les plateformes mettent en place des systèmes de qualification et de sélection des projets, souvent importés de la finance traditionnelle, qui entrent en contradiction avec les discours de démocratisation de l’accès au financement. Dans leurs efforts de développement, elles cherchent aussi à nouer des relations avec les acteurs traditionnels du monde de la finance. Ce faisant elles réintroduisent de nouveaux intermédiaires qui viennent complexifier la relation entre demandeurs de fonds et financeursSince the end of the 2000s, crowdfunding platforms have been developing in France with the promise of a direct and disintermediated relationship between project owners and funders, facilitating access to funds for project owners and allowing French Internet users to fund projects of their choice. This PhD dissertation studies this phenomenon by combining ethnographic observation and interviews with various actors who have participated in the development of this activity. The research shows that the institutionalization of crowdfunding in France stems from a collective action involving industry professionals, representatives of public authorities, platform partners, and the media. While platforms defend a model of self-organization and autonomy, it appears that their development would not have been possible without the intervention of public authorities, who have created a favorable legal framework to crowdfunding, in order to change the relationship of the French population with its savings and to encourage the contribution to the economic health of new firms in a context of crisis. The study also shows that, despite the extreme heterogeneity of the three majority crowdfunding models studied (reward-based, lending-based, and equity-based), there is a collective effort to highlight common characteristics and to blur the heterogeneity of the sectors (on the one hand the world of cultural creation, on the other the world of finance). Platforms, as socio-technical devices, seek to present themselves as neutral instruments that favor a natural match between fund seekers and funders. This research shows that actually the growth of this financing model is the result of a market labor carried out by professionals in the sector to bring two types of users on their platform: the fund-seekers on one side and the funders on the other. The research also shows that the platforms strategic decisions try to balance out quantity and quality of projects. To reduce risks, platforms put in place qualification and project selection processes, often imported from traditional finance - contradicting the idea of democratization of access to funding. In their development efforts, they also seek to build relationships with traditional players from the world of finance. In doing so, they reintroduce new intermediaries that complicate the relationship between fund-seekers and funders
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Zareh, Bannad Kouki Mehrdad. „Development of a novel numerical platform for the assessment of atherosclerotic plaque vulnerability“. Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/57028.
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It is well known that mechanics of atherosclerotic plaques significantly depend on plaque geometry, location, composition, and loading conditions. Computational studies have shown great potential to characterize this mechanical behavior. Different types of plaque morphologies and mechanical properties have been used in two-dimensional (2D) and three-dimensional (3D) computational platforms mostly based on the finite element method to estimate the stability of rupture-prone plaques and detect their locations.
It is well-known that 2D models are not reliable as they do not provide a consistent assessment on the vulnerability of plaques and are highly erroneous. 3D models offer a more effective evaluation but creating 3D models to be further assessed by computational means such as the finite element method is time-consuming. However, 2D models are easier to develop and are less time-consuming to assess. In this thesis, a novel computational platform was developed by which the plaque vulnerability is assessed using only 2D plaque models. We develop idealistic 2D models and their corresponding idealistic 3D models. The idealistic 3D models resemble the worst- and best- case scenarios for each 2D model. Using these 3D idealistic models, a standard error (SE) is estimated and then added to the peak stress values calculated earlier using 2D models. These SEs are also used to assess the probability of plaque stability. In this platform, the effect of viscoelasticity and anisotropy of the plaque composition is taken into consideration and the transmural pressure considered is similar to that of physiological conditions. Also, for the first time heart rate (HR) was introduced as a major predictor of vulnerable plaque ruptures that should be taken into account while mechanics of plaques is studied. A tunable viscoelastic constitutive material model was developed for the fibrous cap tissue in order to calculate the peak cap stress (PCS) in normal physiological conditions while HR changes from 60 bpm to 150 bpm. A critical discussion on stress distribution in the fibrous cap area is made with respect to HR. Results strongly suggest the viscoelastic properties of the fibrous cap tissue and HR together play a major role in the estimation of the PCS values. The results obtained in this thesis may provide a better understanding of the mechanics of atherosclerosis.Applied Science, Faculty of
Engineering, School of (Okanagan)
Graduate
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Nguyen, Thi Minh Tuyen. „Taking architecture and compiler into account in formal proofs of numerical programs“. Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00710193.
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On some recently developed architectures, a numerical program may give different answers depending on the execution hardware and the compilation. These discrepancies of the results come from the fact that each floating-point computation is calculated with different precisions. The goal of this thesis is to formally prove properties about numerical programs while taking the architecture and the compiler into account. In order to do that, we propose two different approaches. The first approach is to prove properties of floating-point programs that are true for multiple architectures and compilers. This approach states the rounding error of each floating-point computation whatever the environment and the compiler choices. It is implemented in the Frama-C platform for static analysis of C code. The second approach is to prove behavioral properties of numerical programs by analyzing their compiled assembly code. We focus on the issues and traps that may arise on floating-point computations. Direct analysis of the assembly code allows us to take into account architecture- or compiler-dependent features such as the possible use of extended precision registers. It is implemented above the Why platform for deductive verification
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Tchorowski, Leo A. „Sparse-Constrained Equivalent Element Distribution Method to Represent Measured Antenna Data in Numerical Electromagnetics Codes“. The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1582877220383629.
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Giovacchini, Valentina <1992>. „Development of a numerical platform for the modeling and optimal control of liquid metal flows“. Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amsdottorato.unibo.it/10269/1/tesi_phd_giovacchini.pdf.
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The main purpose of this work is to develop a numerical platform for the turbulence modeling and optimal control of liquid metal flows.
Thanks to their interesting thermal properties, liquid metals are widely studied as coolants for heat transfer applications in the nuclear context. However, due to their low Prandtl numbers, the standard turbulence models commonly used for coolants as air or water are inadequate.
Advanced turbulence models able to capture the anisotropy in the flow and heat transfer are then necessary. In this thesis, a new anisotropic four-parameter turbulence model is presented and validated. The proposed model is based on explicit algebraic models and solves four additional transport equations for dynamical and thermal turbulent variables. For the validation of the model, several flow configurations are considered for different Reynolds and Prandtl numbers, namely fully developed flows in a plane channel and cylindrical pipe, and forced and mixed convection in a backward-facing step geometry.
