Počet nalezených dokumentů: 1835
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Model order reduction for particle-laden flows: systems with rotations and discrete transport operators
Kovárnová, A.; Isoz, Martin
2023 - anglický
In the present work, we concentrate on particle-laden flows as an example of industry-relevant transport-dominated systems. Our previously-developed framework for data-driven model order reduction (MOR) of such systems, the shifted proper orthogonal decomposition with interpolation via artificial neural networks, is further extended by improving the handling of general transport operators. First, even with intrusive MOR approaches, the underlying numerical solvers can provide only discrete realizations of transports linked to the movement of individual particles in the system. On the other hand, our MOR methodology requires continuous transport operators. Thus, the original framework was extended by the possibility to reconstruct continuous approximations of known discrete transports via another artificial neural network. Second, the treatment of rotation-comprising transports was significantly improved. Klíčová slova: model order reduction; shifted POD; artificial neural networks; CFD-DEM; Open- FOAM Dokument je dostupný na externích webových stránkách.
Model order reduction for particle-laden flows: systems with rotations and discrete transport operators

In the present work, we concentrate on particle-laden flows as an example of industry-relevant transport-dominated systems. Our previously-developed framework for data-driven model order reduction ...

Kovárnová, A.; Isoz, Martin
Ústav termomechaniky, 2023

Aerodynamic Measurements on Subsonic Compressor Blade Cascades KR-D-7 and KR-D-8
Šimurda, David; Hála, Jindřich; Luxa, Martin; Radnic, Tomáš
2023 - anglický
This report contains results and evaluation of aerodynamic measurements conducted on two variant subsonic compressor blade cascades with MCA profile (KR-D-7) and DCA profile (KR-D-8) at transonic flow regimes. Klíčová slova: compressor blade cascade; experiment; transonic flow; subsonic flow; MCA profile; DCA profile Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Aerodynamic Measurements on Subsonic Compressor Blade Cascades KR-D-7 and KR-D-8

This report contains results and evaluation of aerodynamic measurements conducted on two variant subsonic compressor blade cascades with MCA profile (KR-D-7) and DCA profile (KR-D-8) at transonic flow ...

Šimurda, David; Hála, Jindřich; Luxa, Martin; Radnic, Tomáš
Ústav termomechaniky, 2023

Aerodynamic Measurements on Transonic Compressor Blade Cascades KR-D-9 and KR-D-10
Šimurda, David; Hála, Jindřich; Luxa, Martin
2023 - anglický
This report contains results and evaluation of aerodynamic measurements conducted on two variant transonic compressor blade cascades with MCA profile (KR-D-10) and DCA profile (KR-D-9) at transonic flow regimes. Klíčová slova: compressor blade cascade; experiment; transonic flow; MCA profile; DCA profile Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Aerodynamic Measurements on Transonic Compressor Blade Cascades KR-D-9 and KR-D-10

This report contains results and evaluation of aerodynamic measurements conducted on two variant transonic compressor blade cascades with MCA profile (KR-D-10) and DCA profile (KR-D-9) at transonic ...

Šimurda, David; Hála, Jindřich; Luxa, Martin
Ústav termomechaniky, 2023

Dynamics of a cantilever beam with piezoelectric sensor: Parameter identification
Cimrman, Robert; Kolman, Radek; Musil, Ladislav; Kotek, Vojtěch; Kylar, Jaromír
2023 - anglický
The piezoelectric materials are electroactive materials often applied for real-time sensing or structural health monitoring, both important research topics in dynamics. Mathematical models of such structures have to allow also for the external electrical circuits and contain several material parameters that need to be identified from experiments. We present a model of a simple experiment involving dynamics of a cantilever beam with an attached piezoelectric sensor excited by a suddenly removed weight. The external circuit can be taken into account as having either a finite or infinite resistance. We also outline the parameter identification procedure based on automatic differentiation and present the experimental and numerical results. Klíčová slova: finite element method; piezo-electricity; floating potential; dynamic simulation; parameter identification Dokument je dostupný na externích webových stránkách.
Dynamics of a cantilever beam with piezoelectric sensor: Parameter identification

The piezoelectric materials are electroactive materials often applied for real-time sensing or structural health monitoring, both important research topics in dynamics. Mathematical models of such ...

Cimrman, Robert; Kolman, Radek; Musil, Ladislav; Kotek, Vojtěch; Kylar, Jaromír
Ústav termomechaniky, 2023

Development of autonomous experimental system to analyse yield surfaces distortion due to multiaxial ratcheting
Svárovský, Jiří; Parma, Slavomír; Štefan, Jan; Ciocanel, C.; Feigenbaum, H. P.; Marek, René; Klepač, Vilém; Plešek, Jiří
2023 - anglický
Multiaxial ratcheting is a failure mode of structures characterized by the accumulation of plastic strain due to cyclic loading. Despite several models having been developed to predict multiaxial ratcheting, they often fail when validated with experimental data collected under a wide array of loading conditions. In this study, an experimental setup was developed and an autonomous testing procedure was used to experimentally analyze the evolution of the yield surface shape due to cyclic biaxial loading. Thin-walled tubular test specimens were made of 304L steel with a diameter of 40mm and underwent axial-torsional testing using the Instron 8852 system. The total axial strain was increased from 0 to 1% while the total shear strain underwent 5 cycles with the strain amplitude of 0.5% and the mean strain of 0.5%. Three yield surfaces were measured after the straining sequence was completed. Results showed strong directional distortional hardening and good agreement between the flow vectors and the normals to the yield surface, lending support to the associative flow rule. Klíčová slova: yield surface distortion; strain hardening; multiaxial ratcheting; flow rule Dokument je dostupný na externích webových stránkách.
Development of autonomous experimental system to analyse yield surfaces distortion due to multiaxial ratcheting

Multiaxial ratcheting is a failure mode of structures characterized by the accumulation of plastic strain due to cyclic loading. Despite several models having been developed to predict multiaxial ...

