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Localized formulation of bipenalty method in contact-impact problems
Kolman, Radek; González, J. A.; Dvořák, Radim; Kopačka, Ján; Park, K.C.
2022 - English
Often, the finite element method together with direct time integration is used for modelling of contact-impact problems of bodies. For direct time integration, the implicit or explicit time stepping are gen-\nerally employed. It is well known that the time step size in explicit time integration is limited by the stability limit. Further, the trouble comes with the task of impact of bodies with different critical time step sizes for each body in contact. In this case, this numerical strategy based on explicit time stepping with the same time step size for both bodies is not effective and is not accurate due to the dispersion behaviour and spurious stress oscillations. For that reason, a numerical methodology, which allows independent time stepping for each body with its time step size, is needed to develop. In this paper, we introduce the localized variant of the bipenalty method in contact-impact problems with the governing equations derived based on the Hamilton’s principle. The localized bipenalty method is applied into the impact problems of bars as an one-dimensional problem. The definition of localized gaps is presented and applied into the full concept of the localized bipenalty method.
Keywords:
contact-impact problem; explicit time integration; bipenalty formulation; ocalized lagrange multipliers; stability analysis
Available at various institutes of the ASCR
Localized formulation of bipenalty method in contact-impact problems
Often, the finite element method together with direct time integration is used for modelling of contact-impact problems of bodies. For direct time integration, the implicit or explicit time stepping ...
Aspects of Dosage from Short and Long Duration Emissions
Robins, A.; Hayden, P.; Gallacher, D.; Pace, S.; Chaloupecká, Hana
2022 - English
The objectives of this work were to use wind tunnel concentration measurements to describe the structure of dispersing clouds from an elevated source in a deep turbulent boundary layer and to develop scaling rules that reduce the results to a universal form. The experiments were carried out in the EnFlo meteorological wind tunnel at the University of Surrey. Ensembles of between 100 and 200\nrepeat emissions were used, emission durations between 0.067 and 1.02s and a reference flow speed of 2ms-1. The fetch studied extended to about six source heights downwind (about two boundary layer depths). The structure of the evolving clouds was analysed to determine time of flight, along-wind spread and dosage and to compare the dosage behaviour with the concentration field in a plume from the same source. This illustrated how the two were related and how cloud dosage statistics (mean and\nstandard deviation) could be derived from plume data. It also demonstrated that much larger ensembles were required to reduce the statistical uncertainty in the mean cloud properties. The next steps involve testing these conclusions in a wider range of flow and dispersion conditions, in the presence of obstacles or complex urban areas.
Keywords:
wind tunnel; dose; dosage; gas releases
Available at various institutes of the ASCR
Aspects of Dosage from Short and Long Duration Emissions
The objectives of this work were to use wind tunnel concentration measurements to describe the structure of dispersing clouds from an elevated source in a deep turbulent boundary layer and to develop ...
Autobusy s vodíkovým a elektrickým pohonem v České republice a ve světě (2000-2022)
Gruber, Jan; Bouška, Jindřich; Brtna, D.; Janovec, Jiří
2022 - Czech
Zpráva shrnuje údaje o využití vodíkových autobusů v České republice, zemích Evropské unie a částečně též ostatních zemích světa. Zahrnuje jak historické a již ukončené projekty, tak i projekty běžící a plánované v blízké budoucnosti. Zpráva popisuje, shrnuje a srovnává dostupné parametry těchto vodíkových autobusů, se zaměřením na autobusy využívané pro městskou hromadnou dopravu. Zpráva také pro srovnání obsahuje předběžné výsledky simulací spotřeby vodíkového autobusu v modelu vyvíjeném v rámci projektu ve výpočetním a simulačním prostředí MATLAB/Simulink. The report summarizes parameters of electrobuses and hydrogen buses in the Czech republic, in the EU and to same extent also in other countries. In includes both historical, already finished projects and current or planned projects in the near future. The report describes and compares available parameters of these hydrogen buses, focusing on the mass-transit city buses. The report also includes preliminary results of simulations of hydrogen bus consumption. These were simulated in the model being developed in MATLAB/Simulink environment.
Keywords:
bus; electrobus; fuel celll; hydrogen; mass transit
Available at various institutes of the ASCR
Autobusy s vodíkovým a elektrickým pohonem v České republice a ve světě (2000-2022)
Zpráva shrnuje údaje o využití vodíkových autobusů v České republice, zemích Evropské unie a částečně též ostatních zemích světa. Zahrnuje jak historické a již ukončené projekty, tak i projekty běžící ...