Since buoyancy effects cannot be neglected in liquid metals-cooled fast reactors, the second aim of this work is to provide mathematical and numerical tools for the simulation and optimization of liquid metals in mixed and natural convection. Optimal control problems for turbulent buoyant flows are studied and analyzed with the Lagrange multipliers method. Numerical algorithms for optimal control problems are integrated into the numerical platform and several simulations are performed to show the robustness, consistency, and feasibility of the method.
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Erdin, Enes. „Performance Of Parallel Decodable Turob And Repeat-accumulate Codes Implemented On An Fpga Platform“. Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/2/12610998/index.pdf.
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In this thesis, we discuss the implementation of a low latency decoding algorithm
for turbo codes and repeat accumulate codes and compare the implementation results
in terms of maximum available clock speed, resource consumption, error correction
performance, and the data (information bit) rate. In order to decrease the latency a
parallelized decoder structure is introduced for these mentioned codes and the results
are obtained by implementing the decoders on a field programmable gate array. The
memory collision problem is avoided by using collision-free interleavers. Through
a proposed quantization scheme and normalization approximations, computational
issues are handled for overcoming the overflow and underflow issues in a fixed point
arithmetic. Also, the effect of different implementation styles are observed.
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Wang, Zhengquan. „A Hybrid Pseudodynamic Testing Platform for Structural Engineering Research – Application for the Development of an Innovative Retrofit Scheme“. Cincinnati, Ohio University of Cincinnati, 2007. http://www.ohiolink.edu/etd/view.cgi?ucin1178625931.
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Thesis (Ph.D.)--University of Cincinnati, 2007.Title from electronic thesis title page (viewed July 10, 2007). Includes abstract. Keywords: Pseudodynamic Testing; Pre-testing Simulation; Implicit Numerical Method; Special Braced Buildings; Buckling-Enhanced Braces Includes bibliographical references.
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Ming, Lu. „A numerical platform for the identification of dynamic non-linear constitutive laws using multiple impact tests : application to metal forming and machining“. Phd thesis, Toulouse, INPT, 2018. http://oatao.univ-toulouse.fr/20112/1/MING_Lu.pdf.
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The main concern of this thesis is to propose a new inverse identification procedure applied to metal forming and machining situations, which can provide an appropriate parameters set for any elastoplastic constitutive law following J_{2} plasticity and isotropic hardening, by evaluating the correlation between the experimental and numerical responses. Firstly the identification program has been developed, which combines the Levenberg-Marquardt algorithm and the Data processing methods to optimize the constitutive parameters. In terms of experimentation, dynamic compression and tensile tests have been conducted. The final deformed shape of specimens, which relies on a post-mortem analysis, has been selected as the observation quantity. As for the numerical simulation, the numerical models of the same experimental procedure have been built with the finite element software Abaqus/Explicit in order to provide numerical responses. A numerical algorithm has been proposed for the implementation of user defined elastoplastic constitutive laws in Abaqus/Explicit.
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Luddeni, Giovanni. „Improvement of a simulation platform for Helicon Plasma Thrusters: analysis of the boundary conditions and modelling of the sheath“. Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/24296/.
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The proper treatment of the boundary conditions when dealing with fluid simulations of plasma processes constitutes a non-negligible issue that might affect the results, especially when dealing with plasma sources for propulsion applications, e.g., as in Helicon Plasma Thrusters (HPT). In this work, we handle the problem of boundary conditions modelling. Firstly, we have reviewed several established physical models to assess how to properly treat the HPTs. Then, three approaches to account for the sheath have been considered, namely, I) the direct solution of the sheath region through the finite volume discretization, II) the modelling of the sheath through analytical solutions, and III) a hybrid approach in which we coupled two distinguished solvers that handle respectively the bulk region of the plasma and the sheath.
The bulk region solver is based on the classical multi-fluid approach. The sheath is solved either by a fluid or a Lagrangian approach, to account for deviations from the Maxwellian velocity distribution function for each species present in the plasma. The proposed approaches have been tested in terms of plasma profiles (e.g., density) against the experimental case of a Piglet reactor. Generally, all three approaches have given a satisfactory agreement with the experimental measurements. In particular, the first and third approaches have shown similar results, with the latter being assessed with the fluid approach only. As for the computational cost, both methods required similar computation time. Regarding the second approach, the results under-estimate the plasma density if compared to the other methods. Nonetheless, this approach required 97% less computational effort. Ultimately, the hybrid approach achieved good results and it offers interesting possibilities of further development, some of which have been discussed.
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Vaze, Shilpa Arun. „Integrated formulation-solution-design scheme for nonlinear multidisciplinary systems using the MIXEDMODELS platform“. Diss., Manhattan, Kan. : Kansas State University, 2007. http://hdl.handle.net/2097/407.
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Tedesco, Giacomo. „"Offshore tower or platform foundations: numerical analysis of a laterally loaded single pile or pile group in soft clay and analysis of actions on a jacket structure"“. Master's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/6802/.
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Laterally loaded piles are a typical situation for a large number of cases in which deep foundations are used. Dissertation herein reported, is a focus upon the numerical simulation of laterally loaded piles. In the first chapter the best model settings are largely discussed, so a clear idea about the effects of interface adoption, model dimension, refinement cluster and mesh coarseness is reached. At a second stage, there are three distinct parametric analyses, in which the model response sensibility is studied for variation of interface reduction factor, Eps50 and tensile cut-off. In addition, the adoption of an advanced soil model is analysed (NGI-ADP). This was done in order to use the complex behaviour (different undrained shear strengths are involved) that governs the resisting process of clay under short time static loads. Once set a definitive model, a series of analyses has been carried out with the objective of defining the resistance-deflection (P-y) curves for Plaxis3D (2013) data. Major results of a large number of comparisons made with curves from API (America Petroleum Institute) recommendation are that the empirical curves have almost the same ultimate resistance but a bigger initial stiffness. In the second part of the thesis a simplified structural preliminary design of a jacket structure has been carried out to evaluate the environmental forces that act on it and on its piles foundation. Finally, pile lateral response is studied using the empirical curves.
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Rahiman, Tariq Iqbal Hamid. „Neotectonics, Seismic and Tsunami Hazards, Viti Levu, Fiji“. Thesis, University of Canterbury. Geological Sciences, 2006. http://hdl.handle.net/10092/1110.
