Number of found documents: 2825
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Some experimentally determined properties of a profile in case of self-excited oscillations in subsonic flow
Vlček, Václav; Zolotarev, Igor; Kozánek, Jan; Šidlof, Petr; Štěpán, M.
2017 - English
In the wind tunnel of the Institute of Thermomechanics of the AS CR,v .v. i., experiments were realized with the profile NACA0015 in the presence of the self-excited oscillation. The oscillation of the profile with pitch and plunge degrees of freedom was excited by the subsonic air flow. The plunge support had the same elasticity for all experiments, the pitch support had seven different values of elasticity. Within experiments different types of self-excited vibration (flutter, stall flutter, deep stall flutter) were realized. Range of Mach numbers were M=0.08–0.45, when the chord length is used as the characteristic dimension of the profile. The frequency and amplitude characteristics of the oscillating profile were experimentally determined.\n Keywords: airfoil; aeroelasciticy; dynamic stall; stall flutter; limit cycle oscillations; self -excited vibrations Available at various institutes of the ASCR
Some experimentally determined properties of a profile in case of self-excited oscillations in subsonic flow

In the wind tunnel of the Institute of Thermomechanics of the AS CR,v .v. i., experiments were realized with the profile NACA0015 in the presence of the self-excited oscillation. The oscillation of ...

Vlček, Václav; Zolotarev, Igor; Kozánek, Jan; Šidlof, Petr; Štěpán, M.
Ústav termomechaniky, 2017

Aspects of energy storage systems focusing on flywheel technologies
Zapoměl, Jaroslav; Kozánek, Jan
2017 - English
The energy storage devices are used to reduce variation of the power transmitted in complex technological systems. The individual technologies are based on different physical principles and are applicable in different industrial fields. This paper focuses on aspects of the flywheel storage devices that have a direct impact on their design, technological parametres, and extent of their application. Keywords: energy storage systems; flywheel technology; ultra-low friction bearings Available at various institutes of the ASCR
Aspects of energy storage systems focusing on flywheel technologies

The energy storage devices are used to reduce variation of the power transmitted in complex technological systems. The individual technologies are based on different physical principles and are ...

Zapoměl, Jaroslav; Kozánek, Jan
Ústav termomechaniky, 2017

Impact of Turbulence Generators on Turbulent Characteristics and Structures
Kellnerová, Radka; Jurčáková, Klára; Jaňour, Zbyněk
2017 - English
The turbulent generators are routinely used to produce very turbulent flows. Special type of vertically slenderize spires are applied to enhance turbulent diffusion from the surface upwards in order to increase the boundary layer depth. This paper studies the influence of variable upstream distance of generators on formation of both vortical and non-vortical organized structures within a test section. The 2-component 2-dimensional time-resolved particle image velocimetry measurement of the flow was performed in the wind channel with very rough surface. Intermittent flow dynamics was evaluated by means of higher order moments, vorticity, quadrant and wavelet analysis. The downstream evolution of the flow suggests that equilibrium between roughness- and spires-produced turbulence was reached at the distance of 7 spires height.\n Keywords: turbulence generator; wind channel; vorticity; quadrant analysis Fulltext is available at external website.
Impact of Turbulence Generators on Turbulent Characteristics and Structures

The turbulent generators are routinely used to produce very turbulent flows. Special type of vertically slenderize spires are applied to enhance turbulent diffusion from the surface upwards in order ...

Kellnerová, Radka; Jurčáková, Klára; Jaňour, Zbyněk
Ústav termomechaniky, 2017

Application of non-contact vibration measurements on a 48“ blade under low load condition
Kubín, Z.; Liška, J.; Míšek, T.; Procházka, Pavel
2017 - English
The paper describes in detail a Tip-Timing measurement on a combined cycle power plant with a steam turbine power output of 270MW. Newly developed magnetoresistive and optical sensors were used as well as standard eddy-current sensors to measure blade vibration under low load condition and variable back pressure. New hardware solution for the Tip-Timing measurement will is presented as well as results of measurements of relative amplitudes and excited nodal diameters. Keywords: steam turbine; non-contact vibration measurement; magnetoresistive sensor; optical sensor Available at various institutes of the ASCR
Application of non-contact vibration measurements on a 48“ blade under low load condition

The paper describes in detail a Tip-Timing measurement on a combined cycle power plant with a steam turbine power output of 270MW. Newly developed magnetoresistive and optical sensors were used as ...

Kubín, Z.; Liška, J.; Míšek, T.; Procházka, Pavel
Ústav termomechaniky, 2017

Proposal of hyperelastic proportional damping as dissipated energy model of hard rubbers
Šulc, Petr; Pešek, Luděk; Bula, Vítězslav; Košina, Jan; Cibulka, Jan
2017 - English
The paper deals with a stress analysis of hard rubber under large torsion deformations. This study was motivated by effort to find the dependency the dissipated energy on the deformation energy. Based on the results of an experiment, a function of dissipation energy of hard rubbers for finite strains using the theory hyperelasticity was proposed herein analogically as a proportional damping for elastic theory. Samples of hard rubber of different hardness (EPDM, Silicone) were dynamically tested on the developed torsional test-rig at different frequencies, amplitudes. First the Mooney Rivlin model (MRM) for a shear case of loading was analytically developed and then MRM constants were attained by fitting of the MRM to the experimental torsion-deformation curve. These constants were used to obtain the deformation energy of the MRM models. The coefficients of hyperelastic proportional damping relating a dissipated energy to a strain energy were evaluated for tested rubbers on the basis of experimental results. Keywords: torsion vibration; large deformation; hyperelasticity; dissipated energy; deformation energy Available at various institutes of the ASCR
Proposal of hyperelastic proportional damping as dissipated energy model of hard rubbers

The paper deals with a stress analysis of hard rubber under large torsion deformations. This study was motivated by effort to find the dependency the dissipated energy on the deformation energy. Based ...

