Le présent document a pour objet la modélisation transitoire non linéaire du comportement vibratoire des systèmes de frein aéronautiques. Le but est de reproduire numériquement l’apparition et le niveau des vibrations au cours du temps, afin de les maîtriser et d’adapter la conception du frein. Les essais de freinage mettent en évidence deux modes de vibration que sont le whirl et le squeal. Si les niveaux de ces vibrations deviennent trop importants, la structure de la roue et du train d’atterrissage peut être endommagée. Afin d’éviter de tels dommages, la conception du frein doit être adaptée. Pour réaliser cela, Messier-Bugatti-Dowty doit disposer d’un modèle capable de prédire les niveaux de vibration du frein au cours du temps pendant la phase de freinage. Le modèle doit avoir une précision suffisante, être en lien avec la maquette numérique et ne doit pas exiger de recalage. Un premier travail vise à améliorer le modèle éléments finis existant qui se révèle être trop imprécis. Une étude portant sur les effets gyroscopiques permet d’évaluer leur impact sur la fréquence et la stabilité des modes de whirl. Une modélisation plus complète du bâti d’essai améliore la précision de la fréquence du mode de squeal. Enfin, le mode de whirl est mieux simulé grâce au développement d’un modèle de pneumatique à partir de son analyse modale. Ce modèle est ensuite réduit afin de réaliser une intégration temporelle. Une sous-structuration permet de séparer l’ensemble des disques du frein, où le frottement et la non-linéarité se situent, du reste de la structure considérée comme linéaire. Trois techniques de réduction de l’ensemble des disques sont exposées. On évalue leur représentativité par rapport au modèle non-réduit en comparant les fréquences et la stabilité des modes propres. La première méthode est une représentation nodale de l’ensemble des disques. Les équations décrivant la non-linéarité et le frottement sont analytiques. Pour la deuxième méthode, la non-linéarité est déplacée à l’extrémité de l’ensemble des disques pour la découpler du frottement. La troisième méthode, plus ambitieuse et complexe, conserve à la fois l’emplacement de la nonlinéarité aux interfaces frottantes et la géométrie des disques. Une technique de réduction modale permet d’abaisser le nombre de degrés de liberté non linéaires. Pour clore ce rapport, des simulations transitoires sont calculées à partir des modèles réduits. Des études d’influences sont réalisées. Les paramètres étudiés sont le type d’algorithme d’intégration temporelle, l’amortissement introduit, la loi non linéaire, la pression hydraulique d’entrée et le coefficient de frottement. Leurs impacts sur les niveaux et la durée d’apparition des vibrations est évalué. / This report deals with the non-linear transient simulation of the dynamic behaviour of aeronautic brake systems. The objective is to reproduce the occurrence and level of vibrations versus time in order to control and adjust design consequently. The braking tests highlight two eigenmodes, which are called whirl and squeal. If the level of these vibrations becomes too high, the structures of the wheel and the landing gear may be damaged. To avoid damage, the design has to be adjusted. To achieve this, Messier-Bugatti-Dowty requires a model that is able to predict the levels of vibrations of the brake when it is braking. This model must have an adequate accuracy, be linked to the digital mockup and not require tuning. First, the existing finite element model has to be improved because its initial accuracy is not acceptable. A study about gyroscopic effects allows to assess their impact on the frequency and the stability of whirl modes. A complete modelling of the test frame improves the squeal modes’ frequency accuracy. At last, the whirl modes are better simulated due to the development of a tyre model based on modal analysis data. Then, the finite element model is reduced in order to perform a temporal integration. A substructuring allows to separate the set of brake discs (heat sink), where friction and non-linearities are located, from the rest of the structure which is considered linear. Three heat sink reduction techniques are proposed. Their representativeness are estimated compared to the non-reduced model. The first technique is a nodal description of the heat sink. The equations of friction and non-linearity are analytical. For the second technique, the non-linearity is displaced to the extremity of the heat sink to uncouple it from friction. The third technique, more ambitious and complex, keeps the location and non-linearity in friction interfaces and discs geometry. A reduction technique enables to decrease the number of non-linear degrees of freedom. As a conclusion, transient simulations are computed from reduced models. Sensitivity studies are performed. Studied parameters are the type of integration solver, introduced damping, non-linearities, hydraulic pressure, and friction coefficient. Their impacts on level and duration of occurrence of vibrations is estimated.