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Viti Levu, the main island of Fiji, is located in a seismically active area within the Fiji Platform - a remnant island arc that lies in a diffuse plate boundary zone between the Pacific and Australian tectonic plates in the southwest Pacific. The southeast coast of Viti Levu is a highly developed and populated part of Fiji and is vulnerable to the effects of large earthquakes that are expected to occur both onshore and offshore. The structural framework and the origin of seismicity within the Fiji Platform, as well as the seismic and tsunami hazards of central and southeast Viti Levu are investigated. The upper crust of southeast Viti Levu is dissected by several intersecting fault/lineament zones. These are mapped from remote sensing imagery of the surface (topography, radar, and aerial photos) and of the basement (magnetic), and have been subject to rigorous statistical tests of reproducibility and verification with field mapped fault data. Lineaments on the various imagery correlate with faults mapped in the field and show spatial continuity between and beyond mapped faults, thereby providing a fuller coverage of regional structural patterns than previously known. Some fault/lineament zones extend beyond the coastline to the offshore area of southeast Viti Levu. Here high resolution SeaBAT 8160 multibeam bathymetry data and seismic reflection data show that the fault zones occur along, and exert control on the locations of a number of linear submarine canyons. The morpho-structural expression of these canyons are contiguous with fault controlled physiographic features mapped on the nearshore marginal shelf (rectilinear bays and peninsulas, reef passages) and on land (fault valleys, slope and drainage alignments forming lineaments). The canyons are considered to have developed from several cycles of downslope incising and infilling events, whilst their positions were still primarily controlled by zones of weakness created by the fault zones. The principal fault sets in southeast Viti Levu represent generations of regional tectonic faulting that pervaded the Fiji Platform during and after disruption of the proto Fijian arc in the Middle to Late Miocene. These fault sets combine to form a complex network of interlocking faults creating a fault mesh that divides the upper crust into a number of fault blocks ranging from ~2 to 30 km. It is inferred that the fault mesh evolved throughout the Neogene as a response to the anticlockwise rotation of the Fiji Platform through progressive development of different fault sets and intervening crustal block rotations. Regional tectonic deformation is presently accommodated in a distributed manner through the entire fault mesh. Low magnitude earthquakes (
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Tendil, Anthony. „Contrôles tectoniques, climatiques et paléogéographiques sur l'architecture stratigraphique de la plateforme carbonatée urgonienne provençale (France) : approches sédimentologiques, géochimiques et numériques intégrées“. Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0230.
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Les systèmes carbonatés, anciens et actuels, se retrouvent au coeur d’enjeux économiques et sociétaux majeurs, notamment dans le domaine énergétique où ils représentent une part considérable des réserves prouvées de gaz et de pétrole. La présente thèse se focalise sur la plate-forme urgonienne Provençale (Barrémien supérieur–Aptien inférieur), analogue d’affleurement prouvé de réservoirs carbonatés du Moyen-Orient. Près d’une trentaine de coupes stratigraphiques, incluant notamment deux forages réalisés dans le cadre de ce travail, ont été considérées sur l’ensemble du domaine Provençal. La reconnaissance de surfaces d’émersion et d’ennoiement contraintes biostratigraphiquement permet d’appréhender régionalement l’évolution paléogéographique et l’architecture stratigraphique. Plusieurs phases de progradation en direction des bassins adjacents, entrecoupées d’épisodes de perturbation de la production carbonatée, sont identifiées en Provence. Un scénario stratigraphique comparable est proposé pour les plates-formes urgoniennes du Pourtour Vocontien. En Provence, la compartimentation réservoir de la plate-forme urgonienne est principalement contrôlée par le contexte séquentiel des dépôts qui induit une dualité entre des carbonates cimentés précocement et ceux préservant un certain espace poreux. Les règles géologiques définies dans cette étude 1) servent à la réalisation d’un modèle numérique 3-D destiné aux simulations des écoulements à l’échelle de l’aquifère karstique de Fontaine-de-Vaucluse, dont le débit à l’exutoire est classé au cinquième rang mondial, et 2) aident à la prédiction des hétérogénéités sédimentaires et pétrophysiques des systèmes carbonatésThe analysis of carbonate systems is at the heart of major economic and societal challenges, especially in the energy field since they represent significant oil and gas reserves. The present thesis focuses on the Urgonian Provence platform (upper Barremian–lower Aptian interval) which is considered as a valid outcrop analogue of middle East carbonate reservoirs. About thirty stratigraphic sections, including newly acquired cores, are considered throughout the Provence domain. The recognition of biostratigraphically constrained exposure and drowning surfaces enables us to restore the regional palaeogeographic evolution along with the stratigraphic architecture. Several phases of platform progradation toward the adjacent basins, interrupted by episodes of changes in carbonate production, are identified in Provence. A comparable stratigraphic scenario is proposed for the peri-Vocontian Urgonian platforms. In Provence, the reservoir compartmentalisation of the Urgonian platform is mainly controlled by the sequence stratigraphic context that induced a distinction between early cemented carbonates and those preserving part of their original porosity. The geological rules provided in this study 1) are implemented into a 3-D numerical model intended for fluid-flow simulations at the scale of the Fontaine-de-Vaucluse karstic aquifer, whose karst spring is the fifth largest in the world, and 2) help in predicting the sedimentary and petrophysical heterogeneities of carbonate systems
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Moreno, Moreno Flavio David. „Reconocimiento de gestos corporales, utilizando procesamiento digital de imágenes para activar sistema de alarma“. Bachelor's thesis, Universidad Ricardo Palma, 2015. http://cybertesis.urp.edu.pe/handle/urp/1283.
