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Modal Analysis of the Swirl Turbine Rotor Blades
Pekar, Marek ; Chromek, Lukáš (referee) ; Lošák, Petr (advisor)
The aim of this diploma thesis is to determine and compare modal properties of four swirl turbine wheels, each with a different geometry. Natural frequencies and mode shapes were obtained based on computer modelling using Ansys software and they were compared with experimental modal analysis' results. The computer modelling and the experimental modal analysis were carried out for different boundary conditions and in different environments. The beginning of the thesis is dedicated to a brief overview of literature with similar issues. Then a brief introduction of a dynamics theory is mentioned in which equations of motion for a damped and an undamped single degree of freedom system are derived. The creation of a geometry model which is obtained by a reverse engineering is shown in the second part of the thesis. The geometry model was subsequently used for the computer based modelling of the modal parameters. In the third part an experimental equipment, setting, measurement and processing of data are described. The conclusion of the thesis is dedicated to the comparison of the results obtained by the experimental modal analysis and the computing modelling is presented. Moreover, influence of boundary conditions and influence of the environment on the natural frequencies are evaluated.
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Dynamic behavior od rotor dynamics stystem vibrating in a liquid
Chlud, Michal ; Pochylý, František (referee) ; Malenovský, Eduard (advisor)
This thesis deals with dynamic behavior of swirl turbine vibrating in a liquid. Primarily is studied decrease of natural frequencies of rotor due the interaction with fluid environment, namely for different levels of submerged rotor in fluid. After that follows the detection of natural frequencies of swirl turbine in operating speed. The problem is solved by computational modeling in ANSYS system. For this solution is used acoustic elements method. The results are compared with experiment.
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Dancing liquid - vibration eigenmode shapes of liquids
Urban, Ondřej ; Pochylý, František (referee) ; Rudolf, Pavel (advisor)
This bachelor's thesis deals with phenomena connected with vertically oscillating liquid layer, particularly with Faraday waves and liquid atomization. More in detail it deals with the linear mathematical model for vertically oscilating inviscid and incompresible liquids by Benjamin & Ursell (1954). It also presents the appearance of these and other phenomena connected with liquid vibration in practical applications. Furthermore, results of experiments are presented. Their aim was to find some eigenmode shapes using the linear model and also to document some of their properties. Final part is aimed to the design of an experimental device for visualization of vibration eigenmode shapes of liquids.
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Evaluation of aerodynamic damping and natural frequencies from numerical simulations and experiments
Chládek, Štěpán ; Horáček, Jaromír ; Zolotarev, Igor
The paper describes different ways for aerodynamic damping and natural frequencies evaluation in a problem of fluid-structure interaction. It is useful for both numerical simulations and experimental measurements. The Fourier transform is used for the frequency evaluation and the damping is evaluated both in time and frequency domain. Significant influence of the chosen sampling frequency and the length of time record on the accuracy of the results are demonstrated both in the numerical simulation and in the experiment that was performed with the flexibly supported profile NACA 0012 with two degrees of freedom.
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Numerical Simulation and Experimental Modelling of Fluid - Structure Interaction in Veins
Štembera, V. ; Chlup, Hynek ; Maršík, František
The mixed formulation of the finite element method with the separately interpolated pressure is used for the numerical simulation of the fluid structure interaction. To describe a wider class of problems we consider in the simulation the three material models: the Neo-Hookean, the isotropic Gent model and the anisotropic Gent material model to include the influence of collagen structure of blood vessels. The fluid is modelled as Newtonian liquid. The strong coupling of both structure and fluid solvers allow us to simulate large deflection oscillations of the structure. The special experimental mock up line was designed for the investigation of unsteady fluid structure phenomena. Latex tubes with variable inner diameter and wall thickness are used as specimens. The qualitative and quantitative fluid structure phenomenon investigation are performed for both the continuous and pulsatile flow.
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Simulation of Compressible Flow in Time Dependent Domains
Prokopová, Jaroslava
This work is concerned with the numerical solution of compressible flow using finite element method in ALE (Arbitrary Lagrangian-Eulerian) formulation of the Navier-Stokes equations, their discretization in space by the discontinuous Galerkin method and introducing a semi-implicit linearized time stepping for the numerical solution of the complete problem. Some computational results are presented for flow in a channel with a moving wall.
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Dual-time stepping method applied to a numerical solution of unsteady incompressible flow with a vibrating profile
Honzátko, R. ; Horáček, Jaromír ; Kozel, K.
The paper presents numerical solution of two-dimensional incompressible flow in the interaction with a vibrating profile. The profile has two degrees of freedom. Mathematical model is represented either by the Euler equations in the case of inviscid flow or the Navier-Stokes equations in the case of viscous flow. Finite volume method is used as a discretization method. The dual-time stepping method is applied to unsteady simulations. This method provides a possibility to develop a time-accurate time-marching scheme for unsteady incompressible flows. Computational domain deformation due to the profile motion are treated using the Arbitrary Lagrangian-Eulerian method (ALE). Numerical schemes used for unsteady flow calculations are implemented in a form satisfying the geometric conservation law (GCL).
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Vibrace vyvolané proudem tekutiny 2008
Zolotarev, Igor ; Horáček, Jaromír
Flow-induced vibrations and noise continue to cause problems in a wide range of engineering applications, ranging from mechanical and aerospace engineering, civil engineering and ship and offshore structures to power generation and chemical processing. These proceedings bring together 139 papers dealing with a variety of topics relating to flow-induced vibration and noise, such as:vortex-induced vibration, vibration of heat-exchanger tube bundles,progress in fluid-structure interaction theory and CFD simulations, flow-sound interaction, biomechanics of voice and hearing, thermo-acoustic instabilities, vibration of hydraulic structures, gates, turbomachines nad piping systems. The contents of this publication constitute a „mixture“ of investigations by those working on the mechanisms of vibration and means of their alleviation, and studies by those in industry who draw on the present state of knowledge of these mechanisms to avoid or solve flow induced vibratin and noise problems in industrial and other applications.
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Analýza stability rovnovážné polohy a odezvy rotorů uložených v kapalinných ložiskách a majících kotouč ponořený v nesmáčivé kapalině
Zapoměl, Jaroslav
In a number of technological applications the rotors supported by fluid film bearings have the discs submerged in various liquids. Lateral vibration of such rotors is significantly influenced by their interaction with the medium in the surrounding space. A computer modelling method represents an important tool for investigation of their behaviour. The approach to analysis of vibration of small amplitudes of structures submerged in liquids is based on modification of the Navier Stokes equations leading to the Laplace one. The fluid film bearings are usually implemented into the computational models by means of nonlinear force couplings. The pressure distribution in the full oil film is governed by a Reynolds equation and in cavitated areas the pressure remains constant. The motion of a rotor supported by short hydrodynamic bearings, excited by imbalance forces, and having a disc submerged in inwettable liquid was investigated.
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