Parametry nahradniho obvodu synchronniho stroje znance ovlivnuji jeho chovani jak pri statickem provozu, tak predevsim pri nahlych dynamickych jevech a poruchovych stavech. Prace je zamerena na zhodnoceni dostupnych metod pro vypocet techto parametru pomoci Metody konecnych prvku. Prvni cast je venovana teoretickemu popisu zakladnich principu Metody Konecnych Prvku a jejich aplikaci na reseni problemu elektromagnetickeho pole v elektrickych strojich. Zaroven take shrnuje zakladni usporadani nahradniho obvodu synchroniho stroje, principi jeho konstrukce a zakladni funkci. Druha cast je venovana praktickemu vypoctu reaktanci nahradniho obvodu synchronniho stroje. S pomoci MKP jsou vypocteny synchronni reactance s uvazovanim vzajmeneho magnetickeho pusobeni proudu v d a q ose. Pro vypocet transientnich a subtransientnich reaktanci jsou navrzeny ctyri odlisne metody a jsou zhodnoceny z hlediska pozadovane presnosti vypoctu a narocnosti na vypocetni cas. Zaverecna cast popisuje zakladni merici metody pro urceni parametru nahrandniho obvodu na skutecnem stroji. Kapitola take obsahuje srovnani simulace trifazoveho zkratu synchronniho stroje s realnou zkouskou provedenou laboratorne. Zaver obsahuje srovnani jednotlivych metod a navrh optimalniho postupu pro vypocet zkoumanych parametru.

This diploma thesis deals with dynamic analysis of the steam turbine blade. This blade is part of the last row of low pressure level of steam turbine. Computational analysis has been performed in first part using FEM and software ANSYS. A Transient analysis has been used to solve forced vibrations. Main goal is to obtain a behavior of main stresses and its directions as a function of loading of the blade in the crack initiation area. Second part deals contain a an experiment. Experiment has been set up to perform a modal analysis which is necessary to obtain a fundamental numbers. Then the vibration of the blade has been performed. To perform this experiment same edge conditions as which has been used during the computational analysis. Goal is the same as in the first part – obtain a behavior of main stresses and its directions as a function of loading of the blade in the crack initiation area. The comparison of results obtained during experimental analysis and computational analysis has been performed in the last part of the thesis. Also the question if any geometrical nonlinearities appeared during analyses is answered.

This Master’s thesis deals with rotordynamics analysis of asynchronous generator rigid coupling with water turbine shaft. The purpose of this thesis was to determine influence of connection of generator with water turbine by rigid coupling to reactions in bearings. This problem was solved in two ways. The first option focused on model without influence of inaccuracies whereas there were inaccuracies included in the second option. The problem was solved by computational modeling by software Ansys.

The main goal of this thesis is dynamic analysis of shaft of booster pump QHD-200. In the beginning we offer basic equations generally used in dynamics and common/possible methods for their solution. Then we focus on specific problems connected with rotor dynamics and using simple Laval rotor we show their mathematical interpretation. Based on given load as accelerogram we create response spectrum in different ways (using different methods) and compare their CPU time demand. In the next part we make three finite element models of different physical level. We perform modal analysis and comparison of eigen frequencies, mode shapes. In following chapter transient analysis was performed on all models. As load we use accelerogram. We evaluate translations in particular positions of model. After that, we decide whether or not gap between impeller and stator case will be erased. Finally we make assessment of force acting upon bearings.