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La investigación realizada a los sistemas de seguridad electrónica de edificios, plantea como objetivo principal el reconocimiento de tres gestos de un lenguaje corporal del personal de vigilancia, y la consecuente activación de alarma en forma automática. Inicialmente se realizó una encuesta dirigida a las administraciones y personal de edificios, para saber cuales eran las ocurrencias que vulneraban la seguridad de un edificio multifamiliar, luego se observaron y analizaron las imágenes capturadas por una cámara de vigilancia ubicada en la recepción, identificando las ocurrencias más vulnerables y gestos asociados a dichos eventos; se seleccionaron tres gestos que en forma inconsciente realizaba el personal de vigilancia ante dichas situaciones. A determinados cuadros que comprenden estas imágenes se le aplicaron técnicas de procesamiento espacial, con ayuda de una iluminación artificial que era más intensa en la parte posterior del sujeto de análisis, consiguiéndose la definición de una silueta binarizada en el entorno Matlab, técnicas como selección del plano rojo, plano de bits más significativo, invertir imagen y transformaciones morfológicas tipo cerradura, definieron una silueta que ayudó a desarrollar un algoritmo matemático para generar una señal eléctrica en el puerto serial USB del ordenador, donde se conectó físicamente una plataforma de hardware Arduino que activa la alarma. La elección de esta plataforma se debió a que Matlab cuenta con un grupo de instrucciones para Arduino, con el objetivo de lograr una comunicación sincronizada entre ordenador e interface.
Las técnicas utilizadas reconocieron 62,5% de los eventos descritos en las encuestas realizadas y que no son mencionadas en temas de investigación similar. Para lograr el objetivo fue necesario analizar un cuadro por segundo.
The research poses as their main objective the three gestures recognition of a body language of surveillance personnel and the consequent activation of alarm automatically. It was initially carried out a survey of the administration and the offices of the buildings to know which were the occurrences that violate the security of a multi-family building, then were observed and analyzed images captured by a surveillance camera located in the reception, identifying the most vulnerable occurrences and gestures associated with these events; were selected three gestures that unconsciously performs surveillance personnel before such situations; to certain pictures that comprise these images were applied spatial processing techniques, with the help of an artificial lighting that was more intense in the back of the subject of analysis, getting the definition of a silhouette binarized in the Matlab environment, techniques such as plane selection red, more significant bit plane, to invest an image and convolution close type, defined a silhouette that allowed to develop a mathematical algorithm that generated an electrical signal in USB serial port of the computer, where it is physically connected a hardware platform Arduino that active the alarm.This platform choice is due to the fact that Matlab has a group of instructions for Arduino, achieving an orderly communication between computer and interface.
The techniques used recognized 62.5 % of the events described in the surveys carried out and which aren’t mentioned in similar research topics. To achieve the objective was necessary to analyze a picture per second.
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Beckstein, Pascal. „Methodenentwicklung zur Simulation von Strömungen mit freier Oberfläche unter dem Einfluss elektromagnetischer Wechselfelder“. Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-232474.
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Im Bereich der industriellen Metallurgie und Kristallzüchtung treten bei zahlreichen Anwendungen, wo magnetische Wechselfelder zur induktiven Beeinflussung von leitfähigen Werkstoffen eingesetzt werden, auch Strömungen mit freier Oberfläche auf. Das Anwendungsspektrum reicht dabei vom einfachen Aufschmelzen eines Metalls in einem offenen Tiegel bis hin zur vollständigen Levitation. Auch der sogenannte RGS-Prozess, ein substratbasiertes Kristallisationsverfahren zur Herstellung siliziumbasierter Dünnschichtmaterialien, ist dafür ein Beispiel. Um bei solchen Prozessen die Interaktion von Magnetfeld und Strömung zu untersuchen, ist die numerische Simulationen ein wertvolles Hilfsmittel. Für beliebige dreidimensionale Probleme werden entsprechende Berechnungen bisher durch eine externe Kopplung kommerzieller Programme realisiert, die für Magnetfeld und Strömung jeweils unterschiedliche numerische Techniken nutzen. Diese Vorgehensweise ist jedoch im Allgemeinen mit unnötigem Rechenaufwand verbunden. In dieser Arbeit wird ein neu entwickelter Methodenapparat auf Basis der FVM vorgestellt, mit welchem sich diese Art von Berechnungen effizient durchführen lassen. Mit der Implementierung dieser Methoden in foam-extend, einer erweiterten Version der quelloffenen Software OpenFOAM, ist daraus ein leistungsfähiges Werkzeug in Form einer freien Simulationsplattform entstanden, welches sich durch einen modularen Aufbau leicht erweitern lässt. Mit dieser Plattform wurden in foam-extend auch erstmalig dreidimensionale Induktionsprozesse im Frequenzraum gelöst.
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De, Candia SM. „Experimental and numerical investigations into the underwater explosion induced whipping response of submerged platforms“. Thesis, 2019. https://eprints.utas.edu.au/31703/1/De_Candia_whole_thesis.pdf.
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This thesis reports the findings of an experimental and numerical investigation into the whipping response of a submerged platform, due to loading from near-field, non-contact underwater explosion (UNDEX) events.
The experimental investigation examined the whipping response of a generic submerged platform subjected to UNDEX. Eight scenarios were investigated, using different explosive charge sizes, longitudinal, and transverse stand-off locations, to explore the effects of these variables on the platform’s whipping response, and to provide validation data for the numerical investigation. It was found that UNDEX stand-off locations near the anti-node of the first bending mode shape induced the most severe whipping responses, while stand-offs near the node of the first bending mode shape had greatly reduced whipping responses.
A numerical model was developed and validated against the experimental results, using incident pressure and strain measurements. Three numerical studies were conducted with the validated numerical model, investigating the effects of additional stand-off distances at the previously explored longitudinal stand-off locations, the whipping response from an intermediate charge size, and the effects of the UNDEX bubble loading on the whipping response by using a shock-only loading model.
From these studies, the following novel contributions were made:
The stand-off distance was found to only affect the whipping severity while the charge size and stand-off location determined the modal contributions of the whipping response.
A comparison of the peak whipping response to the bubble pressure impulse suggests that three distinct forms of whipping could be induced, and these can be determined by the proximity of the UNDEX stand-off location to the nodes and anti-nodes of the platform’s first bending mode shape. These were classified as critical, resilient, and general whipping responses.
The critical whipping response occurred when the UNDEX stand-off location was near the anti-node of the first bending mode shape. This was characterised by a dominant response of the first bending mode and minimal contribution from other bending modes in the overall response. The severity of this response increased nonlinearly as the bubble impulse increased and when the bubble pulsation frequency was similar to the first bending mode frequency. This is the most severe form of UNDEX induced whipping.
