Beschreibung der Finite Elemente Software-Familie SPC-PM3-AdH-XX für: (S)cientific (P)arallel (C)omputing - (P)rogramm-(M)odul (3)D (ad)aptiv (H)exaederelemente. Für XX stehen die einzelnen Spezialvarianten, die in Teil 2 detailliert geschildert werden. Stand: Ende 2013

We study the flow of a dilute polymer solution in a wavy channel under steady-state flow conditions by employing the non-equilibrium thermodynamics two-fluid model (Mavrantzas-Beris, 1992), allowing for the coupling between polymer concentration and polymer stresses. The resulting highly complex system of partial differential equations describing inhomogeneous transport phenomena in the fluid are solved with an efficient implementation of the mixed finite-element method. We present numerical results for polymer concentration, stress, velocity and fluxes of polymer as a function of the non-dimensional parameters of the problem (the Deborah number , the Peclet number , the Reynolds number , the ratio of the solvent viscosity to the total fluid viscosity , and the constriction ratio of the channel width ). We find that the constricted part of the wall is depleted of polymer, when the polymer diffusion length-scale, expressed by the ratio of / , increases. The migration is more pronounced for macromolecules characterized by longer relaxation times, and takes place towards the expanding part of the channel or towards the centerplane. Migration is also enhanced by the width variability of the channel: the more corrugated the channel, the stronger the transfer of polymer to the centerplane. This increases the spatial extent of polymer depletion near the wall or induces a zone of sharp variation in polymer stress and concentration, which moves away from the channel wall, especially in lower polymer concentration. The development of a polymer-depleted layer smooths out the boundary layer which is known to arise with Boger fluids at the walls of such corrugated channels or tubes and gives rise to an “apparent” slip in the constricted section of the wall and to a very low value of the drag force on the wall. When and where boundary layers arise, they scale as (1/De) for the stresses and as (De⁄Pe)^(1⁄3) for the concentration. / --

In the present study, a computational method was developed, validated and applied for the determination of parameters of a constitutive model for a ceramic material. An optimization algorithm, based on a direct search method, was applied to the determination of the load-displacement response of the specimen, and for the identification of the parameters of the constitutive model.A one-dimensional nonlinear initial-boundary value problem of wave propagation in a composite bar made of dissimilar materials was formulated and solved numerically. Convergence of the numerical scheme was studied, and range of convergence was established. Numerical scheme was validated for a number of benchmark problems with known analytical solutions, and for the problems solved using finite element method. Investigation of the accuracy of the displacement and strain responses was conducted; known limitations of the Kolsky's method for split Hopkinson pressure bar were revealed. For numerical examples considered in the present study, comparison of performance of the optimized finite-difference solver and of the finite element code LS-DYNA showed that the finite-difference code is about 10 times faster.Developed method and solutions were applied for the identification of the parameters of the Johnson-Holmquist constitutive model for five sets of experimental data for aluminum oxide AD995. Results of analysis revealed significant sensitivity of stress response to variation of fractured strength model parameters and damage model parameters.For the determined values of parameters, detailed parametric study of stress field, damage accumulation, and velocity field, was conducted with the help of the finite element method.It was found that the accuracy of the simulation using the JH-2 constitutive model changes with the rate of damage accumulation in the ceramic material.The damage patterns and history of damage development, obtained numerically, agreed qualitatively with the fracture history and its patterns, observed in the recovered Macor ceramics available in the literature.A method for image analysis of the photographic images of the lateral sides of the recovered specimen was proposed. It was used to quantify density of the damage in the specimen and to establish a better integral approach to predict amount of damage inside the specimen.

In order to achieve results that are reliable when using the finite element method one has to use an acceptable element mesh with respect to the shape and size of the elements. As a help to produce an acceptable mesh there are quality criteria that must be fulfilled in most pre-processors. One objective with this thesis is to perform a sensitivity study that can be used as a basis for a Mesh guideline for chassis parts which is requested from engineers at Volvo 3P. The software used in the sensitivity study is ANSA as pre-processor, Nastran as solver and Metapost as post-processor. In the first part of the sensitivity study three different models are used for studying quality criteria such as aspect ratio, skewness, mid point alignment, mid point deviation and element size. Solid elements of second order, which are used in the three models, can be generated in two ways, which constitutes another part of the sensitivity study. They may either be generated from the beginning or can be converted from first order elements. This means geometrically that if second order elements where generated from the beginning the element mesh would follow the shape of the component in a better way compared to the other method. Recently a pre- and post-processing program called SimLab was introduced on the market. Since SimLab supports geometry import from several CAD-systems without loss of feature information, the automatic element mesh generation is supposed to be better as the mesh generator has access to more information concerning the geometry. An evaluation of SimLab is the second major objective of the thesis. More specifically, the evaluation concerns the possibility of using the software at Volvo 3P. Results show a surprising insensitivity regarding the criteria and that the method of generating second order elements from the beginning is to be preferred. SimLab is a new program with big potential and the conclusion is that it is possible to use it at Volvo 3P.

