Este trabalho discute a questão da interação entre o casco do navio e o propulsor em funcionamento conjunto, e sua simulação por ferramentas computacionais. O texto se concentra em descrever os principais efeitos dessa interação, as principais dificuldades em se estimar esses efeitos, os métodos tradicionalmente usados, e como ferramentas computacionais podem ser aplicadas de maneira vantajosa. No texto também pode ser encontrada uma análise crítica dos métodos mais comuns e dos resultados, baseada em trabalhos de diversos autores, publicados nacional e internacionalmente. É apresentado o método dos volumes finitos, usado nesta pesquisa, algumas de suas particularidades principais, vantagens e desvantagens, e os resultados das simulações realizadas, interpretados à luz dos valores experimentais usados para comparação e das limitações do método dos Volumes Finitos. A comparação é feita analisando-se grandezas integrais, como a resistência do casco ou o empuxo do propulsor; e também as características do escoamento, como o perfil de velocidade na esteira, presença de vórtices, e outras estruturas típicas. Os resultados obtidos têm a mesma ordem de precisão dos que tem sido obtidos por outros pesquisadores, internacionalmente, e são coerentes qualitativamente; mas algumas questões referentes aos modelos físico e numérico escolhidos ainda limitam a precisão dos resultados e restringem sua adoção em atividades de engenharia. Entretanto, diversas características observadas no escoamento contribuem para aumentar o conhecimento de alguns fenômenos envolvidos no problema. / This work is about the hull and propeller interaction in joint functioning, and its simulation by computational tools. The text concentrates in describing the main effects of such interaction, the main difficulties in the estimation of these effects, the methods traditionally adopted, and how computational tools can be applied in advantageous way. A critical analysis of the most common methods and results, based on paperworks of several different authors worldwide, can also be found. The Finite Volumes method, used in this research, is presented - its main issues, advantages and disadvantages, and the simulations outcomes, compared to the experimental values and explained by the knowledge of the Finite Volumes method limitations. The comparison is made by means of both integral values, such as the hull\'s resistance or the propeller thrust; as well as the characteristics of the flow, like the wake velocity profile, presence of vortex, and other typical structures. The results shows the same error band than the ones which has been obtained by other researchers, worldwide, and most of the typical characteristics of the flow were observed. But some issues concerned to the chosen physical and numerical models still limit the precision of the outcomes, and restrict the application of such models at engineering activities. But several insights about the flow, obtained at this study, can be useful to the understanding of some phenomena involved in the propeller operation.

Apresenta-se um pré-processador para análise de pavimentos de edifícios via método dos elementos finitos desenvolvido como um aplicativo do ambiente Windows. O programa é interativo, permitindo identificar problemas de imediato na criação do modelo a ser estudado. Possui recursos gráficos básicos para a definição geométrica da estrutura. A saída de dados é programável para que o pré-processador não se prenda a um só programa de cálculo. Assim, os mesmos dados de uma estrutura podem ser analisados por diferentes programas de cálculo o que possibilita a escolha do programa mais adequado, dependendo do tipo de análise desejado. O aplicativo tem recursos para definir elementos finitos de barra e placa. Como o número desses elementos normalmente é grande, eles são gerados de uma forma automatizada. / lt is presenting a Windows preprocessar for building slab analysis by Finite Element Method. lt is an interactive program, allowing problems to be identified while the model is generated. It has graphical resources to define the structure. The program output is defined by the user; therefore it is possible to use the preprocessar with many other finite element programs. This allows the engineer to choose the appropriate program depending on the kind of analysis is wanted. The program can define frame and shell finite elements. As slabs usually need large numbers of these elements to be properly analyzed, they are generated using automatic meshing.

The Finite Element Method is a computationally expensive method used to perform engineering analyses. By performing such computations on a parallel machine using a SIMD paradigm, these analyses' run time can be drastically reduced. However, the mapping of the FEM mesh elements to the SIMD machine processing elements is an NP-complete problem. This thesis examines the use of Genetic Algorithms as a search technique to find quality solutions to the mapping problem. A hill climbing algorithm is compared to a traditional genetic algorithm, as well as a "messy" genetic algorithm. The results and comparative advantages of these approaches are discussed.