The resilient whipping response occurred when the UNDEX stand-off location was near the node of the first bending mode shape. This was characterised by minimal contribution of the first bending mode compared to others in the overall response. From these scenarios, the bubble loading had minimal effect on the whipping response. This was confirmed from good correlation in comparisons of the strain responses from experimental measurements and the results from the numerical shock-only loading study. This is the least severe form of UNDEX induced whipping and the most desirable outcome from an unavoidable UNDEX threat.
The general whipping response occurred when the UNDEX stand-off location was between the nodes and anti-nodes of the first bending mode shape. This was characterised by similar contributions of multiple bending mode responses in the overall response. The severity from this response increased linearly for increases in the bubble impulse. It is suggested this is the most likely form of UNDEX induced whipping to occur, based on the large number of variables involved with UNDEX loading and platform response scenarios.
Current analysis methodologies are able to identify the resilient whipping response but some methods that focus on the shock response of a platform may not identify the critical and general whipping responses. This was demonstrated by comparison of the experimental measurements to a numerical shock-only loading models for the most severe UNDEX scenarios, where shock-only loading and response assumptions under-predicted the whipping response by 39 % and 54 % for the critical and general whipping responses respectively.
The relative increase in the severity of the whipping response from a reduction in the stand-off distance was consistent for all similar forms of whipping. This suggests that the whipping severity from many different stand-off distances can be approximated through analysis of only a few scenarios at different stand-off locations on a specific naval platform. It is suggested that this knowledge may allow a rapid assessment tool to be developed that could determine a platform’s survivability from a wide variety of UNDEX scenarios.
The trends from each form of whipping severity compared to bubble pressure impulse were examined with limited extrapolation. This suggested that four whipping response analysis regimes exist: far-field elastic, near-field and non-contact elastic, non-contact plastic, and contact damage. Exact limits of these regimes were not identified, and all are promising areas for further investigation.
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Pereira, David dos Santos. „Numerical modeling of extrusion forming tools: improving its efficiency on heterogeneous parallel computers“. Master's thesis, 2014. http://hdl.handle.net/1822/36701.
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Dissertação de mestrado em Engenharia InformáticaPolymer processing usually requires several experimentation and calibration attempts to lead to a final result with the desired quality. As this results in large costs, software applications have been developed aiming to replace laboratory experimentation by computer based simulations and hence lower these costs. The focus of this dissertation was on one of these applications, the FlowCode, an application which helps the design of extrusion forming tools, applied to plastics processing or in the processing of other fluids. The original application had two versions of the code, one to run in a single-core CPU and the other for NVIDIA GPU devices. With the increasing use of heterogeneous platforms, many applications can now benefit and leverage the computational power of these platforms. As this requires some expertise, mostly to schedule tasks/functions and transfer the necessary data to the devices, several frameworks were developed to aid the development - with StarPU being the one with more international relevance, although other ones are emerging such as Dynamic Irregular Computing Environment (DICE). The main objectives of this dissertation were to improve the FlowCode, and to assess the use of one framework to develop an efficient heterogeneous version. Only the CPU version of the code was improved, by first applying techniques to the sequential version and parallelizing it afterwards using OpenMP on both multi-core CPU devices (Intel Xeon 12-core) and on many-core devices (Intel Xeon Phi 61-core). For the heterogeneous version, StarPU was chosen after studying both StarPU and DICE frameworks. Results show the parallel CPU version to be faster than the GPU one, for all input datasets. The GPU code is far from being efficient, requiring several improvements, so comparing the devices with each other would not be fair. The Xeon Phi version proves to be the faster one when no framework is used. For the StarPU version, several schedulers were tested to evaluate the faster one, leading to the most efficient to solve our problem. Executing the code on two GPU devices is 1.7 times faster than when executing the GPU version without the framework. Adding the CPU to the GPUs of the testing environment do not improve execution time with most schedulers due to the lack of available parallelism in the application. Globally, the StarPU version is the faster one followed by the Xeon Phi, CPU and GPU versions.
O processamento de polímeros requer normalmente várias tentativas de experimentação e calibração de modo a que o resultado final tenha a qualidade pretendida. Como isto resulta em custos elevados, diversas aplicações foram desenvolvidas para substituir a parte de experimentação laboratorial por simulações por computador e consequentemente, reduzir esses custos. Este dissertação foca-se numa dessas aplicações, o FlowCode, uma aplicação de ajuda à conceção de ferramentas de extrusão aplicada no processamento de plásticos ou no processamento de outros tipos de fluidos. Esta aplicação inicial era composta por duas versões, uma executada sequencialmente num processador e outra executada em aceleradores computacionais NVIDIA GPU. Com o aumento da utilização de plataformas heterogéneas, muitas aplicações podem beneficiar do poder computacional destas plataformas. Como isto requer alguma experiência, principalmente para escalonar tarefas/funções e transferir os dados necessários para os aceleradores, várias frameworks foram desenvolvidas para ajudar ao desenvolvimento - sendo StarPU a framework com mais relevância internacional, embora outras estejam a surgir como a framework DICE. Os principais objetivos desta dissertação eram melhorar o FlowCode assim como avaliar a utilização de uma framework para desenvolver uma versão heterogénea eficiente. Apenas a versão CPU foi melhorada, primeiro aplicando técnicas na versão sequencial, e depois procedendo à paralelização usando OpenMP em CPUs multi-core (Intel Xeon 12-core) e aceleradores many-core (Intel Xeon Phi 61-core). Para a versão heterogénea, foi escolhido a framework StarPU depois de se ter feito um estudo das frameworks StarPU e DICE. Os resultados mostram que a versão CPU paralela é mais rápida que a GPU em todos os casos testados. O código GPU está longe de ser eficiente, necessitando diversas melhorias. Portanto, uma comparação entre CPUs, GPUs e Xeon Phi’s não seria justa. A versão Xeon Phi revela-se ser a mais rápida quando não é usada nenhuma framework. Para a versão StarPU, vários escalonadores foram testados para avaliar o mais rápido, levando ao mais eficiente para resolver o nosso problema. Executar o código em dois GPUs é 1.7 vezes mais rápido do que executar para um GPU sem framework em um dos casos testados. Adicionar o CPU aos GPUs do ambiente de teste não melhora o tempo de execução para a maioria dos escalonadores devido à falta de paralelismo disponível. Globalmente, a versão StarPU é a mais rápida seguida das versões Xeon Phi, CPU, e GPU.
