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Solution methods for an aeroelastic problem with combined harmonic and stochastic excitation
Fischer, Cyril ; Náprstek, Jiří
Assessing responses in slender engineering structures facing both deterministic harmonic and stochastic excitation is often based on an approximation by the single-degree-of-freedom van der Pol-type nonlinear model. Determining the response probability density function involves solving the Fokker-Planck equation, which is generally a challenging task. Hence, semi-analytical and numerical methods come into play. This contribution reviews several possible techniques and spotlights the exponential-polynomial-closure method. The shown results are limited, as the paper reflects an early stage of the relevant research direction.
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Computational modeling of radial hydrodynamic bearings for water machines
Pokorný, Jan ; Šimek,, Jiří (referee) ; Návrat, Tomáš (advisor)
The aim of this thesis is to calculate the stiffness and damping coefficients for radial hydrodynamic bearings. Cylindrical and lemon hydrodynamic bearings are considered. The solution to this problem mainly depends on the hydrodynamic pressure in the bearing. The numerical solution of the Reynolds equation is used to calculate the pressure. The effect of variable viscosity and density of the lubricant due to temperature changes is considered. The static equilibrium position of the journal centre is also solved. The stiffness and damping coefficients are determined using small amplitude journal motions about the equilibrium position. Three methods for determining these coefficients are presented. The outcome of this thesis is an algorithm for the calculation of stiffness and damping coefficients for cylindrical and lemon bearings. Results for lemon bearings are presented and comparison with the commercial software DynRot BR is made. The benefit of this thesis is the creation of an algorithm for the calculation of journal centre equilibrium position, a new way of incorporating the temperature changes in the viscosity and the density of the lubricant, and the modification of a method for calculating stiffness and damping coefficients based on experimental analogy.
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Stress-strain analysis of stadium lighting mast
Tokoš, Richard ; Kovář, Jaroslav (referee) ; Fuis, Vladimír (advisor)
The bachelor thesis contains an analysis of a steel structure that serves as lighting in a football stadium. The main goal is to create a bar system, the equation of static equilibrium and the deformation condition and I will analytically solve the stress and strain. Then I will create a model in ANSYS and calculate the stress and strain numerically. The bachelor thesis contains a comparison of the results of these methods.
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Assisted Code Vectorization and Parallelization Using the OpenMP 4.0 Standard
Slouka, Lukáš ; Nikl, Vojtěch (referee) ; Jaroš, Jiří (advisor)
The subject of the bachelor's thesis is code optimization using the OpenMP 4.0 standard which provides tools for assisted parallelization and vectorization. In addition to the descrip tion of the OpenMP 4.0 standard, the thesis as well contains an insight into architectures of modern computers, specifically the system of cache memories and SSE/AVX modules that play a major role in the optimization field. The thesis demonstrates advantages of optimized code compared to unoptimized version on a set of benchmarks which are aimed at various aspects of optimization.
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Significance of tensile stresses in a bended beam with constrained axial deformation
Wolf, Jonatan ; Profant, Tomáš (referee) ; Burša, Jiří (advisor)
Bachelor’s thesis deals with the significance of tension stresses produced by the bending of a beam with avoided longitudinal deformation. This problem is mainly solved by exact calculations of tensile stresses for different kinds of geometry, materials and the size lateral loads of the beam. The solution is done numerically using the MATLAB program. The result of this work is the assessment of tensile stress significance and comparison with other stresses, namely temperature stress. One of the partial results of the work is also the determination of the limit value of the slenderness of the beam for the given bending stress for which this tensile stress becomes significant.
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Modelling and simulation in aviation
Prešinský, Ján ; Nechvátal, Luděk (referee) ; Zatočilová, Jitka (advisor)
This bachelor thesis is focused on specifying the orientation of aircraft in normal Earth- xed frame. It is devoted to Euler angles representation and quaternions representation. Moreover, it introduces the equations of motion with 3 and 6 degrees of freedom and proposes the numerical method for solving these equations, which are expressed by the set of non-linear diferential equations.
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Analysis of possibilities of solution of buckling of a screw-shaped beam
Pokorný, Jan ; Fuis, Vladimír (referee) ; Burša, Jiří (advisor)
Bachelor’s thesis deals with the effect of the pretwist of a column on the increase in buckling load and also focuses on a column with rectangular cross section. This problem is divided into two main parts. The first one is represented by the column with a large thread pitch, the second one by a small thread pitch. The results are obtained by a numerical approach using MATLAB software. The verification is carried out via finite element software. The outcome of this thesis is plotting the ratio of the critical loads of the twisted and prismatic columns against the ratio of the side lengths of the rectangular cross section. The results are shown for both types of considered columns.
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Stress-strain analysis of the Gbely drilling tower
Vizváry, Peter ; Kovář, Jaroslav (referee) ; Fuis, Vladimír (advisor)
The content of the bachelor's thesis is focused on the stress-strain analysis of a drilling tower located in Gbely. Its main goal is to compile equations of static equilibrium for the analytical solution of the structure and its subsequent numerical verification using the created 3D computational model based on various static loads or changes in the degree of static determinacy. The first part of this work summarizes the theory of the bar and of bar systems, the basic limit states and the finite element method (FEM). The second part contains a search on the history of oil production in Slovakia, its discoverer and the development of deep drilling and production technologies. The third part describes the drilling tower in Gbely. The content of the fourth part is the creation of a 3D computational model of a real structure, which should represent the drilling tower as accurately as possible. The most comprehensive is the fifth part, which consists of the design of a simplified structure, writing the equations of static equilibrium for the analytical solution, creating a 3D computational model for numerical verification of the analytical solution and evaluating the conclusions to which the individual variants of the solution led.
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Analysis of performance of embankment constructed on subsoil improved by vertical drains
Kováč, Vladimír ; Miča, Lumír (referee) ; Chalmovský, Juraj (advisor)
The thesis deals with the back analysis of the instrumentated embankment on the subsoil, improved by prefabricated vertical drains. The first part is devoted to the theory of consolidation calculation. Furthermore, the author deals with a parametric study of the analytical calculation of prefabricated drains and the comparsion of the analytical and numerical solution. The last and the largest part of the work is a back analysis of the embankment which was built as a part of the subsoil improvement near the Suez Canal in Egypt by Keller GmbH.
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