<p>U disertaciji su razvijeni kolokacioni postupci sa C¹- splajnovima&nbsp;proizvoljnog stepena za re&scaron;avanje singularno-perturbovanih problema&nbsp;reakcije-difuzije u jednoj i dve dimenzije. U 1D, pokazano je da kolokacioni&nbsp;postupak sa kvadratnim C¹-&nbsp;splajnom na modifikovanoj &Scaron;i&scaron;kinovoj mreži,&nbsp;konvergira uniformno, sa redom konvergencije skoro dva. Takođe, na gradiranim mrežama, ovaj metod ima red konvergencije dva &ndash; uniformno do na logaritamski faktor. Aposterirona ocena je postignuta za kolokacione postupke sa C¹- splajnovima proizvoljnog stepena na proizvoljnoj mreži. Ova ocena je iskori&scaron;ćena i za kreiranje adaptivnih mreža. Numerički rezultati povtrđuju dobijene ocene. U 2D su razmatrane kolokacije sa bikvadratnim splajnovima. Aposterirona ocena gre&scaron;ke je postignuta. Numerički rezultati potvrđuju dobijene teorijske rezultate.<br />&nbsp;</p> / <p>Collocations with arbitrary order C¹-splines for a singularly perturbed reaction-diffusion problem in one dimension and two dimensions are studied. In 1D, collocation with quadratic C¹-splines is shown to be almost second order accurate on modified Shishkin mesh in the maximum norm, uniformly in the perturbation parameter. Also, we establish a second-order maximum norm a priori estimate on recursively graded mesh uniformly up to a logarithmic factor in the singular perturbation parameter. A posteriori error bounds are derived for the collocation method with arbitrary order C¹-splines on arbitrary meshes. These bounds are used to drive an adaptivemeshmoving algorithm. An adaptive algorithm is devised&nbsp;to resolve the boundary layers. Numerical results are presented. In 2D, collocation with biquadratic C¹-spline is studied. Robust a posteriori error bounds are derived for the collocation method on arbitrary meshes. Numerical experiments completed our theoretical results.</p>

In this thesis, a numerical method is developed for simulating non-isothermal multiphase flows, which are important in many technical applications such as crystal growth and welding. The method is based on the arbitrary Lagrangian Eulerian method of Li (2013). The interface is represented explicitly by mesh lines, and is tracked by an adaptive moving unstructured mesh. The $P2-P1d$ finite element method (FEM) is used for discretisation and the incompressible Navier-Stokes equations are solved by the uzawa method. Firstly, a thorough study is presented on the method's capability in numerically representing the force balance condition on the interface. An inaccurate representation of this condition induces the non-physical spurious currents, which degrade the simulation accuracy especially when the viscous damping is weak (small Ohnesorge number, $Oh$). For the example of a circular/spherical droplet, the interfacial tension and the associated pressure jump are exactly balanced numerically and thus the static Laplace solution exists in our method. The stability of this solution is examined numerically. The amplitude of the dimensionless spurious currents is found to be around $10^{−15}$ for $Oh \geq 10^{−3} $. Another benchmark test is the axisymmetric oscillation of a freesurface droplet/bubble. The simulation results are in good agreement with the analytical solution for $Oh = 10^{−3}$. This is by far the first successful simulation of droplet/bubble oscillation with such weak viscous damping and it demonstrates the ability of our method in simulating flows with strong capillary forces. Secondly, a numerical treatment of interface topology changes is incorporated into our method for studying problems with interface breakup. Thanks to the adaptive mesh generator, the thin region between the interface boundary and another boundary consists of one layer of elements. The interface topology change is performed once the minimum distance between the two boundaries falls below a pre-set scale $l_{breakup}$ . The numerical implementation is verified through two different examples: dripping faucet and droplet coalescence. Remarkably good agreement has been obtained with the experimental results. The simulation of the low Oh dripping problem shows both the accuracy and robustness of our method. The simulation of droplet coalescence demonstrates the great advantage of our method in solving problems with a large disparity in length scales. Finally, an FEM solver for temperature is developed and the non-isothermal effects are included in our method for the purpose of simulating non-isothermal multiphase flows. The modified method is validated to be accurate through three benchmark examples: natural convection in a cavity, thermocapillary convection of two layers, and droplet migration subject to a temperature gradient. Our method is then applied to investigate the liquid bridge breakup with thermocapillary effect. The non-isothermal liquid bridge breakup in the viscous and inertial regimes are studied. It has been found that the inertial regime breakup exhibits different pinchoff shapes as the Capillary number increases, and that the viscous regime breakup is accelerated by the thermocapillary motion.

