No (14409)
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Numerical study of the steady airflow in the human respiratory system during inhaling and exhaling
Lancmanová, Anna; Bodnár, Tomáš
2024 - English
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.
Keywords:
human airways; incompressible Navier-Stokes; OpenFOAM
Available in digital repository of the ASCR
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 ...
Verification of the dynamic properties of a new model turbine wheel with free blades
Voronova, Evgeniya; Procházka, Pavel; Maturkanič, Dušan; Mekhalfia, Mohammed Lamine; Hodboď, Robert
2024 - English
The paper describes a new experimental model of turbine wheel with free blades. Verification tests were carried out using a Doppler laser vibrometer, with a focus on the equipment parameters under various conditions. The measurements were performed in the Laboratory of Rotational Laser Vibrometry originated at the Institute of Thermomechanics AS CR, v.v.i.
Keywords:
natural frequencies; vibration; blade; laser; turbine
Available at various institutes of the ASCR
Verification of the dynamic properties of a new model turbine wheel with free blades
The paper describes a new experimental model of turbine wheel with free blades. Verification tests were carried out using a Doppler laser vibrometer, with a focus on the equipment parameters under ...
Průzkum spojení kamenných bloků ozdobného „klenutíʺ průhledů cimbuří Prašné brány v Praze
Válek, Jan; Kotková, Kristýna; Kozlovcev, Petr
2024 - Czech
Průzkum napojení kamenných prvků cimbuří Prašné brány v Praze pomocí zemního radaru. Cílem je ověření existence propojovacích prvků ve styčné/ložné spáře mezi kameny „zaklenutí“ průhledů cimbuří a bočními opěrami. Interpretace radargramů ukazuje na kamenické spojky. Malta obsahuje železitou příměs. Survey of the connection of the stone elements of the Powder Tower in Prague using ground penetrating radar. The aim is to verify the existence of connecting elements with the „archingʺ of the battlements and side supports. Interpretation of the radargrams points to a stonemasonry dowels. The mortar contains an iron admixture.
Keywords:
ground penetrating radar; masonry joints; NDT survey
Available at various institutes of the ASCR
Průzkum spojení kamenných bloků ozdobného „klenutíʺ průhledů cimbuří Prašné brány v Praze
Průzkum napojení kamenných prvků cimbuří Prašné brány v Praze pomocí zemního radaru. Cílem je ověření existence propojovacích prvků ve styčné/ložné spáře mezi kameny „zaklenutí“ průhledů cimbuří a ...
Materiálová analýza vzorků malt z archeologického kontextu baziliky sv. Václava ve Staré Boleslavi
Válek, Jan; Kozlovcev, Petr; Svorová Pawełkowicz, Sylwia; Kotková, Kristýna
2024 - Czech
Vzorky malt byly popsány pomoci optické mikroskopie a SEM-EDS. Cílem studie bylo jejich vzájemné porovnání. Všechny tři vzorky mají podobnou strukturu i materiálové složení. Surovinou pro výrobu vápna byl jemnozrnný sedimentární vápenec s vysokým obsahem CaCO3. Vápenná matrice má charakter vzdušného vápna. Kromě vápenného pojiva se vyskytuje též prachovojílové pojivo. To je odděleno od vápenného. Zrna písku jsou obalena vápenným pojivem a v meziprostoru je prachovojílová výplň, což ukazuje na přidání této složky jako příměsi do malty až během použití při stavbě. Použitý písek odpovídá místním poměrům, a to jak eolickým pískům (spraším a sprašovým sedimentům) s dominantním výskytem opracovaných křemenných klastů, tak částečně i sedimentům fluviálního původu (zde se jedná především o litoklasty transportované na větší vzdálenost). The mortar samples were characterized by optical microscopy and SEM-EDS. The aim of the study was to compare them with each other. All three samples have similar structure and material composition. The raw material for the lime was fine-grained sedimentary limestone with high CaCO3 content. The lime matrix has the character of air lime. In addition to the lime binder, there is also a mud-clay binder. This is separate from the lime binder. The sand grains are surrounded by the lime binder and there is a mud-clay filler in the intermediate space, indicating that this component was added as an admixture to the mortar only during use in construction. The sand used corresponds to the local conditions, both to aeolian sands (loess and loess sediments) dominated by worked quartz clasts and, in part, to sediments of fluvial origin (here mainly lithoclasts transported over a greater distance).