Svárovský, Jiří; Parma, Slavomír; Štefan, Jan; Ciocanel, C.; Feigenbaum, H. P.; Marek, René; Klepač, Vilém; Plešek, Jiří
Ústav termomechaniky, 2023

Numerical minimization of energy functionals in continuum mechanics using hp-FEM in MATLAB
Moskovka, Alexej; Frost, Miroslav; Valdman, Jan
2023 - anglický
Many processes in mechanics and thermodynamics can be formulated as a minimization of a particular energy functional. The finite element method can be used for an approximation of such functionals in a finite-dimensional subspace. Consequently, the numerical minimization methods (such as quasi-Newton and trust region) can be used to find a minimum of the functional. Vectorization techniques used for the evaluation of the energy together with the assembly of discrete energy gradient and Hessian sparsity are crucial for evaluation times. A particular model simulating the deformation of a Neo-Hookean solid body is solved in this contribution by minimizing the corresponding energy functional. We implement both P1 and rectangular hp-finite elements and compare their efficiency with respect to degrees of freedom and evaluation times. Klíčová slova: hp-FEM; energy functionals; numerical minimization Dokument je dostupný na externích webových stránkách.
Numerical minimization of energy functionals in continuum mechanics using hp-FEM in MATLAB

Many processes in mechanics and thermodynamics can be formulated as a minimization of a particular energy functional. The finite element method can be used for an approximation of such functionals in ...

Moskovka, Alexej; Frost, Miroslav; Valdman, Jan
Ústav termomechaniky, 2023

Self-balancing of vertical disc rotors supported by contactless bearings
Zapoměl, Jaroslav; Kozánek, Jan; Košina, Jan
2023 - anglický
Article discusses the self-balancing of the vertical disc rotors supported by contactless bearings on principle of diamagnetic levitation. There are three possibilities of contactless supports: permanent magnet levitation with the help of bismuth, graphite and pyrolitic graphite. Klíčová slova: self balancing; vertical disc rotors; contactless bearings Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Self-balancing of vertical disc rotors supported by contactless bearings

Article discusses the self-balancing of the vertical disc rotors supported by contactless bearings on principle of diamagnetic levitation. There are three possibilities of contactless supports: ...

Zapoměl, Jaroslav; Kozánek, Jan; Košina, Jan
Ústav termomechaniky, 2023

Dynamics of a cantilever beam with piezoelectric sensor: Finite element modeling
Cimrman, Robert; Kolman, Radek; Musil, Ladislav; Kotek, Vojtěch; Kylar, Jaromír
2023 - anglický
An elastodynamical model of a cantilever beam coupled with a piezoelectric sensor is introduced and its discretization using the finite element method is presented. The mathematical model includes additional terms that enforce the floating potential boundary condition for keeping a constant charge on an electrode of the sensor. The behaviour of the model is illustrated using a numerical example corresponding to an experimental setup, where vibrations of the beam and the potential on the sensor are measured. Klíčová slova: finite element method; piezo-electricity; floating potential; dynamic simulation Dokument je dostupný na externích webových stránkách.
Dynamics of a cantilever beam with piezoelectric sensor: Finite element modeling

An elastodynamical model of a cantilever beam coupled with a piezoelectric sensor is introduced and its discretization using the finite element method is presented. The mathematical model includes ...

Cimrman, Robert; Kolman, Radek; Musil, Ladislav; Kotek, Vojtěch; Kylar, Jaromír
Ústav termomechaniky, 2023

Topical Problems of Fluid Mechanics 2023
Šimurda, David; Bodnár, T.
2023 - anglický
Proceedings contain collection of papers presented during the conference Topical Problems of Fluid Mechanics 2023. Majority of papers is concerned with numerical simulations covering wide range of applications in fluid mechanics.\n Klíčová slova: experimental fluid mechanics; mathematical modelling; CFD; turbulence; stratified fluid; multiphase flow; vortex structures; supersonic flow Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Topical Problems of Fluid Mechanics 2023

Proceedings contain collection of papers presented during the conference Topical Problems of Fluid Mechanics 2023. Majority of papers is concerned with numerical simulations covering wide range of ...

Šimurda, David; Bodnár, T.
Ústav termomechaniky, 2023

Direct construction of reciprocal mass matrix and higher order fininite element method
Cimrman, Robert; Kolman, Radek; González, J. A.; Park, K. C.
2023 - anglický
When solving dynamical problems of computational mechanics, such as contact-impact problems or cases involving complex structures under fast loading conditions, explicit time-stepping algorithms are usually preferred over implicit ones. The explicit schemes are normally combined with the lumped (diagonal) mass matrix so that the calculations are efficient and moreover dispersion errors in wave propagation are partially eliminated. As an alternative to lumping with advantageous properties, the reciprocal mass matrix is an inverse mass matrix that has the same sparsity structure as the original consistent mass matrix, preserves the total mass, captures well the desired frequency spectrum and leads thus to efficient and accurate calculations. In the contribution we comment on the usability of the reciprocal mass matrix in connection with higher order FEM. Klíčová slova: higher-order finite element method; reciprocal mass matrix; transient problems; explicit time integration; lumping process Dokument je dostupný na externích webových stránkách.
Direct construction of reciprocal mass matrix and higher order fininite element method

When solving dynamical problems of computational mechanics, such as contact-impact problems or cases involving complex structures under fast loading conditions, explicit time-stepping algorithms are ...

Cimrman, Robert; Kolman, Radek; González, J. A.; Park, K. C.
Ústav termomechaniky, 2023

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