V6: Zpráva popisující funkční vzorek NEMENUS
Štefan, Jan; Joch, Jaroslav; Převorovský, Zdeněk; Gabriel, Dušan; Krofta, Josef; Chlada, Milan; Kober, Jan; Masák, Jan; Materna, A.; Kovářík, O.; Čech, J.
2022 - Czech
Výzkumná zpráva je součástí závazného výstupu V6: FUNKČNÍ VZOREK projektu TAČR TK01030108: Inovativní posuzování bezpečnosti jaderných elektráren na základě nových technologií SHM a návazných procedur - NEMENUS (NEw MEthods for NUclear Safety). Zpráva podává úplný technický popis sestrojeného reprezentativního funkčního vzorku, tedy „reprezentativního SHM modelu“, a popis procesu čtyřletého experimentálního vývoje RFV. This research report is an integral part of mandatory output V6: FUNCTIONAL SPECIMEN of project TAČR TK01030108: Innovative methods for nuclear plant safety evaluation based on SHM technologies and related procedures - NEMENUS (NEw MEthods for NUclear Safety). The report presents full technical description of the elaborated representative functional specimen (the representative SHM model) and the description of a four-year experimental program.
Keywords:
structural health monitoring; nondestructive testing; fatigue testing
Available at various institutes of the ASCR
V6: Zpráva popisující funkční vzorek NEMENUS
Výzkumná zpráva je součástí závazného výstupu V6: FUNKČNÍ VZOREK projektu TAČR TK01030108: Inovativní posuzování bezpečnosti jaderných elektráren na základě nových technologií SHM a návazných procedur ...
Ochranné obvody měničů PF
Hauptmann, R.; Kokeš, Petr
2022 - Czech
Zpráva obsahuje popis a výsledky simulací obvodů, které slouží jako ochrany proti poškození hlavního silového obvodu napájení vinutí PF (Poloidal Field) tokamaku v případě vzniku havarijních stavů. Za normálního provozního stavu ochranné obvody činnost silových obvodů neovlivňují. Ochranné obvody tvoří samostatný systém, který je funkčně nezávislý na obvodech měničů a jejích řízení. Charakter funkce tohoto systému je koncipován jako bezpečnostní obvod – závada ochranného systému vede vždy k bezpečnému odstavení zařízení. Description and results of numerical simulations of circuits, which provide damage protection of the main power supply circuit for tokamak PF (Poloidal Field) coils under emergency conditions, is presented. In case of normal operation the protection circuits do not affect operation of the power supply circuitry. The protection circuits represent a separate system which is functionally independent of circuits and control of power converters. Functinality of this system is designed as a safety circuit - a fault of the protection system always causes safety shut-down of the device.
Keywords:
tokamak; PF coils; power converter
Available at various institutes of the ASCR
Ochranné obvody měničů PF
Zpráva obsahuje popis a výsledky simulací obvodů, které slouží jako ochrany proti poškození hlavního silového obvodu napájení vinutí PF (Poloidal Field) tokamaku v případě vzniku havarijních stavů. Za ...
Numerical simulations of aeroelastic instabilities in turbine blade cascade by modified Van der Pol model at running excitation
Pešek, Luděk; Šnábl, Pavel; Prasad, Chandra Shekhar; Delanney, Y.
2022 - English
Apart from rotary test rig for evaluation of structural dynamics of the bladed wheels, the control flutter experiments has been performed on the linear cascade model in the subsonic wind tunnel in the Institute of Thermomechanics, of CAS, in Prague. These experiments are aimed at stability evaluation of the cascade at running waves or at stability limit testing by flow speed changes or by force impulses of blades. The onset of flutter and its spreading in the cascade are observed, too. The linear cascade model consists of five NACA010 blades. All the blades can be separately excited with electromagnetic torque excitation mechanism and all of them are instrumented to measure the aerodynamic moments which can be used to calculate the aerodynamic work. A more details about the linear blade cascade experimental set up can be found in [1-2]. To predict a dynamic behaviour in the blade cascade, we have been dealing with simplified theoretical modelling of the aeroelastic instability in turbine blade cascade [3-5]. Due to the application of the reduced cascade model consisting of simple elements – springs, rigid bodies, linear dampers – and aeroelastic forces introduced by analytical Van der Pol model, it facilitates to study the dangerous states of vibration of such complicated turbine parts [6-9]. This study is aimed at examination of aeroelastic instabilities of 10-blade cascade at running excitation that arises due to the wakes flowing from stator the blades to the rotating blades. They cause forced excitation in the narrow frequency range.
