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Flexible buried structures
Houšť, Vladimír ; Hrdoušek,, Vladislav (referee) ; Barták,, Jiří (referee) ; Klusáček, Ladislav (referee) ; Stráský, Jiří (advisor)
The thesis is devoted to analysing of flexible buried arch structures. Modelling of the flexible concrete arch is carried out via a nonlinear finite element model that accounts for soil constitutive relations, soil-structure interactions, sequential construction stages and soil compaction. Advanced FE-model was verified by measurement obtained by full-scale field testing of two buried arches. Mathematical optimization methods of genetic algorithms and Levenberg-Marquardt method are applied to already calibrated complex computational models in order to reduce bending and associated flexural stresses in the concrete section of buried arch. Centre line of the arch is parameterized by cubic Bezier curve to reach interpolation of thrust line. Optimization technique is applied with extensive parametrical study which shows the optimal shapes for buried arches of various span/rise ratios, backfill depths and foundation soil types. For practical application are given coordinates of Bézier curve control polygons of particular resulting shape. Subsequently is applied optimization method for a theoretical reduction of tensile stresses obtained by shape optimization of previously verified numerical model of buried arch. Comparisons of earth pressure, bending moment axial force and deflection of flexible structure during sequential construction of different span/raise ratios of buried arches are presented. The behaviour of flexible buried arch with effect of local traffic load model LM1 has been analysed via 3D finite elements model with respect to different depth of backfill above crown.
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Shape optimization of the typical frame of the load-bearing structure of the steel hall
Kuzbová, Šárka ; Vlk, Zbyněk (referee) ; Hokeš, Filip (advisor)
The thesis deals with the shape optimization of a typical frame of a steel hall structure. The calculation is performed for two types of parametric models created with both 1D and 2D finite element models in RFEM 6. The aim of the optimization process is to achieve a state where the structure has the lowest mass while satisfying the stress limit. The first model, which is created using 1D finite elements, focuses on optimizing the initial and final section heights of the members with the raises. The following model, which is developed using 2D finite elements, is aimed at optimizing the openings of the pierced beam. The thesis also includes analytical verification of the model using the deformation method.
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Vortex rope mitigation of Francis turbine draft tube by shape optimization
Oberta, Brian ; Štefan, David (referee) ; Rudolf, Pavel (advisor)
This master's thesis is aimed at the creation of shape optimization algorithm. The subject of optimization is a Francis turbine's draft tube in a sup-optimal operational regime. The objective of the shape optimization is the mitigation of vortex rope. The shape optimization is based on steady two-dimensional CFD simulations with usage of k- turbulency modelling. The results are validated by more advanced unsteady three-dimensional CFD simulations. As a part of shape optimization, this thesis ivestigates the possibilities of a simulation of vortex rope's manifestations with steady two-dimensional CFD models.
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Shape optimization of civil engineering structure
Kuzbová, Šárka ; Vlk, Zbyněk (referee) ; Hokeš, Filip (advisor)
The bachelor thesis is focused on shape optimization of a selected load-bearing structure. The calculation is carried out in RFEM 6. The desired goal is to achieve an optimum state where the structure has the lowest mass and at the same time satisfies the ultimate and serviceability limit state. The optimization procedure of the selected structure is focused on optimizing the position of the diagonals. The bachelor thesis also includes a study of the shape optimization of the simplified statically certain and uncertain structure.
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Lubricant Gap Shape Optimization of the Hydrodynamic Thrust Bearing
Ochulo, Ikechi ; Vacula, Jiří (referee) ; Novotný, Pavel (advisor)
The objective of this Master's thesis is to find, using genetic algorithm (GA), an optimal profile for lubricating gap of a thrust bearing of a turbocharger. Compared to the analytical profile, the optimal profile is expected to have minimized friction for an equivalent load capacity. Friction minimization is one way to increase the efficiency of the thrust bearing; it reduces the friction losses in the bearing. An initial problem was given: a thrust bearing with Load capacity 1000 N, inner and outer radii of 30mm and 60mm respectively, rotor speed of 45000 rpm and angle of running surface of $0.5^0$. Lubricant properties were also provided for the initial problem: oil density of $ 840 kg/m^3$, dynamic viscosity $(\eta)$ of 0.01 Pa.s With this data, the numerical solution of the Reynolds equation was computed using MATLAB. To obtain more information, the minimum lubricating gap thickness was also computed using MATLAB. With this information, the shape of the analytical profile, and its characteristics were found. The analytical profile was then used a guide to create a general profile. The general profile thus obtained is then optimized using GA. The characteristics of the generated profile is then computed and compared to that of the analytical profile.
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Response surface method in connection with CFD for shape optimization
Pleva, František ; Štefan, David (referee) ; Rudolf, Pavel (advisor)
This thesis is focused on shape optimization of Venturi´s nozzle with optimization method called response surface method. The first part of this work is concerned with the description of this method as well as explaining the basic principle. Furthermore, there is an explanation of the application of this method in synchronicity with CFD and its operating algorithm. The second part of this thesis is then focused on simple example with plane wing and simplified optimization of Venturi´s nozzle in which this method was tested. In the third part there is described full multiparameter shape optimalization of the nozzle for two geometries.
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Lubricant Gap Shape Optimization of the Hydrodynamic Thrust Bearing
Ochulo, Ikechi ; Vacula, Jiří (referee) ; Novotný, Pavel (advisor)
Cílem této diplomové práce je najít optimální profil mezery mazání pro turbodmychadlo. Cílem je minimalizovat tření, udržovat nosnost a nezvyšovat průtok maziva. Tato multiobjektivní optimalizace se provádí pomocí genetického algoritmu (GA) v MATLABu. Minimalizace třecí síly snižuje ztráty třecího výkonu turbodmychadla. Řešení Reynoldsovy rovnice je počítáno numericky pomocí MATLABu. Je zjištěna minimální tloušťka mazací mezery pro počáteční problém. Funkce spline se používá ke generování obecného profilu mazací mezery. Tento profil je poté optimalizován pomocí GA v MATLABu.
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Modern trends in the design of frame machine
Holík, Štěpán ; Urbánek, Michal (referee) ; Zeizinger, Lukáš (advisor)
The bachelor's thesis deals with the issue of using modern methods of machine structures design, especially topological optimization. The first part describes the history of design, design methods in terms of approach to the technical problem and product development process. The second part discusses the various methods used in the design. The methods of topological optimization are compared and software solutions that enable topological optimization are described in detail. The fourth part deals with the dimensioning of components using topological optimization with a demonstration of important details on a specific example in Ansys Mechanical and MSC Apex Generative Design.
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