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Yu, Chia-Hung, und 游家鋐. „Numerical Testing Platform for Small Size Horizontal Axis Wind Turbines“. Thesis, 2010. http://ndltd.ncl.edu.tw/handle/40679089577648859043.
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碩士清雲科技大學
電機工程研究所
98
A numerical simulation model has been developed to be a testing platform for small size horizontal axis wind turbines (HAWTs). The simulation model is created for promoting the blade design and the full set performance of a 250W HAWT with six blades. One computational fluid dynamics (CFD) software is applied to build up the system. A three-dimensional simulation space is used to describe interactions between the fluid and the rotating device. In order to decrease the total number of grids and computation loading, multi-region and non-structural meshing method is applied in this model. Distributions of the blade static torques for different rotating angles under different mesh sizes are examined to find the optimal grid meshing. It helps us to ensure the results are trustable. Dynamic simulations for free rotation are performed under the input wind speed of 10m/s. The rotating speeds and torques on the blades in numerical results agree well with the experimental measurements performed in the wind tunnel of Ching Yun University. It indicates this numerical model can be a powerful platform to examine new design or modification of the blades.
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Chen, Yu-Wen, und 陳宇文. „The Development of Novel Numerical Simulation Platform - Adaptive Computation Framework“. Thesis, 2010. http://ndltd.ncl.edu.tw/handle/83105377812606434587.
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博士國立交通大學
土木工程系所
98
This study proposed a innovative methodology for developing numerical simulation models that overwhelm conventional developing process and greatly increase the efficiency of model development. The advancement of information technology (IT) have significantly improved the computational capa- bility of numerical model, thus increased the importance of numerical simulation in various engineering analysis. The conventional process of numerical model development consists four steps that includes “conceptual model description”, “mathematical model definition”, “numerical model derivation” and “computer program development”. Once a numerical model has developed, one still has to repeat the four steps to modify the code even if only part of the original problem was modified with the conven- tional model developing process. The modification process is always complicated and time consuming. Hence, the traditional development process is lack of flexibility and difficult to update the computing functionalities of an existed numerical model. Therefore, to resolve these model developing issues, the Adaptive Computation Framework (ACF), a novel methodology to develop numerical simulation method, is proposed in this study. By using the proposed ACF method, a new computing function is easy to add into a existing model, i.e. a numerical model can grow with new computing functions. The ACF is much more than just a new numerical scheme such as the finite element (FEM) or finite difference method (FDM). At the “mathematical model definition” step, the ACF define a problem by the set of originally fundamental equations without further artificial combination and simplification to get a more compact set of PDEs. An ”equation consistence analysis” is proposed in this step to ensure the consistence of these fundamental equations and variables, and also determine the sequence to solve the equations. In the “numerical model derivation” step, instead of applying complicated numerical scheme such as FEM or FDM, only simple difference method is needed to discretize the equations and the “Voronoi Diagram” is proposed as the griding method for spatial discretization. In the “computation program development” step, instead of solving a matrix equation, a general iteration method consists of inner and outer iteration is proposed to compute the solutions at each grids. To demo the effectivity of the proposed methodology, three different groundwater numerical mod- els, “groundwater flow only”, “groundwater flow with heat transport” and “groundwater flow with head and solute transport”, are developed by using ACF. Five different cases are examined to ver- ify the correctness and the flexibility of ACF. The cases studies demonstrated that, using the ACF method, a model computing functions can be extended by only adding the required equations and thus increase the model computing capability with minimum coding effort. By using the ACF, engineers or scientists can get relief from the time consuming model redeveloping process, thus can focus more on the problem analysis instead of tool (model) development.
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Clayton, DK. „Blast survivability of a fatigued naval surface platform“. Thesis, 2022. https://eprints.utas.edu.au/47501/1/Clayton_whole_thesis_ex_pub_mat.pdf.
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An assessment of the blast survivability is a requirement of modern naval vessels during both the initial design stage, and when life-of-type extension analyses are undertaken. Changes in the operational profile of naval vessels throughout their service life combined with the use of high strength maritime steels have resulted in structural fatigue becoming an increasingly important consideration as vessels age. Literature suggests that fatigue ageing may impact the high strain-rate performance of a structure. A lack of understanding of the effects of fatigue aging may therefore result in overestimations of the blast survivability of a naval platform, possibly putting sailors’ lives at a greater risk than if the effects could be accounted for.
This PhD thesis aims to investigate and quantify the effect that fatigue has on blast survivability of naval structures made of DH36 steel, a common naval structural steel, by means of experimental and numerical investigations. The experimental methodology was developed and implemented to determine any effect of fatigue ageing on the high strain rate material properties of DH36. The numerical investigation determined the effect of fatigue cracking on structural response to blast loading. Following this, two machine learning tools were developed to enable the consideration of the results of this research in the design and analysis of a vessel.
The novel experimental methodology included the development of a fatigue ageing process for DH-36 specimens from which smaller specimens for high strain rate testing were obtained. These smaller specimens were tested using a bespoke Split Hopkinson Tension Bar setup. The results show that there is no significant change in the high strain rate material properties of fatigued DH36, however a reduction in quasi-static yield stress and flow stress curves is evident.
The numerical investigation was aimed at determining the effects that fatigue cracks may have on the structural response of a representative ship stiffened panel. The novel methodology includes extensive validation of an application of crack propagation elements in LS-DYNA using experimentally obtained explosive bulge tests data. The inbuilt LS-DYNA Friedlander-equation-based load models are utilised to model the blast loading over a wide range of charge sizes, stand-offs, and locations for a variety of crack lengths determined by crack propagation modelling. It was found that, for the investigated stiffened panel, a reduction in the highest survivable charge size of up to 37.5% exists, when compared to the survivable charge size for a crack that is not detectable by eye. This finding suggests that cracks can play a significant role in the structural response to blast loading for ship stiffened panels. The finding displays a need for designers and analysts to account for the effect of cracks on blast survivability.
To assist the design and analysis of the fatigue effect on blast survivability a machine learning tool was developed based on a Neural Network algorithm. The tool allows for the rapid assessment of the charge required to initiate plate failure of a representative stiffened ship panel and is based on inputs of the charge size and location, and the length of fatigue crack that is present in the stiffener. The tool can readily integrate new or extended datasets of blast event results, and once an appropriate dataset is used for training, allows designers to determine the effect of different fatigue crack scenarios on the survivability of a given geometry when a fatigue analysis is incorporated.