Radio frequency ablation (RFA) is a commonly used minimally invasive method of treating liver cancer tumours which utilises RF current for heating tumour tissue up to a lethal temperature. RF current is generated by a power generator and applied to the tumour by an electrode which is inserted into the tumour either during percutaneous or open surgery. RFA is a method that has great advantages compared to traditional surgical resection of tumours due to minimal invasiveness, it can be used for a greater number of patients and enables repeated treatments. Even though there are many advantages coupled to RFA there are still some problems and difficulties associated with the method. One of these problems is the cooling effect from large vessel blood flow within the liver, the so called heat sink effect. The aim of this master thesis work has been to develop a theoretical finite element model of RFA within Comsol Multiphysics software. This theoretical model has been used to simulate blood perfusion effects on resulting ablation volume. The effects from different large vessel blood flow parameters has been investigated, these parameters are: blood flow velocity, blood vessel diameter and distance between blood vessel and RF electrode. A factorial design has been utilised to setup parameter levels for the different simulations. A linear- and a second degree regression model has been calculated based on simulation results. The parameter with largest impact on simulative ablation volume and the interaction effects between the parameters were determined from the regression model coefficients. In addition to this has two simulations been performed, modelling perfused- and unperfused liver tissue, in order to investigate the effects resulting from microvascular perfusion. The result shows that the parameter with largest impact on simulative ablation volume are the distance, it was also shown that there are a small interactional effects between diameter and distance, where a small distance increases the effect from a varying diameter. Modelled microvascular perfusion was shown to give a decrease in simulative ablation volume. A shortage of this master thesis work is the lack of experimental verification of the developed model.

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Les Méthodes par Eléments Discrets apparaissent comme les méthodes les plus appropriées pour modéliser le caractère divisé. De nombreux travaux ont permis de mieux comprendre leurs comportements, mais dans certain cas se pose la question de l'impact du choix de la description volumique ou des lois d'interaction sur le comportement global du milieu. Dans ce contexte, en se basant sur l'approche "Non Smooth Contact Dynamic" permettant naturellement de mixer les différentes formulations, nous nous proposons de comprendre et d'analyser l'influence de cette description. Pour cela, nous utilisons deux applications différentes liées aux comportement quasi-statique (QS) des milieux granulaires et comportement dynamique des interfaces tribologiques. Au niveau de l'étude QS est faite en utilisant des essais de compression biaxiale et de cisaillement. Contrairement aux approches classiques, des particules déformables sont utilisées ici. Les résultats obtenus sont comparés en utilisant des outils de mesure tels que la relation contrainte-déformation, la compacité... Les résultats montrent qu'il n'est pas possible à partir d'une description rigide de converger vers des modèles déformables et souligne l'importance d'effectuer une analyse complète en tenant compte de la déformation des particules. Au niveau de la modélisation d'une interface tribologique s'intéresse à l'influence des conditions limites, des descriptions des premiers corps et du troisième corps sur la rhéologie de l'interface. Dans chaque simulation, frottement macroscopique, profils de vitesse et de contrainte sont observés. Les différents modèles utilisés ont peu d'influence sur la valeur du frottement mais plus d'influence sur les profils de vitesse au travers de l'épaisseur de troisième corps. Ceci souligne l'importante du choix du modèle lors de l'étude de la rhéologie de l'interface et montre qu'il est difficile d'obtenir des résultats génériques et ceci aussi bien en modèles bi que tridimensionnel.