We present a novel dimensionally split Cartesian cut cell method to compute inviscid, viscous and turbulent flows around rigid geometries. On a cut cell mesh, the existence of arbitrarily small boundary cells severely restricts the stable time step for an explicit numerical scheme. We solve this `small cell problem' when computing solutions for hyperbolic conservation laws by combining wave speed and geometric information to develop a novel stabilised cut cell flux. The convergence and stability of the developed technique are proved for the one-dimensional linear advection equation, while its multi-dimensional numerical performance is investigated through the computation of solutions to a number of test problems for the linear advection and Euler equations. This work was recently published in the Journal of Computational Physics (Gokhale et al., 2018). Subsequently, we develop the method further to be able to compute solutions for the compressible Navier-Stokes equations. The method is globally second order accurate in the L1 norm, fully conservative, and allows the use of time steps determined by the regular grid spacing. We provide a full description of the three-dimensional implementation of the method and evaluate its numerical performance by computing solutions to a wide range of test problems ranging from the nearly incompressible to the highly compressible flow regimes. This work was recently published in the Journal of Computational Physics (Gokhale et al., 2018). It is the first presentation of a dimensionally split cut cell method for the compressible Navier-Stokes equations in the literature. Finally, we also present an extension of the cut cell method to solve high Reynolds number turbulent automotive flows using a wall-modelled Large Eddy Simulation (WMLES) approach. A full description is provided of the coupling between the (implicit) LES solution and an equilibrium wall function on the cut cell mesh. The combined methodology is used to compute results for the turbulent flow over a square cylinder, and for flow over the SAE Notchback and DrivAer reference automotive geometries. We intend to publish the promising results as part of a future publication, which would be the first assessment of a WMLES Cartesian cut cell approach for computing automotive flows to be presented in the literature.

O cenário atual da construção civil tem se caracterizado pelo uso crescente de novos produtos, materiais e tecnologias construtivas. Simultaneamente, a adoção de novas técnicas em detrimento a pouca abordagem científica e às falhas de projeto, execução e planejamento de obra têm colaborado para a ocorrência de manifestações patológicas. O desempenho do edifício resulta da contribuição individual de cada um dos materiais e elementos que o constituem, mas também depende do efeito gerado quando todo o conjunto é solicitado. Caso haja incompatibilidade entre as condições de deformação da estrutura de concreto, a capacidade de acomodar deformações da alvenaria e das camadas de argamassa pode desencadear-se desde pequenas fissuras no revestimento, rupturas na alvenaria até mesmo o colapso total da parede, gerando além de elevados custos e descrédito para as construtoras, principalmente, desconforto ao usuário. Atualmente existem diversas técnicas construtivas de reforço/reabilitação, de forma a distribuir tensões, compatibilizar deformações e garantir o desempenho à tração do revestimento de argamassa. Entre estas técnicas ressalta-se o uso de telas metálicas, que no Brasil é amparado por uma normalização ainda incipiente. Embora este uso seja recomendado, não há consenso quanto aos métodos executivos e parâmetros técnicos da tela metálica mais indicados para cada aplicação. Nesse contexto, o trabalho em questão, julgou importante contribuir para a avaliação do desempenho de revestimentos de argamassa com reforço de tela metálica e apresenta três propostas. Uma delas foi o ensaio de tração por compressão diametral, o qual se mostrou viável para avaliar a eficiência do uso de tela no incremento de resistência da argamassa, no entanto, permite ponderações restritas ao parâmetro de carga de ruptura. O ensaio de tração direta proposto para caracterizar o revestimento de argamassa reforçado com tela metálica, aplicado sobre a interface alvenariaestrutura, embora tenha execução complexa e demande mais tempo, apresentou variabilidade satisfatória e mostrou-se capaz para avaliar além da carga a resistência à tração. Por fim, o ensaio de tração na flexão em 4 pontos foi considerado apto para a caracterizar argamassas reforçadas com tela, diante da fácil aplicabilidade, com tamanho menor dos CP’s e variabilidade reduzida. Então foi usado para avaliar a influência de diferentes tipologias de telas metálicas e posicionamento delas na argamassa no desempenho à tração do revestimento. / The current scenario of the construction has been characterized by the increasing use of new products, materials and construction technologies. Simultaneously, the adoption of new techniques to the detriment a little and scientific approach to design failures, execution and construction management have contributed to the occurrence of pathological manifestations. The building performance results of the individual contribution of each one of the materials and elements constitute, but also depends on the effect generated when the whole set is requested. If there is incompatibility between the deformation conditions of the concrete structure, the ability to accommodate deformations of the masonry and layers of mortar, this may unleash from small cracks in the coating, breaks in the masonry even total collapse of the wall, generating high costs and discredit to the builders, mainly discomfort to the user. Nowadays there are many construction techniques reinforcement / rehabilitation, in order to distribute tensions, compatible deformations and guarantee performance to pull the mortar coating. Among these techniques emphasizes the use of metal mesh, which in Brazil is supported by an incipient normalization. Although this use is recommended, there is no consensus on the executive methods and technical parameters of the metal mesh best suited for each application. In this context, the work in question, considered it important to contribute to the evaluation of mortar coatings performance with metal mesh reinforcement and presents three proposals. One was the indirect tensile (Brazilian) test, which proved feasible to evaluate the use efficiency screen on mortar strength increase, however, allows considerations restricted to the breaking load parameter. The tensile direct test proposed to characterize the reinforced mortar coating metal screen applied to the masonry structure interface, although it has complex execution and demands more time presented satisfactory variability and shown to be able to evaluate the load and also the resistance to traction. Finally, the tensile test in bending at 4 points was considered suitable for the characterize mortars reinforced with screen, due to the easy applicability, have smaller size specimens and reduced variability. Then it was used to evaluate the influence of different types of metal mesh and positioning them in the mortar in performance to coating traction.

