Number of found documents: 2861
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Recent advances in characterisation of subsonic axisymmetric nozzles
Tesař, Václav
2017 - English
Nozzles are devices generating jets. They are widely used in fluidics and also increasingly often in active control of flows past bodies. Being practically always a component of larger system, design and optimisation needs nozzle properties characterisation by an invariant quantity. Perhaps surprisingly, no suitableinvariant has been so far introduced. This article surveys approaches to characterisation quantities and presents several examples of their typical use such as parallel operation of two nozzles, matching a nozzle to its fluid supply source, apparent resistance increase in flows with pulsation, and the secondary invariants of a family of quasi-similar nozzles. Keywords: nozzle; reynolds number; euler number Available at various institutes of the ASCR
Recent advances in characterisation of subsonic axisymmetric nozzles

Nozzles are devices generating jets. They are widely used in fluidics and also increasingly often in active control of flows past bodies. Being practically always a component of larger system, design ...

Tesař, Václav
Ústav termomechaniky, 2017

Wind tunnel for studies of latent heat storage
Tesař, Václav
2017 - English
When a heated solid body temperature reaches the melting point, temperature stops increasing and remains constant until the whole body is completely molten. The heat input during this melting is spent on freeing the body molecules. This latent heat of melting remains inside the body and may be released when the body is cooled and solidifies. This heat was suggested, already several decades ago, for storing thermal energy. The advantage it offers is avoiding high temperature differences - which otherwise decrease effectiveness of storage (by inevitable heat escape by conduction). Also the mass of the body needed to store a given amount of heat is much smaller. For investigations of the melting and solidification processes a special wind tunnel has been designed and is being built in this study. The tested sample of phase change material, encapsulated in a spherical shell, will be exposed in the tunnel to recirculating hot air flow in a 140 mm x 140 mm test section. Sudden decrease in air flow temperature is made by shifting away the whole closed-circuit part of the tunnel and exposing the test section to flow of cold (room temperature) air. Keywords: latent heat; wind tunnel; paraffins Available at various institutes of the ASCR
Wind tunnel for studies of latent heat storage

When a heated solid body temperature reaches the melting point, temperature stops increasing and remains constant until the whole body is completely molten. The heat input during this melting is spent ...

Tesař, Václav
Ústav termomechaniky, 2017

Úvodní rešerše do problematiky porušování heterogenních svarových spojů komponent jaderně energetických zařízení a metodiky opravných svarů typu WOL
Štefan, Jan
2017 - Czech
Tato výzkumná zpráva byla vypracována pro Státní úřad pro jadernou bezpečnost jako dokument pojednávající o návarech typu “weld overlay” (WOL) jakožto technologii a metodice opravy heterogenních svarových spojů komponent jaderně energetických zařízení postihnutých korozním praskáním pod napětím (“stress corrosion cracking”, SCC). Prvním cílem tohoto dokumentu je podat rešerši se základními a obecnými informacemi o uvedené problematice. Druhým cílem je podat kvalifikované doporučení o vhodnosti metodiky WOL na opravu reálných heterogenních svarových spojů v jaderné elektrárně Dukovany. This research report was elaborated for the State Office for Nuclear Safety of the Czech Republic as a document providing information on the cladding of "weld overlay" (WOL) type. WOL is a technology used to repair dissimilar metal welds of various components of nuclear power plants affected by stress corrosion cracking (SCC). The first objective of this report is provision of a research into basics of the problems being discussed. The second objective is the assessment of suitability of WOL cladding as a repair technology for real dissimilar metal welds in Dukovany nuclear power plant. Keywords: stress corrosion cracking; dissimilar metal welds; weld overlay Available at various institutes of the ASCR
Úvodní rešerše do problematiky porušování heterogenních svarových spojů komponent jaderně energetických zařízení a metodiky opravných svarů typu WOL

Tato výzkumná zpráva byla vypracována pro Státní úřad pro jadernou bezpečnost jako dokument pojednávající o návarech typu “weld overlay” (WOL) jakožto technologii a metodice opravy heterogenních ...

Štefan, Jan
Ústav termomechaniky, 2017

Testing of tip-timing method with multipoint optical system for laboratory measurement of bladed wheel vibration
Pešek, Luděk; Půst, Ladislav; Bula, Vítězslav; Cibulka, Jan
2016 - English
The multipoint optical system for the accurate laboratory measurement of blade vibration under rotation was proposed in IT AS CR. This method is based on the fast optical-elements that register time passages of the blades. The description of the method, results of numerical simulations and first experimental results of the model bladed wheel vibration under rotation are herein presented. Keywords: blade; tip timing; multipoint optical system Available at various institutes of the ASCR
Testing of tip-timing method with multipoint optical system for laboratory measurement of bladed wheel vibration

The multipoint optical system for the accurate laboratory measurement of blade vibration under rotation was proposed in IT AS CR. This method is based on the fast optical-elements that register time ...

Pešek, Luděk; Půst, Ladislav; Bula, Vítězslav; Cibulka, Jan
Ústav termomechaniky, 2016

Some results of simulations of flows with internal permeable walls
Louda, Petr
2016 - English
The work deals with the numerical modelling of compressible flow in a domain containing permeable walls in its interior, i.e. submerged in the fluid. The aim is to exclude direct simulation and find a model approximating the flow through a permeable plate driven by the static pressure difference between the sides of the wall. The numerical experiments so far enable to understand better forming of parasitic wave structures in the measuring section of the wind tunnel. The model of permeable wall needs further verification. Keywords: turbine cascade; flow with permeable wall; shock wave interaction Available at various institutes of the ASCR
Some results of simulations of flows with internal permeable walls

The work deals with the numerical modelling of compressible flow in a domain containing permeable walls in its interior, i.e. submerged in the fluid. The aim is to exclude direct simulation and find a ...