Research area and topicality of the work. Mechanical properties and their evolution under loading are the most significant factors for the development of various mechanical structures, technologies and equipment. It seems to be natu-ral that deeper understanding of the behaviour of existing and design of new materials presents a challenge in different research areas. It should be noted, that all the materials are heterogeneous in meso- and micro- scales. They exhibit essential differences, compared to the macroscopic continuum behaviour. Basically, both experimental and numerical simulation methods are extensively applied for investigation purposes. Experimental techniques, capable of giving a realistic view of the inside of the material and extracting the real data, are very expensive. Therefore, the nu-merical simulation tools are extensively used as an alternative for investigation purposes. They have considerable advantages allowing the reproduction of multiple experiments and providing comprehensive data about ongoing phe-nomena. Recently, numerical technologies have become highly multidisciplinary subjects. They comprise phenomenological and statistical ideas, while mathe-matical models employ the relations of continuum mechanics, classical discre-tization methods and molecular dynamics. The Discrete Element Method (DEM) is one of new methods. It is aimed at simulating the dynamic behaviour of the contacting particles. Variable topology of the system of particles is an... [to full text] / Tyrimų sritis ir darbo aktualumas. Kuriant modernias ��vairios paskirties mechanines sistemas, technologijas ir įrangą, svarbiomis tampa jas sudarančios medžiagos. Savaime suprantama, kad žinomos ir naujai kuriamos medžiagos dabar kur kas išsamiau nagrinėjamos daugelyje mokslo šakų, įskaitant ir me-džiagų mechaniką. Visos medžiagos mezo- ir mikrostruktūros požiūriu yra ne-vienalytės. Jų mikroskopinės savybės skirtingos, lyginant su įprastu kontinuu-mu. Medžiagų savybėms tirti dažniausiai taikomi eksperimentiniai metodai. Eksperimentiniais metodais ištirti medžiagos struktūras ir jose vykstančius procesus ir įvertinti tam tikras jų savybes labai brangu. Tai viena priežasčių, kodėl skaitinis modeliavimas tampa realia tyrimų alternatyva. Skaitinį eksperi-mentą galima kartoti daug kartų, valdant bandinio parametrus, išlaikant tas pa-čias sąlygas, ir stebėti reiškiniui būdingus rodiklius visame tūryje. Šiuolaikiniai modeliavimo metodai yra kompleksiniai. Jie jungia fenome-nologines ir statistines idėjas, o matematiniai modeliai sudaromi taikant konti-nuumo mechanikos ir jų diskrečiųjų modelių bei molekulinės dinamikos pri-klausomybes. Diskrečiųjų elementų metodas (DEM) taip pat priskiriamas šiuo-laikinių metodų kategorijai. Jis skirtas kontaktuojančių dalelių sistemų dinami-niam modeliavimui. Kintanti dalelių sistemos topologija – būdingas metodo požymis. Pastaruoju metu DEM jau taikomas kontinuumui modeliuoti ir praktikoje aktualiems irimo uždaviniams spręsti. Reikia pastebėti... [toliau žr. visą tekstą]