Šulc, Petr; Pešek, Luděk; Bula, Vítězslav; Košina, Jan; Cibulka, Jan
Ústav termomechaniky, 2017

Rotary laser vibration laboratory
Maturkanič, Dušan; Procházka, Pavel; Voronova, Evgeniya; Košina, Jan
2017 - English
The rotary laser vibration laboratory started the test operation at the Institute of Thermomachanics AS CR, v.v.i. at the end of 2015. The facility enables the research of high power turbomachines rotary bladed wheels. The paper describes the verification tests which were performed and focused on the equipment parameters at different conditions. Keywords: vibration; turbine; blade; laser; non-contact measurement; sensor; diagnostics Available at various institutes of the ASCR
Rotary laser vibration laboratory

The rotary laser vibration laboratory started the test operation at the Institute of Thermomachanics AS CR, v.v.i. at the end of 2015. The facility enables the research of high power turbomachines ...

Maturkanič, Dušan; Procházka, Pavel; Voronova, Evgeniya; Košina, Jan
Ústav termomechaniky, 2017

Incompressible and compressible viscous flow with low Mach numbers
Balázsová, M.; Feistauer, M.; Sváček, Petr; Horáček, Jaromír
2017 - English
In this paper we compare incompressible flow and low Mach number compressible viscous flow. Incompressible Navier-Stokes equations were treated with the aid of discontinuous Galerkin method in space and backward difference method in time. We present numerical results for a flow in a channel which represents a simplified model of the human vocal tract. Presented numerical results give a good correspondence between the incompressible flow and the compressible flow with low Mach numbers. Keywords: compressible Navier-Stokes equations; incompressible Navier-Stokes equations; discontinuous Galerkin method; finite element method; low Mach number flow Available at various institutes of the ASCR
Incompressible and compressible viscous flow with low Mach numbers

In this paper we compare incompressible flow and low Mach number compressible viscous flow. Incompressible Navier-Stokes equations were treated with the aid of discontinuous Galerkin method in space ...

Balázsová, M.; Feistauer, M.; Sváček, Petr; Horáček, Jaromír
Ústav termomechaniky, 2017

Topical Problems of Fluid Mechanics 2017
Šimurda, David; Bodnár, T.
2017 - English
The aim of the conference is to publish and to discuss the latest results of research in fluid mechanics. Keywords: experimental fluid mechanics; mathematical modelling; atmospheric boundary layer; turbulence; multiphase flow; magnetohydrodynamics Available at various institutes of the ASCR
Topical Problems of Fluid Mechanics 2017

The aim of the conference is to publish and to discuss the latest results of research in fluid mechanics.

Šimurda, David; Bodnár, T.
Ústav termomechaniky, 2017

Numerical Simulation of Laminar-Turbulent Transition in Accelerated Flows
Fürst, J.; Příhoda, Jaromír
2017 - English
The article deals with the evaluation of two RANS based models for simulation of transitional flows including heat transfer. The work is focused on the transition and heat transfer in cases of accelerated flows over a flat plate and through a test turbine cascade. Keywords: turbulence; laminar-turbulent transition; finite volume method Fulltext is available at external website.
Numerical Simulation of Laminar-Turbulent Transition in Accelerated Flows

The article deals with the evaluation of two RANS based models for simulation of transitional flows including heat transfer. The work is focused on the transition and heat transfer in cases of ...

Fürst, J.; Příhoda, Jaromír
Ústav termomechaniky, 2017

Simulation of Transonic Flow Through a Mid-Span Turbine Blade Cascade with the Separation-Induced Transition
Straka, P.; Příhoda, Jaromír; Fenderl, D.
2017 - English
The paper deals with the numerical simulation of the transonic flow through a mid-span turbine blade cascade by means of an in-house code based on the EARSM turbulence model of Hellsten [1] completed by the algebraic transition model of Straka and Příhoda [2]. The simulation using the transition model of Langtry and Menter [3] and Menter et al. [4] implemented in the commercial code ANSYS Fluent was used for the comparison. Simulations were carried out for the transonic regime close to the nominal regime. The flow separation on the suction side of the blade is caused by the interaction of the reflected shock wave with the boundary layer. The attention was focused on the modelling of the transition in the separated flow especially on the modelling of the length of the transition region. Numerical results were compared with experimental results. Keywords: mid-section blade cascade; boundary layer transition; shock wave interaction Fulltext is available at external website.
Simulation of Transonic Flow Through a Mid-Span Turbine Blade Cascade with the Separation-Induced Transition

The paper deals with the numerical simulation of the transonic flow through a mid-span turbine blade cascade by means of an in-house code based on the EARSM turbulence model of Hellsten [1] completed ...

Straka, P.; Příhoda, Jaromír; Fenderl, D.
Ústav termomechaniky, 2017

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