Počet nalezených dokumentů: 2685
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Exploring Bubble Dynamics with VOF Method Simulations: Insights from Two Fundamental Gas-Liquid Flow Case Studies
Harrandt, Václav
2024 - anglický
The present study focuses on the flow of Taylor bubbles, representing the interaction between the channel wall and the gas phase, and the collision of\na bubble with a vortex ring, serving as a model liquid-gas interaction. Understanding the former case can be essential to prevent the membrane\nfouling or the flow induced corrosion. The dynamics of the latter case is the predictive criterion for whether the initial mother bubble will break up into the daughter bubbles or not2 and this process can therefore be used as an idealized model of turbulent bubble flow. Klíčová slova: bubble dynamics; multiphase interaction,; numerical simulation Plné texty jsou dostupné v digitálním repozitáři NUŠL
Exploring Bubble Dynamics with VOF Method Simulations: Insights from Two Fundamental Gas-Liquid Flow Case Studies

The present study focuses on the flow of Taylor bubbles, representing the interaction between the channel wall and the gas phase, and the collision of\na bubble with a vortex ring, serving as a model ...

Harrandt, Václav
Ústav chemických procesů, 2024

The Influence of Geometric Parameters of 3D Printed Structured Beds on Hydrodynamic Characteristics of Trickle-Bed Reactor
Nyklíčková, Kateřina
2024 - anglický
The study examines a parametric set of POCS structures, where cubic cell is the basic element. The parameters such as strut diameter sd and cell size cs were varied1. These modifications are implemented with an emphasis on maintaining similar porosity and specific surface area for these structures. Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
The Influence of Geometric Parameters of 3D Printed Structured Beds on Hydrodynamic Characteristics of Trickle-Bed Reactor

The study examines a parametric set of POCS structures, where cubic cell is the basic element. The parameters such as strut diameter sd and cell size cs were varied1. These modifications are ...

Nyklíčková, Kateřina
Ústav chemických procesů, 2024

Finite element approximation of fluid structure interaction using Taylor-Hood and Scott-Vogelius elements
Vacek, Karel; Sváček, P.
2024 - anglický
This paper addresses the problem of fluid flow interacting a vibrating solid cylinder described by one degree of freedom system and with fixed airfoil. The problem is described by the incompressible Navier-Stokes equations written in the arbitrary Eulerian-Lagrangian (ALE) formulation. The ALE mapping is constructed with the use of a pseudo-elastic approach. The flow problem is numerically approximated by the finite element method (FEM). For discretization of the fluid flow, the results obtained by both the Taylor-Hood (TH) element and the Scott-Vogelius (SV) finite element are compared. The TH element satisfies the Babuška-Brezzi inf-sup condition, which guarantees the stability of the scheme. In the case of the SV element the mesh, that is created as a barycentric refinement of regular triangulation, is used to satisfy the Babuška-Brezzi condition. The numerical results for two benchmark problems are shown. Klíčová slova: finite element method; arbitrary Lagrangian-Eulerian method; Scott-Vogelius element; Taylor-Hood element Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Finite element approximation of fluid structure interaction using Taylor-Hood and Scott-Vogelius elements

This paper addresses the problem of fluid flow interacting a vibrating solid cylinder described by one degree of freedom system and with fixed airfoil. The problem is described by the incompressible ...

Vacek, Karel; Sváček, P.
Matematický ústav, 2024

Emerging Contaminants in Sewage Sludge: Analysis and Their Removal by Pyrolysis
Hušek, Matěj
2024 - anglický
The study continues with flame retardants (e.g., phosphorus-based or brominated) present in sludge, which may pose a hazard to nature and human health3,4. There is a lack of information on their pyrolysis removal and occurrence in the sludge in the Czech Republic. Klíčová slova: sewage sludge; pyrolysis; PFAS; flame retardants Plné texty jsou dostupné v digitálním repozitáři NUŠL
Emerging Contaminants in Sewage Sludge: Analysis and Their Removal by Pyrolysis

The study continues with flame retardants (e.g., phosphorus-based or brominated) present in sludge, which may pose a hazard to nature and human health3,4. There is a lack of information on their ...

