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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 - anglický
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.
Klíčová slova:
phonation offset; high-speed videolaryngoscopy
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 - anglický
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.
Klíčová slova:
modal analysis; natural frequencies; modes of vibration
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 - anglický
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.
Klíčová slova:
cooling circuit; heat pump; hydrogen bus; refrigerant
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 - anglický
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.
Klíčová slova:
modal analysis; rubber; railway wheel; damping segment
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
A parallel algorithm for flux-based bounded scalar Re-distribution
Isoz, Martin; Plachá, M.
2022 - anglický
Let us assume a bounded scalar function ? : Q = I × ? ? ?0, 1?, I ? R, ? ? R3, where Q is an open bounded domain and its discrete counterpart ?h defined on a computational mesh Qh = Ih × ?h. The problem of redistribution of ?h over ?h ensuring the scalar boundedness while maintaining the invariance of R ?h ?h dV is surprisingly frequent within the field of computational fluid dynamics (CFD). The present contribution is motivated by the case arising from coupling Lagrangian particle tracking and particle deposition within ? h with Eulerian CFD computation. We propose an algorithm for ?h redistribution that is (i) based on fluxes over the computational cells faces, i.e. suitable for finite volume (FV) computations, (ii) localized, meaning that a cell ?h P with ?hP > 1 affects only its closest neighbors with ?h < 1, and (iii) designed for parallel computations leveraging the standard domain decomposition methods.
Klíčová slova:
CFD; OpenFOAM; scalar redistribution
Dokument je dostupný na externích webových stránkách.
A parallel algorithm for flux-based bounded scalar Re-distribution
Let us assume a bounded scalar function ? : Q = I × ? ? ?0, 1?, I ? R, ? ? R3, where Q is an open bounded domain and its discrete counterpart ?h defined on a computational mesh Qh = Ih × ?h. The ...
Octree-generated virtual mesh for improved contact resolution in CFD-Dem coupling
Studeník, O.; Kotouč Šourek, M.; Isoz, Martin
2022 - anglický
The present work is focused on improving the efficiency of a computational fluid dynamics (CFD) – discrete element method (DEM) solver allowing for computations with non-spherical solids. In general, the combination of CFD and DEM allows for simulations of freely moving solid particles within a computational domain containing fluid. The standard approach of CFD-DEM solvers is to approximate solid bodies by spheres, the geometry of which can be fully defined via its radius and center position. Consequently, the standard DEM contact models are based on an overlap depth between particles, which can be easily evaluated for a sphere-sphere contact. However, for a contact between two non-spherical particles, the overlap depth cannot be used and has to be replaced by the more general overlap volume. The precision of the overlap volume computation is (i) crucial for the correct evaluation of contact forces, and (ii) directly dependent on the computational mesh resolution. Still, the contact volume evaluation in DEM for arbitrarily shaped bodies is usually by at least one order of magnitude more demanding on the mesh resolution than the CFD. In order to improve the computational efficiency of our CFD-DEM solver, we introduce the concept of an OCTREEbased virtual mesh, in which the DEM spatial discretization is adaptively refined while the CFD mesh remains unchanged.
Klíčová slova:
HFDIB-DEM; CFD; DEM; washcoating; OpenFOAM
Dokument je dostupný na externích webových stránkách.
Octree-generated virtual mesh for improved contact resolution in CFD-Dem coupling
The present work is focused on improving the efficiency of a computational fluid dynamics (CFD) – discrete element method (DEM) solver allowing for computations with non-spherical solids. In general, ...
The Design and Aerodynamic Testing of DPIK Probe
Procházka, Pavel P.; Barraclough, V.; Skála, Vladislav; Uruba, Václav
2022 - anglický
The isokinetic probe used to detect the liquid phase drift from the cooling tower is presented here. The main motivation is costs reduction that arises during standard drift measurements. The probe was developed in the framework of the grant project between private company 4Jtech and Institute of Thermomechanics. The aerodynamic design and optimization of this probe should fulfill one important criterion – to capture the droplets from the drift with maximal efficiency. Kalorimetric principle is then used to evaluate the amount of trapped water. Standard PIV (Particle Image Velocimetry) measurement technique and modified IPI (Interferometric Particle Imaging) methods were used to measure the flow field topology and the particle size distribution, respectively.
Klíčová slova:
isokinetic probe; cooling tower; PIV; droplet size
Dokument je dostupný na externích webových stránkách.
The Design and Aerodynamic Testing of DPIK Probe
The isokinetic probe used to detect the liquid phase drift from the cooling tower is presented here. The main motivation is costs reduction that arises during standard drift measurements. The probe ...
Investigation of Transonic Flow through Linear Cascade with Single Blade Incidence Angle Offset
Fürst, J.; Musil, Josef; Šimurda, David
2022 - anglický
The contribution deals with numerical and experimental investigation of the effect of incidence angle offset in a two-dimensional section of a flat linear blade cascade in a high-speed wind tunnel. The aim of the work is to complement ongoing research of quasi-stationary approximation of aerodynamic flutter by examination of setups leading to transonic flow regimes. The numerical simulations were realized by finite-volume, in-house code developed on top of the open-source software package OpenFOAM. The experiments were conducted in correspondence with the setting of numerical simulations. The comparison of experimental and numerical data is presented on the isentropic Mach number distributions at various locations in the blade cascade. The description of transonic flow structures in the vicinity of blades is also provided.
Klíčová slova:
compressor cascade; flutter; CFD; finite volumes; experimental validation; transonic
Dokument je dostupný na externích webových stránkách.
Investigation of Transonic Flow through Linear Cascade with Single Blade Incidence Angle Offset
The contribution deals with numerical and experimental investigation of the effect of incidence angle offset in a two-dimensional section of a flat linear blade cascade in a high-speed wind tunnel. ...
Measurement on Compressor Cascade KOBRA
Luxa, Martin; Šimurda, David
2022 - anglický
The report contains results and evaluation of conducted optical (shadowgraph and schlieren technique) and pneumatic measurements on the profile cascade intended for the tip section of the first rotor row compressor blade.
Klíčová slova:
compressor cascade; transonic flow; optical measurement; pneumatic measurement
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Measurement on Compressor Cascade KOBRA
The report contains results and evaluation of conducted optical (shadowgraph and schlieren technique) and pneumatic measurements on the profile cascade intended for the tip section of the first rotor ...
Two-way fluid structure interaction study of aero-engine compressor blade vibration under air excitation
Mekhalfia, Mohammed Lamine; Procházka, Pavel; Tchawou Tchuisseu, Eder Batista; Maturkanič, Dušan; Hodboď, Robert
2022 - anglický
In this paper, we provide a numerical method via FEM software (ANSYS) using two-way Fluid-Structure Interaction (FSI) solver to estimate the blade’s vibration where the force used to excitation is a continuous air jet. This will help to provide data to diagnostic blade condition and health monitoring and a bridge toward a precise study of the blade’s dynamic under rotation and the estimation of blade’s displacement to define the amplitude and the frequency that occurs under different types of excitation which is a pillar for the process of machine condition and health monitoring.
Klíčová slova:
two-way fluid structure interaction (FSI); air excitation; blade tip displacement
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Two-way fluid structure interaction study of aero-engine compressor blade vibration under air excitation
In this paper, we provide a numerical method via FEM software (ANSYS) using two-way Fluid-Structure Interaction (FSI) solver to estimate the blade’s vibration where the force used to excitation is a ...
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