Internationally as well as in Sweden, efforts for improvement in gynaecological surgery in recent decades have mainly focused on three new treatment concepts: (1) Use of minimally invasive procedures: since there is an interdependency between the extent of surgical trauma and the risk for adverse outcome, increased use of supposedly atraumatic endoscopic procedures has revolutionized several aspects of surgical care (2) A multimodal approach to eliminate harmful procedures in the peri-operative process based on evidence-based principles (3) Introduction of implants to support damaged tissue with synthetic mesh in incontinence and pelvic organ prolapse patients. Research question 1: Is introduction of a minimally invasive operation enough per se or is the measured improvement mediated by elimination of harmful procedures in the perioperative process? Findings: Our study (Paper I) indicates that by applying a multimodal intervention programme for the pre- and postoperative care of patients undergoing supravaginal hysterectomy, the surgical procedure per se is of less importance than generally considered. Patient-related parameters such as length of postoperative hospital stay, number of days at home with need of painkillers, number of days before return to normal activities, and patient satisfaction did not differ between patients undergoing the laparoscopic procedure and patients undergoing abdominal supravaginal hysterectomy. When evaluating a new and presumably improved operative procedure against an established standard procedure, it is mandatory and of fundamental importance that the two methods are aligned in terms of perioperative care provided. Research question 2: Under which circumstances can it be assumed that a new surgical procedure showing promising efficacy in one setting can be reproduced with similar results in a different clinical setting (Paper I)? Findings: The operating surgeons concluded that, in their hands and under local conditions, laparoscopic technique for supravaginal hysterectomy was not superior to traditional open hysterectomy and stopped using laparoscopic technique. It seems necessary, prior to routine use, to monitor, using scientific tools, whether the advantages described in the literature are achievable under local conditions. Research question 3: Do expected advantages of implants outweigh the unwanted effects and complications caused by implants in operations for recurrent cystocele (Paper II)? Findings: Mesh has better durability but more (minor) complications. It is not possible to determine whether mesh is "generally better" than native tissue operation. Some may focus on the improved durability, others on the increased risks. The surgeon must make a risk assessment for each individual case. The patient must be sufficiently informed to understand the risks and make a personal, informed decision whether she wants an augmentation by implant. Essential for this process is a clear, comprehensible picture of both desired and unwanted effects of the planned surgery. In this context, studies like ours might be of use.

No description available.

In this thesis we develop 2D parallel unstructured mesh adaptation methods for the solution of partial differential equations (PDEs) by the finite element method (FEM). Additionally, we develop a novel block preconditioner for the iterative solution of the linear systems arising from the finite element discretisation of the Föppl-von Kàrmàn equations. Two of the problems arising in the numerical solution of PDEs by FEM are the memory constraints that limit the solution of large problems, and the inefficiency of solving the associated linear systems by direct or iterative solvers. We initially focus on mesh adaptation, which is a memory demanding task of the FEM. The size of the problem increases by adding more elements and nodes to the mesh during mesh refinement. In problems involving a large number of elements, the problem size is limited by the memory available on a single processor. In order to be able to work with large problems, we use a domain decomposition approach to distribute the problem over multiple processors. One of the main objectives of this thesis is the development of 2D parallel unstructured mesh adaptation methods for the solution of PDEs by the FEM in a variety of problems; including domains with curved boundaries, holes and internal boundaries. Our newly developed methods are implemented in the software library oomph-lib, an open-source object oriented multi-physics software library implementing the FEM. We validate and demonstrate their utility in a set of increasingly complex problems ranging from scalar PDEs to fully coupled multi-physics problems. Having implemented and validated the infrastructure which facilitates the finite-element-based discretisation of PDEs in a distributed environment, we shift our focus to the second problem concerning this thesis and one of the major challenges in the computational solution of PDEs: the solution of the large linear systems arising from their discretisation. For sufficiently large problems, the solution of their associated linear system by direct solvers becomes impossible or inefficient, typically because of memory and time constraints. We therefore focus on preconditioned Krylov subspace methods whose efficiency depends crucially on the provision of a good preconditioner. These preconditioners are invariably problem dependent. We illustrate their application and development in the solution of two elasticity problems which give rise to relatively large problems. First we consider the solution of a linear elasticity problem and compute the stress distribution near a crack tip where strong local mesh refinement is required. We then consider the deformation of thin plates which are described by the nonlinear Föppl-von Kàrmàn equations. A key contribution of this work is the development of a novel block preconditioner for the iterative solution of these equations, we present the development of the preconditioner and demonstrate its practical performance.