Keywords:
rotary test; structural dynamics; bladed wheels
Available at various institutes of the ASCR
Numerical simulations of aeroelastic instabilities in turbine blade cascade by modified Van der Pol model at running excitation
Apart from rotary test rig for evaluation of structural dynamics of the bladed wheels, the control flutter experiments has been performed on the linear cascade model in the subsonic wind tunnel in ...
Estimation of damping in human vocal folds vibration: measurements in vivo and on model
Horáček, Jaromír; Radolf, Vojtěch; Bula, Vítězslav; Košina, Jan; Geneid, A.; Laukkanen, A. M.
2022 - English
This study investigates the biomechanics of the end-part of phonation, i.e. the so-called phonation offset, experimentally. This information of vocal folds damping is important for testing and further development of mathematical modelling of phonation. The measurements of the damping ratio, based on high-speed videolaryngoscopic registrations, were realized in vivo on a male subject and in vitro using an originally developed silicon replica of the human vocal folds. In both cases the results show remarkable decrease of vibration frequency of the vocal folds and increase of damping ratio D in the phonation offset limiting to the values D=0.12 in vivo measurement and D=0.11 in vitro measurement. The results for vocal folds’ damping are in good agreement with previous measurements performed in humans using different methods.
Keywords:
phonation offset; high-speed videolaryngoscopy
Available at various institutes of the ASCR
Estimation of damping in human vocal folds vibration: measurements in vivo and on model
This study investigates the biomechanics of the end-part of phonation, i.e. the so-called phonation offset, experimentally. This information of vocal folds damping is important for testing and further ...
Experimental investigation of the frequency-modal properties of the measuring container for LUNA mission
Zolotarev, Igor; Bula, Vítězslav; Šnábl, Pavel; Snížek, Jan; Souček, Jan
2022 - English
This paper continues investigations of the measuring equipment for space missions. The frequency-modal properties of the measuring container for LUNA mission were obtained by experimental investigation.
Keywords:
modal analysis; natural frequencies; modes of vibration
Available at various institutes of the ASCR
Experimental investigation of the frequency-modal properties of the measuring container for LUNA mission
This paper continues investigations of the measuring equipment for space missions. The frequency-modal properties of the measuring container for LUNA mission were obtained by experimental ...
Survey of the use of propane as refrigerant R290 in cooling circuits and heat pumps
Aminian, Ali; Prokopová, Olga; Vinš, Václav
2022 - English
The technical report presents a review on the application of propane as refrigerant R290 in cooling circuits and heat pumps (HVAC). Safety risks of R290 used in HVAC are addressed according to ANSI/ASHRAE and EN standards. Comparison of thermophysical properties of propane with other refrigerants, solubility and miscibility of propane in compressor oils and heat transfer in condenser and evaporator are discussed. The main aim of the study is to provide an overview about the potential use of propane in the cooling circuit and heat pump for the hydrogen bus developed by the SOR Libchavy company.
Keywords:
cooling circuit; heat pump; hydrogen bus; refrigerant
Available at various institutes of the ASCR
Survey of the use of propane as refrigerant R290 in cooling circuits and heat pumps
The technical report presents a review on the application of propane as refrigerant R290 in cooling circuits and heat pumps (HVAC). Safety risks of R290 used in HVAC are addressed according to ...
Identification of material constants of rubber damping segments by modal analysis for railway rubber-resilient wheels
Šulc, Petr; Šnábl, Pavel; Pešek, Luděk; Bula, Vítězslav
2022 - English
In this paper, an experimental and numerical modal analysis is described to assess two rubber compounds for the damping segments of a railway wheel. The subject of this comparison is materiál parameters such as Young’s modulus and loss factor for both compounds in the frequency range up to 6.5 kHz. From this comparison, an idea of the damping, stiffness and durability of these rubber segment materials inside these wheels is obtained.
Keywords:
modal analysis; rubber; railway wheel; damping segment
Available at various institutes of the ASCR
Identification of material constants of rubber damping segments by modal analysis for railway rubber-resilient wheels
In this paper, an experimental and numerical modal analysis is described to assess two rubber compounds for the damping segments of a railway wheel. The subject of this comparison is materiál ...
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