Keywords:
historic mortar; microscopy; lime binder; earth binder
Available at various institutes of the ASCR
Materiálová analýza vzorků malt z archeologického kontextu baziliky sv. Václava ve Staré Boleslavi
Vzorky malt byly popsány pomoci optické mikroskopie a SEM-EDS. Cílem studie bylo jejich vzájemné porovnání. Všechny tři vzorky mají podobnou strukturu i materiálové složení. Surovinou pro výrobu vápna ...
Testování susceptibility materiálů lineru kompozitních nádob na chladivové plyny (refrigeranty)
Šperl, Martin; Vála, Ondřej; Bejdl, Jan
2024 - Czech
Výzkumná studie o vlivu atmosféry tlakového chladiva na některé materiálové vlastnosti linerů kompozitních nádob Research study about the influences of pressurized refrigerants atmosphere to some material properties of liners
Keywords:
composite vessel; refrigerant; polymer liner; strength
Available at various institutes of the ASCR
Testování susceptibility materiálů lineru kompozitních nádob na chladivové plyny (refrigeranty)
Výzkumná studie o vlivu atmosféry tlakového chladiva na některé materiálové vlastnosti linerů kompozitních nádob...
Experimentální výzkum mechanických a lomověmechanických vlastností potrubí produktovodu DN 150 Bělčice – Třemošná s označením L186, ocel 11 353
Gajdoš, Lubomír; Šperl, Martin; Šorm, Filip; Bejdl, Jan
2024 - Czech
Experimentální výzkum mechanických a lomově-mechanických vlastností trubních vzorků z produktovodu DN 150. Kromě základních statických zkoušek a zkoušek na určení lomové houževnatosti bylo součástí výzkumu i určení kinetiky růstu únavových trhlin vč. analýzy kritické velikosti trhlin. Experimental research of mechanical and fracture mechanical properties of the pipe specimens taken from oil pipeline DN 150. In addition to basic static tests and fracture toughness tests, the research also included the determination of the kinetic of fatigue crack growth, incl. analysis of critical crack size.
Keywords:
J integral; pipeline; toughness; crack
Available at various institutes of the ASCR
Experimentální výzkum mechanických a lomověmechanických vlastností potrubí produktovodu DN 150 Bělčice – Třemošná s označením L186, ocel 11 353
Experimentální výzkum mechanických a lomově-mechanických vlastností trubních vzorků z produktovodu DN 150. Kromě základních statických zkoušek a zkoušek na určení lomové houževnatosti bylo součástí ...
Numerical evaluation of mass-diffusive compressible fluids flows models
Bodnár, Tomáš; Fraunié, P.
2024 - English
This contribution presents first numerical tests of some recently published alternative models for solution of viscous compressible and nearly incompressible models. All models are solved by high resolution compact finite difference scheme with strong stability preserving RungeKutta time stepping. The two simple but challenging computational test cases are presented, based on the double-periodic shear layer and the Kelvin-Helmholtz instability. The obtained time-dependent flow fields are showing pronounced shear and vorticity layers being resolved by the standard as well as by the new mass-diffusive modified models. The preliminary results show that the new models are viable alternative to the well established classical models.
Keywords:
compressible Navier-Stokes; nearly incompressible flow; mass diffusion; compact finite-difference
Available in digital repository of the ASCR
Numerical evaluation of mass-diffusive compressible fluids flows models
This contribution presents first numerical tests of some recently published alternative models for solution of viscous compressible and nearly incompressible models. All models are solved by high ...
Motion of fluids in the moving domain
Nečasová, Šárka
2024 - English
It is a survay paper where the problem of the existence of weak solutions of compressible barotropic solutions in a moving bounded domain is studied.
