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Improving computational efficiency of contact solution in fully resolved CFD-DEM simulations with arbitrarily-shaped solids
Studeník, Ondřej; Kotouč Šourek, M.; Isoz, Martin
2023 - anglický
The abundance of industrial processes containing both solid and liquid phases generate demand for fully resolved models allowing for detailed analysis and optimization of these processes. An established approach providing such models is based using a variant of an immersed boundary method to couple the computational fluid dynamics (CFD) and discrete element method (DEM). In the talk, we will present our custom and monolithic implementation of a fully-resolved CFDDEM solver and concentrate on the intricacies of solving contact between two arbitrarily-shaped solids. We shall propose an efficient contact treatment based on the concept of a virtual mesh, which provides the mesh resolution required by DEM through dividing the space around the contact point in a finite volume fashion without any changes to the CFD mesh itself. A substantial part of the talk will devoted to the parallelization of the contact solution, especially in the context of the domain decomposition method imposed by the CFD solver.
Klíčová slova:
CFD; DEM; virtual mesh
Dokument je dostupný na externích webových stránkách.
Improving computational efficiency of contact solution in fully resolved CFD-DEM simulations with arbitrarily-shaped solids
The abundance of industrial processes containing both solid and liquid phases generate demand for fully resolved models allowing for detailed analysis and optimization of these processes. An ...
Ceramic protection of anti-corrosion layers of 3-glycidyloxypropyl-triethoxysilane on steel
Pokorný, P.; Prodanović, N.; Janata, Marek; Brožek, Vlastimil
2023 - anglický
There are various variations on the problem of steel reinforcement bond strength in concrete. Along with geometrical considerations, corrosion performance of steels with varying chemical compositions in interaction with variable chemical compositions of concrete are crucial. One approach is to cover steel surfaces with organosilane compounds, which increases the reinforcement resistance to corrosion in both acidic and alkaline conditions but, on the other hand, may weaken the reinforcement bond strength on concrete. The issue is resolved by intentionally forming a thin-walled, highly adhering corundum layer that is highly porous and impregnated with 3-glycidyloxypropyltriethoxysilane. This procedure also includes testing the adhesion properties between the ceramic and the metal and the cement prior to conducting a corrosion test in a chloride environment.
Klíčová slova:
steel; concrete; ceramics
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Ceramic protection of anti-corrosion layers of 3-glycidyloxypropyl-triethoxysilane on steel
There are various variations on the problem of steel reinforcement bond strength in concrete. Along with geometrical considerations, corrosion performance of steels with varying chemical compositions ...
On the development of a numerical model for the simulation of air flow in the human airways
Lancmanová, Anna; Bodnár, Tomáš; Sequeira, A.
2023 - anglický
This contribution reports on an ongoing study focusing on reduced order models for incompressible viscous fluid flow in two dimensional channels. A finite difference solver was developed using a simple implementation of the immersed boundary method to represent the channel geometry. The solver was validated for unsteady flow by comparing the obtained two-dimensional numerical solutions with analytical profiles computed from the Womersley solution. Finally the 2D model was coupled to a simple 1D extension simulating the flow in axisymmetric elastic vessel (tube). Some of the coupling principles and implementation issues are discussed in detail.
Klíčová slova:
reduced order model; incompressible Navier-Stokes equations; finite difference approximation; coupling method
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
On the development of a numerical model for the simulation of air flow in the human airways
This contribution reports on an ongoing study focusing on reduced order models for incompressible viscous fluid flow in two dimensional channels. A finite difference solver was developed using a ...
Simulating particle-laden flows: from immersed boundaries towards model order reduction
Isoz, Martin; Kubíčková, Lucie; Kotouč Šourek, M.; Studeník, Ondřej; Kovárnová, A.
2023 - anglický
Particle-laden flow is prevalent both in nature and in industry. Its appearance ranges from the trans-port of riverbed sediments towards the magma flow, from the deposition of catalytic material inside particulate matter filters in automotive exhaust gas aftertreatment towards the slurry transport in dredging operations. In this contribution, we focus on the particle-resolved direct numerical simulation (PR-DNS) of the particle-laden flow. Such a simulation combines the standard Eulerian approach to computational fluid dynamics (CFD) with inclusion of particles via a variant of the immersed boundary method (IBM) and tracking of the particles movement using a discrete element method (DEM). Provided the used DEM allows for collisions of arbitrarily shaped particles, PR-DNS is based (almost) entirely on first principles, and as such it is a truly high-fidelity model. The downside of PR-DNS is its immense computational cost. In this work, we focus on three possibilities of alleviating the computational cost of PR-DNS: (i) replacing PR-DNS by PR-LES or PR-RANS, while the latter requires combining IBM with wall functions, (ii) improving efficiency of DEM contact solution via adaptively refined virtual mesh, and (iii) developing a method of model order reduction specifically tailored to PR-DNS of particle-laden flows.