[pt] Testes de formação são normalmente realizados para determinar as propriedades rochosas do reservatório e os dados obtidos costumam ser interpretados com base no pressuposto que o reservatório é homogêneo na direção vertical e descrito por um modelo uni dimensional. No entanto, muitos reservatórios são compostos por diversas camadas que possuem características diferentes. Os poços de produção nesses reservatórios podem receber óleo de mais de uma camada. Em um sistema de reservatório estratificado, o comportamento da pressão e da temperatura não é necessariamente o mesmo de um sistema em camada única e raramente revela as mesmas propriedades médias de todo o sistema. Prever as características das camadas individuais é importante para descrever adequadamente o reservatório e melhorar o gerenciamento da produção. Este trabalho apresenta um modelo numérico, transiente-térmico para um sistema acoplado poço - reservatório 2D, levando-se em consideração efeitos Joule-Thompson responsáveis pelo aquecimento / resfriamento do fluido, expansão/compressão adiabática, além de efeitos de condução e convecção para o poço e o reservatório em um escoamento monofásico. A análise bidimensional do reservatório permite que se simule zonas de estratificação e barreiras. O modelo permite fluxo através de camadas adjascentes com propriedades de rocha diferentes. Pressão e temperatura a uma certa posição no poço produtor são avaliadas ao longo do tempo. Resultados mostram que a análise do transiente de pressão (PTA) e a análise do transiente de temperatura (TTA) podem ser utilizadas para caracterizar diferentes configurações de um reservatório estratificado. / [en] Well formation tests are usually performed to determine rock properties of a reservoir and the obtained data has often been interpreted based on an assumption that the reservoir is homogeneous in the vertical direction and described by a 1-D model. However, many reservoirs are found to be composed of different number of layers that have different characteristics. Production wells in such reservoirs may receive oil from more than one layer. In stratified reservoir system, the pressure and temperature behavior are not necessarily the same as in single layered system, and rarely reveals the same average properties of the entire system. The prediction of the characteristics of the individual layers is important to describe properly the reservoir and improve production management. This work presents a numerical transient-thermal model for a coupled wellbore/2D-reservoir considering Joule-Thompson heating/cooling, adiabatic fluid expansion/compression, conduction and convection effects for both wellbore and reservoir for a single-phase fluid flow. The two-dimensional reservoir model allows the analysis of stratified zones and barriers. The model allows cross flow between the adjacent layers with different rock properties.Wellbore temperature and pressure at a certain gauge depth are evaluated along the time. Results show how pressure transient analysis (PTA) and temperature transient analysis (TTA) can be used to characterize different configuration of stratified reservoirs.

For predicting the performance characteristics of highly utilized induction machines, commonly finite element analysis (FEA) is applied. If only the stationary behavior is of interest, both time-harmonic and transient calculations are feasible. Both procedures offer benefits and drawbacks regarding precision and computing time. In this paper the stationary torque-slip-characteristic of a squirrel cage induction machine for electric vehicle application is calculated by means of time-harmonic and transient FEA. The simulation results are compared to measurements taken on the test bench. For low saturation levels the time-harmonic and transient simulation produce nearly equivalent stationary torque results. For high saturation levels, the commonly used approach for nonlinear time-harmonic calculation is to use a corrected magnetization curve. It is shown that the assumption of sinusoidal time variation of the magnetic field strength usually made in this case results in a torque error increasing with the saturation level for the time-harmonic calculation.

Switches and crossings are vital components of the railway network. Obstacles to the smooth functioning of these components could result in delays and network traffic. Given the geographical location of Sweden, snow is one of the major obstacles for the switches. The presence and hardening of snow act as an obstacle to the movement of the switch rail, thus hindering its function. Electrically heated switches melt and clear the snow for movement of the switch rail. They typically operate at a power level of 10 kW–30 kW. With 6800 switches operational in Sweden, the potential for energy savings is huge. This master thesis intends to investigate the possibility of reducing energy consumption through insulating a side of the rail. To achieve that, a comprehensive transient conjugate heat transfer analysis is carried out using CFD simulations. The initial refinement of the measured data highlighted the uncertainties in them, and which shaped the course of the thesis. The analysis of these uncertainties gave critical insights and led to useful recommendations for future work. The fluid-solid interactions between the rail and flow of air and their impact on transient heat loss have been analyzed to gain critical insights regarding the choice of side of implementation of insulation. The validation of the model at lower electrical power levels threw light on the dire requirement of numerical modeling of snow melting, which happens at the higher power levels of the heating element. One of the critical observations made after the implementation of the insulation is the reduction in the temperature of the heating element, which leads us to conclude that the insulation not only saves energy but also prolongs the life of the heating element by reducing thermal fatigue. / Växlar och korsningar är viktiga komponenter i järnvägsnätet. Om dessa komponenter inte fungerar smidigt kan det resultera i förseningar och avbruten nätverkstrafik. Med tanke på Sveriges geografiska läge är snö ett av de största hindren för växlarna. Snö och hårt packad snö kan hindra spårväxelns rörelse och funktion. Elektriskt uppvärmda spårväxlar smälter bort snön så att spårväxeln kan fungera. Spårväxlarna har vanligtvis en effektnivå på 10 kW - 30 kW. Med 6 800 växlar i drift i Sverige är potentialen för energibesparingar är enorm. Denna masteruppsats syftar till att undersöka möjligheten att minska energiförbrukningen genom att isolera en sida av rälsen. För att uppnå detta utförs en omfattande transient konjugerad värmeöverföringsanalys med hjälp av CFD-simuleringar. Den inledande dataförädlingen av mätdata belyste osäkerheterna i datan vilket formade det fortsatta arbetet med avhandlingen. Analysen av dessa osäkerheter gav kritiska insikter och användbara rekommendationer för framtida arbete. Fluid - solid-interaktionerna mellan skenan och luftflödet och deras inverkan på den transienta värmeförlusten har analyserats för att få kritiska insikter om valet av sida för isolering. Valideringen av modellen vid lägre effektnivåer kastade ljus över det akuta behovet av numerisk modellering av snösmältningen som sker vid värmeelementets högre effektnivåer. En av de kritiska observationerna som gjordes efter implementeringen av isoleringen är minskningen av värmeelementets temperatur, vilket drar slutsatsen att isoleringen inte bara sparar energiförbrukningen utan också förlänger elementets livslängd genom att minska den termiska utmattningen.