Keywords:
compressible fluid; moving domain; weak solutions
Available in digital repository of the ASCR
Motion of fluids in the moving domain
It is a survay paper where the problem of the existence of weak solutions of compressible barotropic solutions in a moving bounded domain is studied.
PROPERTIES OF NANOCRYSTALLINE FE-NI PARTICLES PREPARED BY THERMAL REDUCTION OF OXALATE PRECURSORS
Švábenská, Eva; Roupcová, Pavla; Havlíček, Lubomír; Schneeweiss, Oldřich
2024 - English
Recent technological advancements require development of cost-effective and high-performance magnets \nwhich ideally do not contain rare earth metals or noble metals. The promising candidates are Fe-Ni-based \nalloys, in particular, the Fe50Ni50 L10 phase (tetrataenite), which has a great perspective for producing hard \nmagnetic materials. Our study explores a promising method for preparing nanoparticles of Fe-Ni alloy from an \niron-nickel oxalate precursor. The coprecipitation method was employed to prepare oxalate precursors, \nfollowed by controlled thermal decomposition in a reducing hydrogen atmosphere. The morphology and \nproperties of the resulting particles were analysed using scanning electron microscopy (SEM) coupled with \nenergy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Mössbauer spectroscopy (MS), and \nmagnetic measurements.\nThe SEM analysis revealed that the particles have approximately cube-shaped unit cell morphology with a\nsize in a range of 1 - 2 μm. Upon annealing, the samples contain multiple phases with varying Fe-Ni content.\nMagnetic measurements confirmed the formation of magnetically suitable Fe-Ni phases in the samples after \nannealing. Mössbauer spectroscopy emerged as a highly effective method for characterizing individual phases \nof the Fe-Ni system.
Keywords:
Magnetic materials; thermal decomposition; Mössbauer spectroscopy
Available at various institutes of the ASCR
PROPERTIES OF NANOCRYSTALLINE FE-NI PARTICLES PREPARED BY THERMAL REDUCTION OF OXALATE PRECURSORS
Recent technological advancements require development of cost-effective and high-performance magnets \nwhich ideally do not contain rare earth metals or noble metals. The promising candidates are ...
EFFECT OF OXIDE DISPERSION ON ELECTRIC CONDUCTIVITY OF ROTARY SWAGED POWDER-BASED COPPER COMPOSITES
Kunčická, Lenka; Benč, Marek; Kačor, P.; Marek, M.
2024 - English
Copper is a very popular electro-conductive material, however, the mechanical properties of pure Cu are low. They can be typically improved by (micro)alloying, or via structure modifications introduced by optimized deformation and thermomechanical treatments. Designing a Cu-based composite, possibly strengthened by a dispersion of fine oxides, is another way how to favourably improve the strength properties of Cu. In this study, we performed mechanical alloying of a Cu powder with a powder of Al2O3 oxide, which is known to have strengthening effects on metallic materials. After mixing, we sealed the powder mixture into evacuated tubular Cu containers (i.e. cans). As for the consolidation procedure, we applied direct consolidation of the canned powders via the intensive plastic deformation method of rotary swaging, performed under warm conditions. Subsequently, we subjected the swaged conductors to measurements of electric conductivity and detailed structure observations. The results revealed that the applied swaging ratio was sufficient to fully consolidate the canned powders as the final conductor was unrecognizable from a cast alloy from the viewpoints of visual and structure assessment. In other words, the structure did not exhibit any voids or remnants of unconsolidated powder particles. The observed fine grains with homogeneous dispersion of Al2O3 oxide particles provided improvement of the mechanical properties, as proven by microhardness measurements. Moreover, the electric properties remained favourable.
Keywords:
mechanical-properties; extrusion; Copper; oxide dispersion; electric conductivity; rotary swaging; microstructure
Available at various institutes of the ASCR
EFFECT OF OXIDE DISPERSION ON ELECTRIC CONDUCTIVITY OF ROTARY SWAGED POWDER-BASED COPPER COMPOSITES
Copper is a very popular electro-conductive material, however, the mechanical properties of pure Cu are low. They can be typically improved by (micro)alloying, or via structure modifications ...
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