Hušek, Matěj
Ústav chemických procesů, 2024

Cholinium Based Ionic Liquids: Influence of Water as a Co-solvent on Their Physico-chemical Properties and Preliminary Results for Dissolution of Biopolymers
Souvenir Zafindrajaona, Mahasoa-Salina
2024 - anglický
Ionic liquids (ILs) are emerging as promising alternative solvents in the field of natural substance extraction, offering significant advantages over traditional solvents. Since the last decade, we notice the increasing use of greener solvent alternatives such as Natural Deep Eutectic Solvents (NaDES) or ILs for the extraction of highly valuable compounds from natural sources such as lignocellulose. During this presentation, the influence of water on heat capacity, density, speed of sound and TGA will be discussed and the preliminary results for lignin dissolution willbe presented. Plné texty jsou dostupné v digitálním repozitáři NUŠL
Cholinium Based Ionic Liquids: Influence of Water as a Co-solvent on Their Physico-chemical Properties and Preliminary Results for Dissolution of Biopolymers

Ionic liquids (ILs) are emerging as promising alternative solvents in the field of natural substance extraction, offering significant advantages over traditional solvents. Since the last decade, we ...

Souvenir Zafindrajaona, Mahasoa-Salina
Ústav chemických procesů, 2024

Galloping of insulated bundled overhead line - nonlinear numerical analysis in time domain
Macháček, Michael; Hračov, Stanislav
2024 - anglický
Our contribution focuses on a 3D numerical nonlinear analysis of galloping in a specific bundled overhead line with ice accretion. We studied the susceptibility to this self-excited oscillation, critical onset wind speeds, and global dynamic response of a very low-tensioned line with simulated icing observed on similar real conductors. Due to the highly nonlinear mechanical behavior of such a flexible cable, we employed the Newmark integration method combined with the iterative Newton-Raphson method. We analyzed two numerical models of the overhead line loaded by the wind: one assuming nonlinearity only in the wind load, while retaining the linearity of the mechanical system itself, and the other representing a fully nonlinear system including geometrical nonlinearity. Our analysis revealed that the determined critical wind speeds for the onset of galloping are in relatively close ranges for both models. However, numerical simulations with the fully nonlinear system indicated significantly lower amplitudes of limit cycle oscillations, especially at higher wind speeds, compared to the linear model of the line. This underscores the necessity of using fully nonlinear models during the design stage of such low-tensioned aerial conductors. Klíčová slova: aerial bundled conductors; wind effects; galloping; limit cycle oscillation Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Galloping of insulated bundled overhead line - nonlinear numerical analysis in time domain

Our contribution focuses on a 3D numerical nonlinear analysis of galloping in a specific bundled overhead line with ice accretion. We studied the susceptibility to this self-excited oscillation, ...

Macháček, Michael; Hračov, Stanislav
Ústav teoretické a aplikované mechaniky, 2024

Flow simulations approach for flocculation tanks
Idžakovičová, Kristýna; Bílek, Vojtěch; Haidl, Jan; Isoz, M.; Pivokonský, Martin
2024 - anglický
Flocculation in water treatment facilities plays a key role in the separation of colloidal inorganic and organic substances. Its optimization leads to a significant increase in its efficiency and savings of operational costs. However, it is currently based on trial-and-error experimental approaches. In this contribution, we focus on flow modeling in stirred flocculation tanks that would, after coupling with a calibrated model of particle aggregation, enable simulationbased flocculation optimization. Despite the abundance of literature on stirred tank modeling, there is no universal agreement on the methodology used to describe turbulence nor on the approach to the computational mesh creation. Consequently, there is no unified methodology for simulations and their validation. To address this, we present a best-practice methodology for economical, yet reliable flow simulations in the said device. This methodology includes the choice of the turbulence model, the approach to the design of a high quality mesh suitable for arbitrary geometries, and results evaluation. It is developed based on an extensive literature review, a multitude of flow simulations using several meshes of progressively higher quality and resolution, and various strategies to converge to steady-state flow conditions. The simulation quality indicators used here involve comparison with the experimental data on fluid velocity, stirrer power output, and flow rate through the impeller zone. Additionally, the resulting flow simulation models are compared using tracer transport simulations, hinting at their potential for coupling with particle aggregation models. Klíčová slova: flocculation tank; stirring; MRF; CFD; OpenFOAM Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Flow simulations approach for flocculation tanks

Flocculation in water treatment facilities plays a key role in the separation of colloidal inorganic and organic substances. Its optimization leads to a significant increase in its efficiency and ...