Finally, a method to determine the blast survivability of a representative ship stiffened panel is presented. The methodology utilises the results of the numerical investigation into blast loading and fatigue cracks, alongside crack initiation and growth models to determine change in blast survivability over time. The blast survivability of a representative ship stiffened panel is suggested to have been reduced by an average of 9% over a 20-year period due to fatigue crack growth. This is a significant reduction which, if unaccounted for in design and life-of-type extension analyses, will lead to the overestimation of the ability of a vessel to withstand blast loading.
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Chen, Li-Hsien, und 陳立賢. „A Numerical Study of Heavyweight Shipboard Equipment Shock Resistant Using Floating Shock Platform“. Thesis, 2008. http://ndltd.ncl.edu.tw/handle/62503641949647761196.
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碩士大葉大學
機械工程研究所碩士班
96
The Navy’s shock test standard MIL-STD-901D requires that heavyweight equipment above a designated weight must be tested on a floating shock platform(FSP) barge, but the shock test is time-consuming, laborious and spend money. And the finite element modeling and simulation can provide a viable, cost effective alternative to shock tests. Underwater explosion shock response analysis of a MIL-STD-901D standard floating shock platform(SFSP) was performed using nonlinear finite element software accuracy of analysis results was examined with the existing test results in this paper at first. The objective of this study was to examine the response of different weight in different equipment and difference from the explosion at the depth of explosives, when subjected to an underwater explosion, utilizing the ABAQUS software. Three heavyweight equipments 9000lbs, 18400lbs, and 35800lbs are studied in the five stand off of explosive points: 20ft, 30ft, 40ft, 60ft, and 80ft, and two explosive depths: 20ft, and 30ft. And then compared with the U.S.H.I. TEST laboratory’s test data and Kwon’s LS-DYNA/USA simulations to demonstrate the feasibility of the ABAQUS/USA. Finally, when the heavyweight equipments are setted NavySeamountTM250 shock mount, the numerical results showed that the shock effect of vertical direction can be reduced 15%, the transverse direction can be reduced 5% to 10%, but there was only 5% reduction at fore and aft the bow to the stern while no apparent effect. This paper established the floating shock platform finite element model and showed the benefits that installed shock mounts on heavy weight equipments. These results can provide a reference for correlative organizations to analize the shock effect.
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Shih-HsunHung und 洪仕勳. „Numerical Simulation of Optically-induced Dielectrophoresis Platform and Its Application on Manipulation of Emulsion Droplets“. Thesis, 2011. http://ndltd.ncl.edu.tw/handle/31868315631269173475.
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黎光祥. „An Investigation of Numerial and Analytical Methods for the Forward Kinematic Analysis of the Stewart Platform“. Thesis, 1997. http://ndltd.ncl.edu.tw/handle/45315255309173321440.
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碩士國立成功大學
機械工程學系
85
An Investigation of Numerical and Analytical Methods for the Forward Kinematic Analysis of the Stewart Platform The general Stewart Platform mechanism (SPM) is a fully parallel mechanism that has been used in various applications. The forward and inverse kinematic analyses of the SPM are essential when using the mechanism. The inverse kinematic analysis is straightforward; however, the forward kinematic analysis results in complicated equations and requires tedious operations. Raghavan(1993) utilized the numerical continuation method to solve the forward kinematic problem and showed that a general SPM had 40 configurations. Husty(1996) confirmed Raghavan''s conclusion by using an analytic approach. Unfortunately, the polynomial system introduced by Raghavan was complicated, and it traced too many unnecessary homotopy paths. The analytic approach introduced by Husty was not easy to implement due to the complexity of the symbolic manipulation of equations. This thesis first investigates the polynomial continuation method and implements it by writing a computer program to perform simulations. We then study how the spatial kinematic mapping method is applied to this problem and write a symbolic manipulation program to drive the equations. Finally, this thesis proposes another approach. By using the polynomial system in Soma space, we introduce a continuation method that traces less paths. We significantly reduce unnecessary homotopy paths and avoid tedious symbolic elimination processes. A numerical example of the general SPM is given in this thesis. Using the purposed method, we have successfully found 80 finite roots, of which only 40 roots lead to different transformation matrices. Therefore, we obtain 40 different configurations of the general SPM, which confirms previous research results.
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Silva, Ramon Alejandro. „Numerical Simulation and Laboratory Testing of Time-Frequency MUSIC Beamforming for Identifying Continuous and Impulsive Ground Targets from a Mobile Aerial Platform“. Thesis, 2013. http://hdl.handle.net/1969.1/149539.
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When a microphone array is mounted on a mobile aerial platform, such as an unmanned aerial vehicle (UAV), most existing beamforming methods cannot be used to adequately identify continuous and impulsive ground. Here, numerical simulation results and laboratory experiments are presented that validate a proposed time-frequency beamforming method based on the Multiple Signal Classification (MUSIC) algorithm to detect these acoustic sources from a mobile aerial platform.
In the numerical simulations three parameters were varied to test the proposed algorithm’s location estimation performance: 1) the acoustic excitation types; 2) the moving receiver’s simulated flight conditions; and 3) the number of acoustic sources. Also, a distance and angle error analysis was done to quantify the proposed algorithm’s source location estimation accuracy when considering microphone positioning uncertainty. For experimental validation, three laboratory experiments were conducted. Source location estimations were done for: a 600 Hz sine source, a banded white noise source between 700-800 Hz, and a composite source combined simultaneously with both the sine and banded white noise sources.
The proposed algorithm accurately estimates the simulated monopole’s location coordinates no matter the excitation type or simulated trajectory. When considering simultaneously-excited, multiple monopoles at high altitudes, e.g. 50 m, the proposed algorithm had no error when estimating the source’s locations. Finally, a distance and angle error analysis exposed how relatively small microphone location error, e.g. 1 cm maximum error, can propagate into large averaged distance error of about 10 m in the far-field for all monopole excitation types. For all simulations, however, the averaged absolute angle error remained small, e.g. less than 4 degrees, even when considering a 5 cm maximum microphone location error.