Klíčová slova:
particle-laden flow; CFD-DEM; arbitrarily-shaped particles; finite volume method
Dokument je dostupný na externích webových stránkách.
Simulating particle-laden flows: from immersed boundaries towards model order reduction
Particle-laden flow is prevalent both in nature and in industry. Its appearance ranges from the trans-port of riverbed sediments towards the magma flow, from the deposition of catalytic material ...
On Reynolds-averaged turbulence modeling with immersed boundary method
Kubíčková, Lucie; Isoz, Martin
2023 - anglický
The immersed boundary (IB) method is an approach in the computational fluid dynamics in which complex geometry conforming meshes are replaced by simple ones and the true simulated geometry is projected onto the simple mesh by a scalar field and adjustment of governing equations. Such an approach is particularly advantageous in topology optimizations (TO) where it allows for substantial speed-up since a single mesh can be used for all the tested topologies. In our previous work, we linked our custom IB variant, the hybrid fictitious domain-immersed boundary method (HFDIB), with a TO framework and successfully carried out an optimization under laminar flow conditions. However, to allow for optimizations of reallife components, the IB approach needs to be coupled with an affordable turbulence modeling. In this contribution, we focus on extending the HFDIB approach by the possibility to perform Reynolds-averaged simulations (RAS). In particular, we implemented the k − ω turbulence model and wall functions for closure variables and velocity.
Klíčová slova:
immersed boundary; RAS; wall functions; CFD; OpenFOAM
Dokument je dostupný na externích webových stránkách.
On Reynolds-averaged turbulence modeling with immersed boundary method
The immersed boundary (IB) method is an approach in the computational fluid dynamics in which complex geometry conforming meshes are replaced by simple ones and the true simulated geometry is ...
Finite element modal analysis of a silicone vocal fold filled with fluid
Hájek, P.; Radolf, Vojtěch; Horáček, Jaromír; Švec, J. G.
2023 - anglický
A three dimensional (3D) finite element (FE) model of a silicone vocal fold (VF) filled with fluid is presented here. The silicone part of the model is based on partial differential equations of the continuum mechanics and consider large deformations. The fluid domain encapsulated in the silicone VF is defined semianalytically as a lumped-element model describing the fluid in hydrostatic conditions. The elongated and pressurized silicone VF was subjected to perturbed modal analysis. Results showed that the choice of the fluid inside the VF substantially influences the natural frequencies. Namely, the water-filling lowers the natural frequencies approximately by half over the air-filling. Besides, the procedure of reverse engineering for obtaining the geometry of the VF from already 3D-printed mold is introduced.
Klíčová slova:
perturbed modal analysis; finite element method; vocal folds; reverse engineering; biomechanics of voice
Dokument je dostupný na externích webových stránkách.
Finite element modal analysis of a silicone vocal fold filled with fluid
A three dimensional (3D) finite element (FE) model of a silicone vocal fold (VF) filled with fluid is presented here. The silicone part of the model is based on partial differential equations of the ...
Proměny interpretace hudebního folkloru: od ochrany každodenní kultury po vznik hudebního žánru (na příkladu České republiky)
Uhlíková, Lucie; Pavlicová, M.
2023 - český
Od 60. let 20. století se v české etnologii začaly rozvíjet snahy, které postupně začaly zařazovat projevy folkloru v jejich druhé existenci do odborného výzkumu. Oblast folklorismu se někdy překrývala s existujícími lidovými tradicemi, někdy na ně navazovala a někdy se jimi pouze v různé míře inspirovala. Rozlišení v takto vymezených kategoriích nebylo snadné ani v minulosti a s příchodem stále rychlejším vývojem společnosti se v obecném povědomí rozostřilo. V tomto rámci vznikl současný široký hudební žánr zakořeněný v hudebním folkloru, který není snadné obsahově vymezit. Příspěvek nastiňuje průběh jeho historického formování, ukazuje modelové momenty jeho vývoje a zabývá se jeho polyfunkčností: mnoho kolektivů se prezentuje nejen na jevišti (spolu s tanečníky) a v hudebních pořadech. koncertním prostředí (samostatně), podílí se ale také na místních etnokulturních tradicích, tanečních zábavách, rodinných oslavách (svatby, narozeniny) a komerčně zaměřených akcích. akce. K ilustraci popsaných faktů článek využívá archivní pramenný materiál a terénní výzkum založený na základě rozhovorů s vybranými hudebníky From the 1960s onwards, efforts began to develop in Czech ethnology, which gradually began to include folklore manifestations in their second existence in professional research. The field of folklorism sometimes overlapped with the existence of folk traditions, sometimes built on them, and sometimes was only inspired by them to varying degrees. The distinction in such defined categories was not easy even in the past, and with the increasingly rapid development of society, it became blurred in the general consciousness. Within this scope, a contemporary broad music genre, music folklore, has emerged that is not easy to define in terms of content. In this paper, the authors outline its historical formation, show model moments of its development, and deal with its polyfunctionality: many collectives present themselves not only on stage (together with dancers) and in concert settings (independently), but also participate in local ethno-cultural traditions, dance parties, family celebrations (weddings, birthdays), and commercially focused events. To illustrate this, the paper uses archival source material, and field research based on interviews with selected musicians.
