Národní úložiště šedé literatury Nalezeno 265 záznamů.  předchozí11 - 20dalšíkonec  přejít na záznam: Hledání trvalo 0.01 vteřin. 
Kvalitativní řešení interakce smykové vrstvy se syntetizovaným proudem.
Falta, Jiří ; Maršík, František (vedoucí práce) ; Popelka, Lukáš (oponent) ; Uruba, Václav (oponent)
This thesis investigates possibilities of suppressing the boundary layer separation which is made by controling boundary layer stability. Orr-Sommerfeld equation is numerically solved for this purpose and its solution was tested on Blasius boundery layer which stability is described in many specialized publications. Transition to turbulence is found out by eN method. Single-variable description of velocity pro les on own surface, which is based on the aproximative properties of Falkner-Skan equation, was used. Process of transition on the aerofoil NACA 63-418 was solved as an example of using proposed computational programs.
Experimental investigations of liquid helium flows
Švančara, Patrik ; La Mantia, Marco (vedoucí práce) ; Mordant, Nicolas (oponent) ; Uruba, Václav (oponent)
Experimentální studium proudění tekutého helia Vybraná turbulentní proudění He II, supratekuté fáze kapalného 4 He, jsou ex- perimentálně studována. Pro přímou detekci klubka kvantovaných vírů, tenkých topologických defektů supratekuté kapaliny, je využita metoda tlumení druhého zvuku, zatímco pro vizualizaci celkového proudění kapaliny metodou sledování trasovacích částic jsou v He II rozptýleny malé částice tuhého vodíku. Stálý tepelný protiproud v kanále se čtvercovým průřezem je zkoumán na základě známých mechanizmů interakce částic s víry. Ukazujeme, že podél výšky kanálu (v blízkosti topení jež proudění vytváří) se rozvine značná nehomogenita hus- toty vírového klubka. V turbulentním proudění He II jsou nalezeny mechanizmy přenosu energie, které se významně liší od mechanizmů přenosu energie v turbu- lentních prouděních viskózních tekutin. Dále pozorujeme jak jednotlivé částice v protiproudu intermitentně střídají dva režimy pohybu podél svých trajektorií; tyto režimy jsou v práci identifikovány a kvalitativně popsány. Navíc je v He II pomocí protiproudu realizován stálý paprsek, v němž je studováno prostorové rozložení vírového klubka. V He II jsou též pozorovány tepelně...
The Effect of Angle of Attack on a Blade Cascade with Overlap
Procházka, Pavel P. ; Uruba, Václav ; Pešek, Luděk
This experimental study was carried out to study an aeroelastic coupling in the case of a blade cascade with overlap exposed to tunnel freestream of different angle of attack (AoA). Three of five blades were constructed to allow vertical position changing by the effect of three shakers. Particle Image Velocimetry was used to measure averaged velocity and dynamical parameters of the flow. Mainly, the effect of AoA will be discussed as well as the influence of blade enlargement and Re number. The influence of potential endplates will be indicated.
On the 3D Dynamics of the Wake Behind a Circular Cylinder
Uruba, Václav ; Procházka, Pavel P. ; Skála, Vladislav
Flow in the wake of a circular cylinder is studied experimentally using time-resolved stereo PIV method. Special attention is paid to 3D topology of dynamical structures. While the distribution of statistic quantities along the cylinder is uniform, and i.e. 2D, the instantaneous flow structure is fully 3D. Within the velocity fluctuating flow field the structures containing streamwise vorticity and velocity components are dominant. The POD modes connected with von Kármán vortex street are identified.
Development of Vibration Equipment for the Production, of Polycomponent Phytomixtures
Yanovych, V. ; Duda, D. ; Rubanenko, O. ; Uruba, Václav
One of the most important stages of the technological process of manufacturing complex pharmaceutical mixtures is the grinding of pre-dried phytosteramines with a gradual sifting and giving it a homogeneous consistency of up to 97-98% with additional pharmaceutical ingredients due to mixing.
Anisotropy of Turbulent Flow around an Airfoil
Uruba, Václav ; Procházka, Pavel P. ; Skála, Vladislav
The flow around an airfoil is analyzed from the point of view turbulence anisotropy assessment. The turbulent flow-field in the vicinity of an airfoil is populated by vortices, in some locations they tend to regularity in orientation, i.e. to anisotropy. However in the wake behind the plate as well as in the core of the boundary layer on the plate suction side the turbulence is close to isotropic state.
The Effect of Blade Overlap on Aeroelastic Coupling
Procházka, Pavel P. ; Uruba, Václav ; Pešek, Luděk ; Bula, Vítězslav
This experimental study was established to clarify an aeroelastic coupling in the case of rotational periodic bodies. The blade grid was placed behind the outlet of the blow-down wind tunnel. Three of five blades were constructed to allow vertical position changing by the effect of three shakers. Particle Image Velocimetry was used to measure mean-phase velocity and dynamical parameters of the flow. The effect\nof blade enlargement will be introduced as well as the difference between forward and backward wave propagation.
Structure of the Wake Behind an Airfoil
Uruba, Václav ; Procházka, Pavel P. ; Skála, Vladislav
The wake behind an inclined plate simulating airfoil is to be studied experimentally. The vortical structures are identified eventually. Theirs topology and dynamical behaviour is to be studied in details using the Proper Orthogonal Decomposition method. The stereo time resolved Particle Image Velocimetry technique is used for the experimental research. The vortex trains with oblique orientation and chequered topology have been detected.
Flow in Branched Channel
Uruba, Václav ; Procházka, Pavel P. ; Skála, Vladislav
Flow in a branched channel is investigated experimentally using the PIV method. The branches are issuing from the main cannel perpendicularly, all channels are of rectangular cross-section. The time-mean flow-fields in the main channel and in the branches are studied in details.
Measurement of Turbulence in LP Part of the 1090 MW Steam Turbine
Antoš, Pavel ; Uruba, Václav ; Jonáš, Pavel ; Procházka, Pavel P. ; Skála, Vladislav ; Hoznedl, M. ; Sedlák, K.
The aim of the paper is to demonstrate a use of the hot-wire anemometry for measurement of turbulent fluctuation in a steam turbine. Measurement technique and used methods are presented in the paper. An experimental research was performed in the last stage of LP (lowpressure) part of the 1090 MW steam turbine in nuclear power-plant turbine. The last moving steel blade has a length of 1220 mm. The experiment was carried out by Institute of Thermomechanics of Czech Academy of Science (IT CAS) in cooperation with Doosan Škoda Power s.r.o. (DSPW), the manufacturer of the turbine.

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