Number of found documents: 2925
Published from to

Finite element modeling of the signal propagation in a thin tube and comparison with experimental data
Kruisová, Alena; Kolman, Radek; Trnka, Jan; Mračko, Michal
2018 - English
In finite element modeling of wave propagation problems, both the spatial and temporal discretization lead to dispersion errors. It means that the phase velocity of propagated wave is related to its frequency. In framework of temporal-spatial dispersion analysis, the time step size for implicit time integration method based on the Newmark method is proposed for linear and quadratic serendipity plane finite elements. In this paper, we verify the theoretical dispersion analysis by elastic wave propagation in thin tube, where experimental results are known. Such time step size was used in finite element modeling of the stress wave propagating in this thin steel tube, the results of simulations were compared with experimental results. Keywords: wave propagation; finite element method; dispersion errors Available at various institutes of the ASCR
Finite element modeling of the signal propagation in a thin tube and comparison with experimental data

In finite element modeling of wave propagation problems, both the spatial and temporal discretization lead to dispersion errors. It means that the phase velocity of propagated wave is related to its ...

Kruisová, Alena; Kolman, Radek; Trnka, Jan; Mračko, Michal
Ústav termomechaniky, 2018

Experimental investigation of fault tolerant converter connected to unbalanced grid
Valouch, Viktor; Šimek, Petr; Škramlík, Jiří
2018 - English
A model of the three-phase voltage converter for simulation of its modes of operation in standard as wellas fault states is presented. The presented model can be used to simulate steady-states and also transients at dc and ac side of the grid-connected converter. Based on simulation, an algorithm was designed to identify and localize a fault in some phase of the three-phase converter. Rules how to modify hardware, and control and modulation strategies to hold the converter in operation after the fault are presented and tested. the algorithm was experimentally verified. Keywords: grid-connected converter; fault identification and localization; reconfiguration Available at various institutes of the ASCR
Experimental investigation of fault tolerant converter connected to unbalanced grid

A model of the three-phase voltage converter for simulation of its modes of operation in standard as wellas fault states is presented. The presented model can be used to simulate steady-states and ...

Valouch, Viktor; Šimek, Petr; Škramlík, Jiří
Ústav termomechaniky, 2018

Influence of excitation frequency and pulse width on blade vibration
Voronova, Evgeniya; Maturkanič, Dušan
2018 - English
The paper describes results of measuring of blade vibration characteristics excitation by one electromagnet at harmonic regime.The measurements were performed in the laboratory of rotational laser vibrometry originated at the Institute of Thermomechanics AS CR, v.v.i.\n Keywords: vibration; blade; laser; turbine Available at various institutes of the ASCR
Influence of excitation frequency and pulse width on blade vibration

The paper describes results of measuring of blade vibration characteristics excitation by one electromagnet at harmonic regime.The measurements were performed in the laboratory of rotational laser ...

Voronova, Evgeniya; Maturkanič, Dušan
Ústav termomechaniky, 2018

EXPERIMENTAL ANALYSIS OF BLADED WHEEL MODEL WITH TIE-BOSS COUPLINGS – STEADY AND ROTATIONAL STATES
Pešek, Luděk; Bula, Vítězslav; Šnábl, Pavel; Cibulka, Jan
2018 - English
Experimental modal analysis of the proposed model of bladed wheel with tie-boss couplings was performed for validation of thenumerical FE model. The pre-stresses in contacts were set and evaluated indirectly by the magnetic torque sensor. Then dynamical tests of bladed wheel under revolutions were performed. The\nelectromagnetic synchronized pulses were used for excitation of forced vibration of the wheel. The Campbell diagram of the wheel with prestressedcontacts was created from the measurement under revolutions. From the attenuation of resonant vibration of the wheel the dampingwas evaluated. Keywords: turbine blade; coupling; dry-friction Available at various institutes of the ASCR
EXPERIMENTAL ANALYSIS OF BLADED WHEEL MODEL WITH TIE-BOSS COUPLINGS – STEADY AND ROTATIONAL STATES

Experimental modal analysis of the proposed model of bladed wheel with tie-boss couplings was performed for validation of thenumerical FE model. The pre-stresses in contacts were set and evaluated ...

Pešek, Luděk; Bula, Vítězslav; Šnábl, Pavel; Cibulka, Jan
Ústav termomechaniky, 2018

Nonlinear ultrasonic porosimetry of 3D printed metallic parts
Převorovský, Zdeněk; Krofta, Josef; Kober, Jan; Kirschner, A.
2018 - English
Additive manufacturing process optimization requires a feedback from nondestructive testing (NDT) and evaluation. In this contribution are discussed NDT results obtained by nonlinear elastic wave spectroscopy methods to classify presence of defects in Ti-6Al-4V prismatic samples fabricated by electron beam printer. Quantitative calibration of porosity was realized by metallography. The best porosity classification results were obtained by nonlinear wave modulation spectroscopy with chirp excitation and by ESAM (Excitation Symmetry Analysis). Keywords: 3D printing of metals; nonlinear ultrasonics; porosity measurement Available at various institutes of the ASCR
Nonlinear ultrasonic porosimetry of 3D printed metallic parts

Additive manufacturing process optimization requires a feedback from nondestructive testing (NDT) and evaluation. In this contribution are discussed NDT results obtained by nonlinear elastic wave ...

