Number of found documents: 2718
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Simulation of heterogeneously-catalyzed non-isothermal reactive flow in industrial packed beds
Hlavatý, Tomáš; Isoz, Martin; Khýr, M.
2023 - English
Packed bed reactors are the most frequently used devices to perform heterogeneously catalyzed reactions on industrial scales. An industrial real-life heterogeneous catalysis is complex process that combines fully three-dimensional mass, momentum and energy transport on several scales. In the present work, we leverage our previously developed CFD solver for non-isothermal heterogeneously catalyzed reactive flow based on the finite volume method and couple it with our\nin-house DEM-based method for preparation of random packed beds. The resulting framework is verified in the simplified cases against available analytical solutions and correlations and is used to study an industrially-relevant case of ethylene oxychlorination performed in a tubular packed bed comprising CuCl2-coated catalyst carrying particles. In particular, we compare properties of three different industrially used catalyst carrying particles: Raschig rings, Reformax, and Wagon wheels Keywords: CFD; OpenFOAM; non-isothermal flow Available in a digital repository NRGL
Simulation of heterogeneously-catalyzed non-isothermal reactive flow in industrial packed beds

Packed bed reactors are the most frequently used devices to perform heterogeneously catalyzed reactions on industrial scales. An industrial real-life heterogeneous catalysis is complex process that ...

Hlavatý, Tomáš; Isoz, Martin; Khýr, M.
Ústav termomechaniky, 2023

Implementation of wall functions into a hybrid fictitious domain-immersed boundary method
Kubíčková, Lucie; Isoz, Martin
2023 - English
Hybrid fictitious domain-immersed boundary method (HFDIB) is a simulation approach used in computational fluid dynamics. The approach avoids usage of complex geometry-conforming computational domains. Instead, a simple domain is used and the geometry is projected onto it by a scalar field and adjustment of governing equations. Hence, the time spent on mesh generation is substantially reduced. It is advantageous to use the HFDIB in geometry optimizations where it allows for a massive optimization speed-up. Nevertheless, there is a problem with simulation of the fluid behavior in the boundary layer in the vicinity of the immersed walls. Especially, in simulation of highly turbulent flows, where the boundary layer is very thin and the usage of finer mesh is unaffordable. In this work, we aim to solve this problem by implementation of Reynolds averaged turbulence models in our custom HFDIB variant. In particular, we implemented the k-ω turbulence model and blended wall functions for closure variables and velocity. Keywords: wall functions; immersed boundary method; CFD; RAS Fulltext is available at external website.
Implementation of wall functions into a hybrid fictitious domain-immersed boundary method

Hybrid fictitious domain-immersed boundary method (HFDIB) is a simulation approach used in computational fluid dynamics. The approach avoids usage of complex geometry-conforming computational domains. ...

Kubíčková, Lucie; Isoz, Martin
Ústav termomechaniky, 2023

Model order reduction of transport-dominated systems with rotations using shifted proper orthogonal decomposition and artificial neural networks
Kovárnová, A.; Isoz, Martin
2023 - English
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. Keywords: model order reduction; CFD; shifted POD Fulltext is available at external website.
Model order reduction of transport-dominated systems with rotations using shifted proper orthogonal decomposition and artificial neural networks

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

Development, validation, and application of a solver for non-isothermal non-adiabatic packed bed reactors
Hlavatý, Tomáš; Isoz, Martin; Khýr, M.
2023 - English
Packed bed reactors are the most frequently used devices to perform heterogeneously catalyzed reactions on industrial scales. The main contribution of our work is the development of a numerical model applicable to simulations of such reactors. The developed model is based on the finite volume method, couples the momentum, mass and energy balances, and is free of any empirical closures. As such, the solver falls into the domain of the direct numerical simulation. In the talk, we will (i) present the new solver fundamental working principles, (ii) report on the verication of each of the solver components against existing literature data and (iii) demonstrate an application of the solver on an industrially relevant case of ethylene oxichlorination performed in a tubular reactor packed with Raschig rings coated by CuCl2 catalyst. Keywords: CFD; oxichlorination; heterogenous catalysis Fulltext is available at external website.
Development, validation, and application of a solver for non-isothermal non-adiabatic packed bed reactors

Packed bed reactors are the most frequently used devices to perform heterogeneously catalyzed reactions on industrial scales. The main contribution of our work is the development of a numerical model ...