Louda, Petr
Ústav termomechaniky, 2016

FE modelling of the influence of the lamina propria properties on the vocal folds vibration and produced sound for specific Czech vowels
Hájek, P.; Švancara, P.; Horáček, Jaromír; Švec, J.G.
2016 - English
The developed two-dimensional finite element model of the flow-induced self-oscillation of the human vocal folds is used for solving fluid-structure-acoustic interaction occurring during phonation. The aim is to nalyze the influence of stiffness of superficial lamina propria on vocal folds vibration considering vocal tracts shaped for the vowels [i:] and [u:]. Keywords: modelling of phonation by FEM; biomechanics of voice; fluid -structure - acoustic interaction Available at various institutes of the ASCR
FE modelling of the influence of the lamina propria properties on the vocal folds vibration and produced sound for specific Czech vowels

The developed two-dimensional finite element model of the flow-induced self-oscillation of the human vocal folds is used for solving fluid-structure-acoustic interaction occurring during phonation. ...

Hájek, P.; Švancara, P.; Horáček, Jaromír; Švec, J.G.
Ústav termomechaniky, 2016

Experimentální vyšetřování transsonické mříže se stabilizačním zařízením TIE-BOSS
Radnic, Tomáš; Šimurda, David; Luxa, Martin; Fürst, J.; Hasnedl, D.; Kellner, J.
2016 - Czech
Článek se zabývá vlivem dvou variant stabilizační opěrky Tie-Boss na aerodynamické charakteristiky lopatkové mříže. Vliv opeřek byl vyhodnocen na základě výsledků numerické simulace a experimentu. Vyhodnocení ukázalo, že jeden typ Tie-Bossu způsobuje menší ztráty kinetické energie ale větší otočení proudu. This paper is concerned with investigation of influence of two variants of Tie-Boss on\naerodynamic characteristics of a blade cascade. Conclusions are drawn based on results of\nexperiments and numerical simulations. The results show that one type of Tie-Boss exhibits\nlower losses of kinetic energy but higher flow turning than the other. Keywords: tie-boss; transonic flow; steam turbine Available at various institutes of the ASCR
Experimentální vyšetřování transsonické mříže se stabilizačním zařízením TIE-BOSS

Článek se zabývá vlivem dvou variant stabilizační opěrky Tie-Boss na aerodynamické charakteristiky lopatkové mříže. Vliv opeřek byl vyhodnocen na základě výsledků numerické simulace a experimentu. ...

Radnic, Tomáš; Šimurda, David; Luxa, Martin; Fürst, J.; Hasnedl, D.; Kellner, J.
Ústav termomechaniky, 2016

On 3D flow-structures behind an inclined plate
Uruba, Václav; Pavlík, D.; Procházka, Pavel P.; Skála, Vladislav; Kopecký, V.
2016 - English
Stereo PIV measurements has been performed behind the inclined plate, angle of attack 5 and\n10 deg. Occurrence and dynamics of streamwise structures behind the plate trailing edge have been studied in details using POD method. The streamwise structures are represented by vortices and low- and highvelocity regions, probably streaks. The obtained results support the hypothesis of an airfoil-flow force interaction by Hoffman and Johnson [1,2]. Keywords: flat plate; vorticity; POD Available at various institutes of the ASCR
On 3D flow-structures behind an inclined plate

Stereo PIV measurements has been performed behind the inclined plate, angle of attack 5 and\n10 deg. Occurrence and dynamics of streamwise structures behind the plate trailing edge have been studied ...

Uruba, Václav; Pavlík, D.; Procházka, Pavel P.; Skála, Vladislav; Kopecký, V.
Ústav termomechaniky, 2016

Reconstruction of 3D PIV data in complicated experimental arrangements
Pavlík, D.; Uruba, Václav; Kopecký, V.
2016 - English
In this paper a three-dimensional reconstruction of flow field behind flat plate representing a wing\nis presented. The reconstruction is always performed for pair of 2D vector maps obtained by 3D PIV with two cameras which record measurement area from different locations. Three-dimensional reconstruction can be obtained in various ways. This paper summarizes two: the reconstruction based on the known correspondences and the reconstruction based on the knowledge of intrinsic and extrinsic parameters of cameras. The methods can be used in the cases when it is impossible to use a calibration pattern or when reconstruction by commercial software fails. Keywords: 3D PIV; calibration target; reconstruction Available at various institutes of the ASCR
Reconstruction of 3D PIV data in complicated experimental arrangements

In this paper a three-dimensional reconstruction of flow field behind flat plate representing a wing\nis presented. The reconstruction is always performed for pair of 2D vector maps obtained by 3D PIV ...

Pavlík, D.; Uruba, Václav; Kopecký, V.
Ústav termomechaniky, 2016

Optical measurements on TR-P-4 cascade
Luxa, Martin; Šimurda, David
2016 - English
Report contains results and analysis of optical measurements (interferometry and schlieren photography) on the on the optimised variant of the hub section of the ultra long rotor blade for the last stage of a large output steam turbine. Internal designation of the cascade is TR-P-4. Keywords: hub section; long turbine blade; transonic flow Available at various institutes of the ASCR
Optical measurements on TR-P-4 cascade

Report contains results and analysis of optical measurements (interferometry and schlieren photography) on the on the optimised variant of the hub section of the ultra long rotor blade for the last ...

Luxa, Martin; Šimurda, David
Ústav termomechaniky, 2016

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