Převorovský, Zdeněk; Krofta, Josef; Kober, Jan; Kirschner, A.
Ústav termomechaniky, 2018

Measurement of Turbulence in LP Part of the 1090 MW Steam Turbine
Antoš, Pavel; Uruba, Václav; Jonáš, Pavel; Procházka, Pavel P.; Skála, Vladislav; Hoznedl, M.; Sedlák, K.
2018 - English
The aim of the paper is to demonstrate a use of the hot-wire anemometry for measurement of turbulent fluctuation in a steam turbine. Measurement technique and used methods are presented in the paper. An experimental research was performed in the last stage of LP (lowpressure) part of the 1090 MW steam turbine in nuclear power-plant turbine. The last moving steel blade has a length of 1220 mm. The experiment was carried out by Institute of Thermomechanics of Czech Academy of Science (IT CAS) in cooperation with Doosan Škoda Power s.r.o. (DSPW), the manufacturer of the turbine. Keywords: turbulence; steam turbine; hot-wire anemometry Available at various institutes of the ASCR
Measurement of Turbulence in LP Part of the 1090 MW Steam Turbine

The aim of the paper is to demonstrate a use of the hot-wire anemometry for measurement of turbulent fluctuation in a steam turbine. Measurement technique and used methods are presented in the paper. ...

Antoš, Pavel; Uruba, Václav; Jonáš, Pavel; Procházka, Pavel P.; Skála, Vladislav; Hoznedl, M.; Sedlák, K.
Ústav termomechaniky, 2018

Proceedings of Topical Problems of Fluid Mechanics 2018
Šimurda, David; Bodnár, T.
2018 - English
The aim of the conference is to publish and to discuss the latest results of research in fluid mechanics. Keywords: experimental fluid mechanics; mathematical modelling; turbulence; stratified fluid; multiphase flow; superflow Available at various institutes of the ASCR
Proceedings of Topical Problems of Fluid Mechanics 2018

The aim of the conference is to publish and to discuss the latest results of research in fluid mechanics.

Šimurda, David; Bodnár, T.
Ústav termomechaniky, 2018

Generation of Intermittent Jet by Pulse-Modulated Synthetic Jets
Broučková, Zuzana
2018 - English
An axisymmetric air jet was excited using a pair of counter synthetic jets running in opposed direction. First, the control synthetic jets were measured alone. The driving signal was pulse modulated sinusoidal signal. After an adjustment, the primary axisymmetric jet was excited to the bifurcating mode, and its behavior was studied experimentally. For comparison purposes, a reference steady (unforced) jet from the same nozzle was also measured (Reynolds number was approximately 1300). The flow visualization and hot-wire anemometry techniques were used. Keywords: synthetic jet; pulse modulation; flow control Available at various institutes of the ASCR
Generation of Intermittent Jet by Pulse-Modulated Synthetic Jets

An axisymmetric air jet was excited using a pair of counter synthetic jets running in opposed direction. First, the control synthetic jets were measured alone. The driving signal was pulse modulated ...

Broučková, Zuzana
Ústav termomechaniky, 2018

The 2nd International Conference on Advanced Modelling of Wave Propagation in Solids
Kolman, Radek; Berezovski, A.; Kruisová, Alena
2018 - English
The 2nd International Conference on Advanced Modelling of Wave Propagation in Solids aims to bring together scientists and engineers with interest in advanced modelling of wave propagation in solids. The Conference on Advanced Modelling of Wave Propagation in Solids will concentrate on topics related to analytical, numerical and experimental studies of linear and non-linear waves in conventional, advanced and modern materials like metamaterials and auxetic materials, to strongly dispersive wave propagation in inhomogeneous solids and to waves in materials with microstructure, etc. Attention will also be devoted to up-to-date formulations of non-linear constitutive equations in the description of material response under thermomechanical loading, dynamic fracture and damage, phase transformations, shock waves, and to dissipative effects. The recent advances and properties of analytical and numerical approaches and strategies should also be discussed. The main purpose of the Conference on Advanced Modelling of Wave Propagation in Solids is to discuss novel and recent methods of wave propagation modelling and to consider expected credibility of results especially in cases when comparison with those of experiment is not available. Theoretical, computational as well as experimental contributions on the wave propagation are welcome. Keywords: wave propagation; advanced materials; numerical methods; experimental methods; dynamic behaviour of materials Available at various institutes of the ASCR
The 2nd International Conference on Advanced Modelling of Wave Propagation in Solids

The 2nd International Conference on Advanced Modelling of Wave Propagation in Solids aims to bring together scientists and engineers with interest in advanced modelling of wave propagation in solids. ...

Kolman, Radek; Berezovski, A.; Kruisová, Alena
Ústav termomechaniky, 2018

Spatial and temporal correlations in turbulent boundary layers
Jurčáková, Klára; Kellnerová, Radka
2018 - English
The experimental data from time-resolved particle image velocimetry measurement of the boundary-layer flows over various aerodynamically rough surfaces are presented. Temporal, spatial, and time-space correlation are analyzed and used for calculation of integral length and time scales. Temporal and spatial integral scales are connected via convection velocity. Taylor's hypothesis on frozen turbulence says that the convection velocity is equal to the local mean velocity. The experimental data shows that the convection velocity is larger than local mean velocity in the lower third of the boundary layer and greater in the upper two thirds. The cross-over line is higher over surfaces with higher roughness. Keywords: wind tunnel; time-resolved particle image velocimetry; aerodynamically rough surfaces; integral length scales Available at various institutes of the ASCR
Spatial and temporal correlations in turbulent boundary layers

The experimental data from time-resolved particle image velocimetry measurement of the boundary-layer flows over various aerodynamically rough surfaces are presented. Temporal, spatial, and time-space ...

Jurčáková, Klára; Kellnerová, Radka
Ústav termomechaniky, 2018

About project

NRGL provides central access to information on grey literature produced in the Czech Republic in the fields of science, research and education. You can find more information about grey literature and NRGL at service web

Send your suggestions and comments to nusl@techlib.cz

Provider

http://www.techlib.cz

Facebook

Other bases