Klíčová slova:
Music folklore; transformations of folk tradition; music genre; folk revivalism in the Czech Republic
Dokument je dostupný na externích webových stránkách.
Proměny interpretace hudebního folkloru: od ochrany každodenní kultury po vznik hudebního žánru (na příkladu České republiky)
Od 60. let 20. století se v české etnologii začaly rozvíjet snahy, které postupně začaly zařazovat projevy folkloru v jejich druhé existenci do odborného výzkumu. Oblast folklorismu se někdy ...
From John Graunt to Adolphe Quetelet: on the Origins Of Demography
Kalina, Jan
2023 - anglický
John Graunt (1620-1674) and Adolphe Quetelet (1796-1874) were two important personalities, who contributed to the origins of demography. As they both developed statistical techniques for the analysis of demographic data, they are important also from the point of view of history of statistics. The contributions of both Graunt and Quetelet especially to the development of mortality tables and models are recalled in this paper. Already from the 17th century, the available mortality tables were exploited for computing life annuities. Also the contribution of selected personalities inspired by Graunt are recalled here, the work of Christian Huygens, Jacob Bernoulli, or Abraham de Moivre is discussed to document that the historical development of statistics and probability theory was connected with the development of demography.
Klíčová slova:
history of demography; history of statistics; probability theory; moral statistics; mortality tables
Dokument je dostupný na externích webových stránkách.
From John Graunt to Adolphe Quetelet: on the Origins Of Demography
John Graunt (1620-1674) and Adolphe Quetelet (1796-1874) were two important personalities, who contributed to the origins of demography. As they both developed statistical techniques for the analysis ...
MAD UFOs: Magnetically Arrested Discs with persistent Ultra-Fast Outflows
Suková, Petra; Zajaček, M.; Karas, Vladimír
2023 - anglický
We study an outflow that develops in the MAD state in 3D GRMHD simulations. We show that the outflow can be accelerated to\nrelativistic velocities and persist over the course of our simulation. We compare the properties of the outflow from MAD discs with those launched by orbiting secondary at close orbit. The main difference is that the orbiting body launches a more coherent, quasiperiodic ultrafast outflow at lower velocities (v < 0.5c) while the outflow launched in the MAD state (without the body) has a stochastic behaviour and has anapproximately flat velocity distribution between lower anf higher outflow velocities, 0.2c < v < 0.3c and v > 0.5c.
Klíčová slova:
accretion discs; black holes; active galactic nuclei
Dokument je dostupný na externích webových stránkách.
MAD UFOs: Magnetically Arrested Discs with persistent Ultra-Fast Outflows
We study an outflow that develops in the MAD state in 3D GRMHD simulations. We show that the outflow can be accelerated to\nrelativistic velocities and persist over the course of our simulation. We ...
Infants' learning of novel segments is modulated by prosody
Chládková, Kateřina; Podlipský, V.J.; Nudga, Natalia; Paillereau, Nikola; Kynčlová, Kateřina; Šimáčková, Š.
2023 - anglický
Young infants recognize atypical realisations of native-language speech. Later they learn words better from native-accented talkers. However, 6-month-olds preferentially listen to unfamiliar speech. We tested whether the learning of new vowels matches 6-month-olds’ listening preferences, being more effective from nonnative-accented speech. We exposed Czech six-month-olds to delexicalised utterances with consonants replaced by [f] and vowels by 405 tokens sampled from a bimodal [ɛ]-[æ] distribution, a contrast absent from Czech, and with either native or atypical rhythm. Discrimination of [ɛ]-[æ] was then tested in an alternating/non-alternating paradigm. Longer first-look duration to non-alternating than to alternating trials – indicating a learning effect – was found in infants familiarised with the novel contrast in atypical rhythm, such effect was not\ndetected after familiarisation with native rhythm. Six-month-olds thus more effectively exploit distributional information about novel vowels from non-native rhythm, which matches their previously reported preferences for listening to novel over familiar accents.
Klíčová slova:
distributional learning; selective learning; non-native rhythm; vowels; infancy
Plné texty jsou dostupné na vyžádání prostřednictvím repozitáře Akademie věd.
Infants' learning of novel segments is modulated by prosody
Young infants recognize atypical realisations of native-language speech. Later they learn words better from native-accented talkers. However, 6-month-olds preferentially listen to unfamiliar speech. ...
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