The numerical analysis of electromagnetic railgun dynamics under transient load is considered in current PhD thesis. The object of investigation is electro-magnetic accelerator EMA-3 at French-German institute of Sain-Louis (ISL). The aim of work covers the development of the finite element model of the EMA-3 rail gun and its application for investigation of the mechanical behaviour of railgun under differently induced loading regimes. There are several tasks under consideration. The first one is development of the finite element model. The 2D model consisting of four node plane and elastic springs was suggested and examined. The second one is evaluation of influence particular loading to dynamic behaviour and giving of recommendations. This thesis contains introduction, four chapters, the summary of results and conclusions, and the list of cited literature and list of publications of the author. In introductory chapter, the problem is formulated and relevance of the work is discussed. The goals and objectives of the work, research methodology and scientific novelty, practical significance and defended propositions are briefly described. Publications and reports at conferences on the theme of dissertation are presented at the end of introduction. The first chapter covers the review of the references on the electromagnetic railgun. It contains description of the development history, physical principles and decisive factors. Later, the gun structure is considered with the... [to full text] / Disertacijoje baigtinių elementų metodu nagrinėjamas elektromagnetinės šaudyklės (EMŠ) konstrukcinių dalių mechaninis būvis, veikiant dinaminei ap-krovai. Tyrimo objektas yra EMŠ „EMA-3“. Šaudyklės mechaninė dalis sudaryta iš elektrai laidžių bėgių, pritvirtintų prie dielektrinio pagrindo. Tiriama mechani-nio būvio rodiklių priklausomybė nuo apkrovos pobūdžio ir šaudyklės bėgių įtvirtinimo. Šaudyklės mechaninio būvio nustatymas jos darbo metu leistų tiks-liau prognozuoti jos elgseną, pagreitintų projektavimą, tobulinimą ir atpigintų eksploatavimą. Disertacijos tikslas yra skaitiniais metodais aprašyti ir ištirti šau-dyklės mechaninį deformavimą, veikiant dinaminei apkrovai, ištirti mechaninio būvio rodiklių priklausomybes nuo apkrovos parametrų, palyginti skirtingus ap-krovų režimus. Remiantis gautais skaičiavimo rezultatais, siekiama įvertinti šių veiksnių įtaką ir teikti siūlymus režimų patobulinimui. Darbe spręsti keli uždaviniai: sudarytas ir ištirtas „EMA-3“ šaudyklės skaiti-nis baigtinių elementų modelis. Pasiūlytais rodikliais įvertintas šaudyklės mecha-ninis būvis ir palyginta realių apkrovų įtaką bėgių deformavimui. Uždaviniai su-formuluoti atsižvelgiant į esamų modelių ribotumą, į šaudyklės rezonansinę elgseną kritinio greičio aplinkoje ir į tinkamo darbinio režimo parinkimo proble-mą. Disertaciją sudaro įvadas ir keturi skyriai. Įvade apibrėžta tyrimų sritis ir aktualumas, aprašyta mokslo problema, su-formuluotas darbo tikslas ir uždaviniai, paminėti naudoti tyrimo... [toliau žr. visą tekstą]

Magistriniu darbu, kurio tema “Vertikalios ašies vėjo jėginės sparno modeliavimas“, siekiama ištirti mažos galios, paprastos konstrukcijos, vertikalios ašies vėjo jėgainės sparnuotes, atlikti jų kompiuterinį modeliavimą ir analizę. Tema yra aktuali dėl to, kad norint būti energetiškai nepriklausomiems, reikia ieškoti alternatyvių energijos šaltinių, kurie būtų neišsenkantys, prieinami daugeliui vartotojų. Vienas iš tokių - vėjo srauto energija, tačiau gyvenant tankiai užstatytoje, geografiškai šiurkščioje aplinkoje, tenka ieškoti mažų matmenų, mažos galios įrenginių, kurie pajėgtų dirbti esant mažiems vėjo greičiams ir sūkurinėmis sąlygomis, nedarkytų gamtos ar pastatų estetinės išvaizdos, nekeltų triukšmo ir būtų kuo lengviau aptarnaujami. Atliekant tyrimą, VAVJ sparno modelio analizės skaičiavimai buvo daromi remiantis bendrąja hidrodinaminių srautų teorija, naudojant baigtinių elementų analizės, projektavimo ir modeliavimo programą - COMSOL Multiphysics. Atlikti tyrimai parodė, kad didesnį sukimo momentą gausime naudodami uždarų galų rotorius, o įrengus oro srautą kreipiančias mentes, slėgis į rotoriaus sparną ženkliai išauga. Statant šachmatine tvarka keletą VAVJ, didžiausią slėgį į sparnuotes gausime esant 6 kartus didesniam atstumui nei sparnuočių spindulys. / The aim of this master's dissertation on the theme of "FEM modeling of vertical wind turbine using CFD solvers" is to investigate the low-power, simple design, vertical axis wind turbine impellers and to carry out their computer simulation and analysis. The theme is of great importance so as to be energectically independent, it is also necessary to look for alternative energy sources that are inexhaustible and accessible to many users. One of them - the wind flow energy, but living in a densely built-up, geographically rough environment forces us to look for small footprints, low-power devices that would be able to work at low wind speeds and eddy terms wouldn't damage natural and aesthetic appearance of the buildings making no noise and also maximize opportunities to be serviced. The study of VAWT wing pattern analysis calculations were made based on the general theory of hydrodynamic flows, using finite element analysis, as well as design and simulation software - COMSOL Multiphysics. Research has shown that we will get bigger torque while using closed ends of the rotors, and the installation of air flow directing vanes, the pressure in the rotor wing significantly increases. Constructing in a checkered order a few VAWT, the greatest pressure on the impellers receives 6 times greater distance than the impeller radius.