Hlavatý, Tomáš; Isoz, Martin; Khýr, M.
Ústav termomechaniky, 2023

A short study on self-balancing of vertical rotors mounted in passive contactless bearings
Zapoměl, Jaroslav; Kozánek, Jan
2023 - English
Energy losses and wear of the support elements of high-speed rotors can be reduced by mounting the rotors in stable passive contactless bearings, the operation of which is based on magnetic levitation. The goal of the conducted research was to investigate applicability of self­balancing device added to vertical rotors supported by bearings showing low stiffness and damping, which is a specific property of passive magnetic bearings. This paper deals with applicability and efficiency of self-balancing devices added to vertical rotors supported by bearings having very low stiffness and damping, which corresponds to the properties of magnetic frictionless bearings. Keywords: self-balancing of rotors; passive contactless bearings; the influence of external damping Available at various institutes of the ASCR
A short study on self-balancing of vertical rotors mounted in passive contactless bearings

Energy losses and wear of the support elements of high-speed rotors can be reduced by mounting the rotors in stable passive contactless bearings, the operation of which is based on magnetic ...

Zapoměl, Jaroslav; Kozánek, Jan
Ústav termomechaniky, 2023

Dynamic tensile experiments of hard rubber on instron test machine under finite deformations
Šulc, Petr; Pešek, Luděk; Bula, Vítězslav; Šnábl, Pavel
2023 - English
This paper deals with the first experimental tests of hard rubbers under tensile harmonic loading on the axial-torsional servohydraulic Instron 8852 test machine. The objective of these experiments on cylindrical rubber specimens on this machine is to obtain stress-strain curves of rubber specimens, first considering uniaxial finite longitudinal strains for a single load cycle. Next, the hysteresis loops and their skeleton curves are compared for two selected strain measures as a function of their conjugate stress. It is shown how to obtain the dependence between elongation in the axial direction and constriction in the radial direction, which is used to determine the Cauchy stress in this configuration. Keywords: uniaxial harmonic loading; finite deformation; second Piola-Kirchhoff stress; hysteresis loop; Green-Lagrange strain tensor Available at various institutes of the ASCR
Dynamic tensile experiments of hard rubber on instron test machine under finite deformations

This paper deals with the first experimental tests of hard rubbers under tensile harmonic loading on the axial-torsional servohydraulic Instron 8852 test machine. The objective of these experiments on ...

Šulc, Petr; Pešek, Luděk; Bula, Vítězslav; Šnábl, Pavel
Ústav termomechaniky, 2023

Deep learning methods for the acoustic emission methods to evaluate an onset of plastic straining
Parma, Slavomír; Kovanda, Martin; Chlada, Milan; Štefan, Jan; Kober, Jan; Feigenbaum, H. P.; Plešek, Jiří
2023 - English
Development of phenomenological plasticity models, hardening rules, and plasticity theories relies on experimental data of plastic straining. The experimental data are usually measured as the stress–strain response of the material being loaded and do not provide any clues or information about the local response of\nmaterial. In this paper, we analyze the plastic deformation of the material using the acoustic emission method and current state-of-the-art neural network models such as the InceptionTime architecture. Keywords: metal plasticity; strain hardening; acoustic emission; neural networks Fulltext is available at external website.
Deep learning methods for the acoustic emission methods to evaluate an onset of plastic straining

Development of phenomenological plasticity models, hardening rules, and plasticity theories relies on experimental data of plastic straining. The experimental data are usually measured as the ...

Parma, Slavomír; Kovanda, Martin; Chlada, Milan; Štefan, Jan; Kober, Jan; Feigenbaum, H. P.; Plešek, Jiří
Ústav termomechaniky, 2023

Model order reduction for particle-laden flows: systems with rotations and discrete transport operators
Kovárnová, A.; Isoz, Martin
2023 - English
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. Keywords: model order reduction; shifted POD; artificial neural networks; CFD-DEM; Open- FOAM Fulltext is available at external website.
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

Dynamics of a cantilever beam with piezoelectric sensor: Finite element modeling
Cimrman, Robert; Kolman, Radek; Musil, Ladislav; Kotek, Vojtěch; Kylar, Jaromír
2023 - English
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. Keywords: finite element method; piezo-electricity; floating potential; dynamic simulation Fulltext is available at external website.
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

Dynamics of a cantilever beam with piezoelectric sensor: Parameter identification
Cimrman, Robert; Kolman, Radek; Musil, Ladislav; Kotek, Vojtěch; Kylar, Jaromír
2023 - English
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. Keywords: finite element method; piezo-electricity; floating potential; dynamic simulation; parameter identification Fulltext is available at external website.
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

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