Idžakovičová, Kristýna; Bílek, Vojtěch; Haidl, Jan; Isoz, M.; Pivokonský, Martin
Ústav pro hydrodynamiku, 2024

Growth and Phosphorus Dynamics During Tolypothrix tenuis Cultivation – a Cyanobacterium of Biotechnological Potential
Mušálková, Petra
2024 - anglický
Here I investigated the course of biomass growth, phosphorus uptake and changes in intracellular phosphorus content in T. tenuis in a batch cultivation. Cultivation experiment was held in multiple bubble columns during a light regime (alternating light and dark periods 16 and 8h). Thanks to this experiment I was able to obtain a growth curve of T. tenuis. The decrease of phosphorus concentration in the medium was disproportionally faster\nthan biomass growth resulting in significant oscillations of phosphorus content in the biomass, which are typical characteristics for LPU. It was also observed, that after all phosphorus was removed from the medium, the algae growth continues over time, while obviously utilizing intracellular phosphorus reserves. These findings are valuable in course of using this cyanobacterium for efficient bioremediation of eutrophic water based on phosphorus removal by targeted algae cultivation. Plné texty jsou dostupné v digitálním repozitáři NUŠL
Growth and Phosphorus Dynamics During Tolypothrix tenuis Cultivation – a Cyanobacterium of Biotechnological Potential

Here I investigated the course of biomass growth, phosphorus uptake and changes in intracellular phosphorus content in T. tenuis in a batch cultivation. Cultivation experiment was held in multiple ...

Mušálková, Petra
Ústav chemických procesů, 2024

Influence of Material Properties and Mixing Dynamics on Heat Transport in Granular Materials
Kokavcová, Anna
2024 - anglický
This study evaluates the effect of rotational speed on heat transfer and analyzes particle motion at different stirrer rotational frequencies to understand how primary and secondary flows affect heat transfer efficiency. It also examines the effect of Young’s modulus on heat transfer at different agitator\noperating speeds. Key simulation parameters and their influence 33 on heat transfer efficiency are detailed to improve the reproducibility and applicability of the results. Klíčová slova: granular mixing; heat transfer; DEM Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Influence of Material Properties and Mixing Dynamics on Heat Transport in Granular Materials

This study evaluates the effect of rotational speed on heat transfer and analyzes particle motion at different stirrer rotational frequencies to understand how primary and secondary flows affect heat ...

Kokavcová, Anna
Ústav chemických procesů, 2024

Numerical study of the steady airflow in the human respiratory system during inhaling and exhaling
Lancmanová, Anna; Bodnár, Tomáš
2024 - anglický
This paper presents some of the initial results of the numerical simulations of a steady turbulent flow in human upper airways during inhalation and exhalation. The mathematical model is based on the system of Reynolds-Averaged incompressible Navier-Stokes equations complemented by the SST k − ω turbulence model. The simulations were performed using finite-volume open source solver OpenFOAM on a realistic three-dimensional geometry. The main aim of this particular study is to verify the computational setup with special focus on appropriate choice and implementation of boundary conditions. The prescribed boundary conditions are chosen to mimic the physiological conditions during normal breathing cycle. This study aims to gain an insight into the airflow behavior during the inhalation and exhalation process by comparing the results of two distinct simulations corresponding to two different (opposite) flow rates . The obtained local flow rates and flow fields for both cases are presented and mutually compared. This initial work should serve as a foundation for future more complex simulations that will include the time-dependent and compressible effects. Klíčová slova: human airways; incompressible Navier-Stokes; OpenFOAM Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Numerical study of the steady airflow in the human respiratory system during inhaling and exhaling

This paper presents some of the initial results of the numerical simulations of a steady turbulent flow in human upper airways during inhalation and exhalation. The mathematical model is based on the ...

Lancmanová, Anna; Bodnár, Tomáš
Matematický ústav, 2024

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