No description available.

[pt] O rebaixamento e controle das águas subterrâneas são atividades implementadas e monitoradas de forma contínua ao longo da vida dos projetos de mineração subterrânea ou a céu aberto. A implementação apropriada e eficiente destas atividades depende de estudos hidrogeológicos de grande porte, que permitem avaliar os sistemas de controle mais adequados. A procura da eficiência técnico-econômica destes processos demanda análises numéricas de fluxo tridimensionais de toda a região em estudo, caracterizada por profundas e complexas estratificações de materiais permeáveis abaixo do lençol freático, como normalmente abrangem projetos de mineração, onde as soluções analíticas não podem mais ser aplicadas. O presente trabalho de pesquisa contribui na melhor compreensão das formulações numéricas que representam o comportamento do fluxo subterrâneo, através de dois estudos de caso, o primeiro em uma mina subterrânea e segundo em uma mina superficial. No caso da mina subterrânea foram incorporadas feições cársticas através de elementos discretos 1D dentro de um modelo tridimensional de elementos finitos com o intuito de representar caminhos preferenciais de fluxo. Foram discutidas as vantagens de incorporar tais feições de forma explicita, quantificando o fluxo que passam por estas, que alimentam à mina através de conexões diretas com um rio adjacente. Estes elementos discretos permitem uma representação mais realista do meio hidrogeológico e ao mesmo tempo, uma avaliação mais aprimorada dos efeitos no comportamento do fluxo subterrâneo devido à impermeabilização superficial do rio, como a solução mais coerente para este problema de infiltração. Também foi elaborado um modelo hidrogeológico conceitual para representar o comportamento hidrogeológico de uma mina a céu aberto, desenvolvendo uma sistemática de uso adequado das condições de contorno e de restrição, a calibração deste modelo e a verificação de diferentes cenários de fluxo, como resultado da incorporação das diferentes técnicas de controle das águas avaliadas em regime transiente, que abrange poços de bombeamento, paredes cut-off assim como ponteiras filtrantes e drenos horizontais. As diferentes técnicas modeladas mostraram resultados satisfatórios, sendo que arranjos de várias técnicas, configuradas de forma localizada, resultam ser mais recomendáveis e eficientes para tratar problemas particulares. / [en] Dewatering and groundwater control are activities continuously implemented and monitored throughout the duration of underground mining or open pit projects. The proper and efficient implementation of these activities depends on large hydrogeological studies, for assessing the most appropriate control systems. The demand for technical and economic efficiency of these processes requires three-dimensional flow numerical analysis of the entire study area, characterized by deep and complex stratifications of permeable materials below the water table, as usually cover mining projects, where analytical solutions cannot be applied. The present research contributes to a better understanding of the numerical formulations that represent the behavior of groundwater flow via two case studies—the first in an underground mine and the second in a surface mine. In the case of the underground mine, 1D discrete elements were incorporated within a finite-three dimensional model in order to represent preferential flow paths. The advantages of incorporating such features explicitly to quantify the flow passing through them, that feed the mine through direct connections with an adjacent river, were discussed. The use of discrete elements allows for a more realistic representation of the hydrogeological environment and, at the same time, a more refined assessment of the effects on the behavior of groundwater flow due to surface sealing of the river, as the most coherent solution to this infiltration problem. Furthermore, a conceptual hidrogeologic model representing the hydrogeological behavior of an open pit mine was created, developing a system of the appropriate use of boundary and constraint conditions, calibrating the model and verifying different flow scenarios, as a result of the incorporation of different water control techniques assessed in transient regime, such as covering pumping wells, cut-off walls as well as wellpoints and horizontal drains. The different techniques modeled showed satisfactory results, with various arrangements of techniques configured in a localized form resulting in the most desirable and efficient treatments for particular problems.