For the laboratory experiments, the sine source had averaged distance and absolute angle errors of 0.9 m and 14.07 degrees from the source’s true location, respectively. Similarly, the banded white noise source’s averaged distance and absolute angle errors were 1.9 m and 47.14 degrees; and lastly, the averaged distance and absolute angle errors of 0.78 m and 8.14 degrees resulted when both the sources were simultaneously excited.
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Caetano, Sandrina de Fátima Rodrigues. „Modelação numérica de uma solução de reforço de solos para fundações de aerogeradores“. Master's thesis, 2015. http://hdl.handle.net/1822/40648.
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Dissertação de mestrado integrado em Engenharia CivilSempre que uma torre eólica é construída sobre um terreno com baixas características mecânicas, esta é tradicionalmente fundada numa rede de estacas encastradas numa sapata circular. A implementação de inclusões rígidas no solo tem vindo a substituir as tradicionais estacas em alguns tipos de obras. O reforço de solos moles com inclusões rígidas verticais é uma técnica que envolve uma rede de inclusões introduzidas no solo e uma camada usualmente constituída por material granular, posicionada entre o solo melhorado e a estrutura. Nesta camada são desenvolvidos arcos que transferem praticamente todas as cargas diretamente para as inclusões, permitindo a redução e a homogeneização dos assentamentos à superfície do maciço reforçado. O reforço pode ser completado com a introdução de um geossintético na base da plataforma de transferência de carga, adicionando ao sistema um novo efeito que permite aumentar ainda mais a transferência da carga para as inclusões. Esta técnica tem-se aplicado nas diversas tipologias de estruturas, desde aterros de estradas ou ferrovias, zonas industriais, reservatórios… O trabalho desta dissertação constitui uma contribuição para a compreensão do comportamento de solos moles reforçados com inclusões rígidas, onde a sapata de uma eólica assenta numa camada de solo, que funciona como plataforma de transferência de carga. Uma análise numérica foi desenvolvida para simular três sistemas de fundação: sapata isolada, fundação por estacas e solo reforçado com inclusões. Deslocamentos e tensões foram avaliados nas três soluções. As estacas e as inclusões apresentaram o comportamento semelhante e para aquele solo em especifico, não se conseguiu avaliar a eficiência da solução. Um estudo paramétrico foi efetuado, fazendo variar o tipo de solo, o número de elementos verticais e o módulo de elasticidade. Um novo modelo foi gerado, à custa da introdução de uma camada granular. Deslocamentos e tensões foram novamente determinados para os vários cenários envolvidos. Esta análise permitiu observar que: i) a técnica das inclusões rígidas tem mais impacto em solos com características inferiores; ii) para um determinado de tipo de solo há uma configuração dos elementos mais eficaz, sendo que, a partir daí não se torna vantajoso aumentar o número de elementos rígidos.
Whenever a wind tower is built on a soil with low mechanical properties, traditionally the foundation system is composed by a network of piles in a circular foundation. The implementation of rigid inclusions in the soil has been replacing the traditional piles on some types of construction. The reinforcement of the soft soil with vertical rigid inclusions is a technique that involves a network of inclusions introduced into the soil and a layer usually comprised by granular material, positioned between the ground and structure. On this layer are developed arcs transferring almost all loads directly to the inclusions, allowing the reduction and homogenisation of the settlements on the surface of the reinforced soil. The reinforcement may be supplemented by the introduction of a geosynthetic placed under the load transfer platform, adding to the system a new effect which allows to further increase the load transfer to the inclusions. This technique has been implemented in various types of structures, from landfill roads or railways, industrial areas, reservoirs ... The work developed in the scope of this thesis is a contribution to the understanding of the behavior of soft soils reinforced with rigid inclusions, where a wind tower foundation rests on granular medium, which functions as a load transfer platform. A numerical analysis was developed to simulate three foundation systems: isolated foundation, piles foundation and reinforced soil with rigid inclusions. Displacements and stresses were evaluated for the three solutions. Piles and inclusions presented similar behavior for the specific soil under study. A parametric study was performed by varying the type of soil, the number of vertical elements and the modulus of elasticity. A new model was generated at the expense of introducing a granular layer. Displacements and stresses were again determined for the different scenarios involved. This analysis allowed to observe that: i) the technique of rigid inclusions has more impact on soils with lower geomechanical characteristics; ii) for a determined type of soil there is a more effective configuration of elements, so it is not advantageous to increase the number of rigid elements from a certain value.
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Beckstein, Pascal. „Methodenentwicklung zur Simulation von Strömungen mit freier Oberfläche unter dem Einfluss elektromagnetischer Wechselfelder“. Doctoral thesis, 2017. https://tud.qucosa.de/id/qucosa%3A30749.
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Im Bereich der industriellen Metallurgie und Kristallzüchtung treten bei zahlreichen Anwendungen, wo magnetische Wechselfelder zur induktiven Beeinflussung von leitfähigen Werkstoffen eingesetzt werden, auch Strömungen mit freier Oberfläche auf. Das Anwendungsspektrum reicht dabei vom einfachen Aufschmelzen eines Metalls in einem offenen Tiegel bis hin zur vollständigen Levitation. Auch der sogenannte RGS-Prozess, ein substratbasiertes Kristallisationsverfahren zur Herstellung siliziumbasierter Dünnschichtmaterialien, ist dafür ein Beispiel. Um bei solchen Prozessen die Interaktion von Magnetfeld und Strömung zu untersuchen, ist die numerische Simulationen ein wertvolles Hilfsmittel. Für beliebige dreidimensionale Probleme werden entsprechende Berechnungen bisher durch eine externe Kopplung kommerzieller Programme realisiert, die für Magnetfeld und Strömung jeweils unterschiedliche numerische Techniken nutzen. Diese Vorgehensweise ist jedoch im Allgemeinen mit unnötigem Rechenaufwand verbunden. In dieser Arbeit wird ein neu entwickelter Methodenapparat auf Basis der FVM vorgestellt, mit welchem sich diese Art von Berechnungen effizient durchführen lassen. Mit der Implementierung dieser Methoden in foam-extend, einer erweiterten Version der quelloffenen Software OpenFOAM, ist daraus ein leistungsfähiges Werkzeug in Form einer freien Simulationsplattform entstanden, welches sich durch einen modularen Aufbau leicht erweitern lässt. Mit dieser Plattform wurden in foam-extend auch erstmalig dreidimensionale Induktionsprozesse im Frequenzraum gelöst.