Number of found documents: 3044
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On the 3D Dynamics of the Wake Behind a Circular Cylinder
Uruba, Václav; Procházka, Pavel P.; Skála, Vladislav
2020 - English
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. Keywords: circular cylinder; wake; 3D structure; POD Fulltext is available at external website.
On the 3D Dynamics of the Wake Behind a Circular Cylinder

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 ...

Uruba, Václav; Procházka, Pavel P.; Skála, Vladislav
Ústav termomechaniky, 2020

Contribution to hpc fem calculations of bladed disk dynamics with dry-friction contacts
Pešek, Luděk; Šnábl, Pavel; Bula, Vítězslav
2020 - English
The experimental set-up for studying dynamical behaviour of the bladed wheel with pre-stressed dry-friction contacts in tie-bosses was built. The numerical solution of the turbine bladed wheel with tiebosses based on 3D finite element method with surface to surface dry friction contact model is proposed. Comparison of experimental and preliminary numerical results of dynamical behaviour and damping estimation of our bladed wheel design yielded a reasonable agreement. Due to dry friction contacts and non-linear solution of 3D FE model it, however, leads to HPC computations and long computation times. The contribution deals with description of computational strategy for damping evaluation and achieved results, too. Keywords: bladed wheel; dry-friction contacts; damping; tie-boss couplings Available at various institutes of the ASCR
Contribution to hpc fem calculations of bladed disk dynamics with dry-friction contacts

The experimental set-up for studying dynamical behaviour of the bladed wheel with pre-stressed dry-friction contacts in tie-bosses was built. The numerical solution of the turbine bladed wheel with ...

Pešek, Luděk; Šnábl, Pavel; Bula, Vítězslav
Ústav termomechaniky, 2020

Design of experiment for temperature dependence of rubber samples under torsional harmonic load
Šulc, Petr; Pešek, Luděk; Bula, Vítězslav; Košina, Jan; Cibulka, Jan
2020 - English
This work deals with the preparation and methodology of temperature measurement inside the rubber sample. There is a design of a rubber sample with placed temperature sensors and a description with a scheme of temperature measurement under torsional dynamic stress. The reason for these measurements is to determine the temperature dependence and sensitivity of the parameters of the thermal outputs. Keywords: heat flow; temperature; Fourier equation Available at various institutes of the ASCR
Design of experiment for temperature dependence of rubber samples under torsional harmonic load

This work deals with the preparation and methodology of temperature measurement inside the rubber sample. There is a design of a rubber sample with placed temperature sensors and a description with a ...

Šulc, Petr; Pešek, Luděk; Bula, Vítězslav; Košina, Jan; Cibulka, Jan
Ústav termomechaniky, 2020

Comparison of power control method for B4 converter connected to unbalanced grid
Šimek, Petr; Valouch, Viktor
2020 - English
The aim of the paper is to present a power control of a three-phase inverter with only four inverter legs (connections B4) connected to an unbalanced grid. The results obtained by the predictive power control with a finite set of control values, the results obtained using a modified direct power control strategy, and the results obtained using a generalized predictive control are compared and discussed.\n Keywords: power control; B4 converter; unbalanced grid Available at various institutes of the ASCR
Comparison of power control method for B4 converter connected to unbalanced grid

The aim of the paper is to present a power control of a three-phase inverter with only four inverter legs (connections B4) connected to an unbalanced grid. The results obtained by the predictive power ...

Šimek, Petr; Valouch, Viktor
Ústav termomechaniky, 2020

Experimental modelling of vibroacoustics of the human vocal tract with compliant walls
Radolf, Vojtěch; Horáček, Jaromír; Košina, Jan
2020 - English
Experimental model of human vocal tract cavities with hard walls has been modified to take into account the compliance of the soft tissue of the human vocal tract. The paper presents the studied acoustic-structural interaction of the vocal tract cavities with a dynamical system originated in vibration of the soft tissue. The experimental results are in qualitative agreement with the results of mathematical modelling. Compliant walls of acoustic cavities generate additional low frequency acoustical-mechanical resonances of the system and increase acoustic resonance frequencies. Keywords: biomechanics of voice; vocal tract acoustics; acoustic-structural interaction. Available at various institutes of the ASCR
Experimental modelling of vibroacoustics of the human vocal tract with compliant walls

Experimental model of human vocal tract cavities with hard walls has been modified to take into account the compliance of the soft tissue of the human vocal tract. The paper presents the studied ...

Radolf, Vojtěch; Horáček, Jaromír; Košina, Jan
Ústav termomechaniky, 2020

Laminar-Turbulent Transition in View of Flow Separation from Isothermal and Heated Cylinder
Pech, Jan
2020 - English
This work presents insight to the laminar-turbulent transition in flow around cylinder through a numerical simulation, both in isothermal and heated case. The flow is modelled directly as a solution to the Navier-Stokes and Navier-Stokes-Fourier system. Reynolds numbers are considered in range 100-20000, ratio of cylinder-wall and upstream temperature is up to 1.5. Curves representing evolution of separation positions in time provide novel insight to vortex formation. Various regimes are recognized and some of them can be assigned to phenomena described formerly in experiment. Keywords: transition to turbulence; heated flow; cylinder flow; separation angle; Navier-Stokes- Fourier; spectral/hp element method Fulltext is available at external website.
Laminar-Turbulent Transition in View of Flow Separation from Isothermal and Heated Cylinder

This work presents insight to the laminar-turbulent transition in flow around cylinder through a numerical simulation, both in isothermal and heated case. The flow is modelled directly as a solution ...

Pech, Jan
Ústav termomechaniky, 2020

A simple algorithm for probes positioning in BTT systems
Tchawou Tchuisseu, Eder Batista; Procházka, Pavel; Maturkanič, Dušan
2020 - English
The Blade Tip Timing (BTT), a non-contact method for measuring the blade tip displacement through the time of arrival, is studied in this article. This work proposes a simple algorithm based on the minimization of the coherence and the condition number of the sensingmatrix for defining the best probe positioning in the case of synchronous and asynchronous vibrations. Keywords: BTT systems; probe positioning; condition number; coherence Available at various institutes of the ASCR
A simple algorithm for probes positioning in BTT systems

The Blade Tip Timing (BTT), a non-contact method for measuring the blade tip displacement through the time of arrival, is studied in this article. This work proposes a simple algorithm based on the ...

Tchawou Tchuisseu, Eder Batista; Procházka, Pavel; Maturkanič, Dušan
Ústav termomechaniky, 2020

Rázy v potrubí
Luxa, Martin
2020 - Czech
Zpráva se zabývá problematikou rázových vln potrubí, které vznikají při jeho náhlém uzavření. Jsou popsány tři možné teoretické přístupy k řešení a jsou uvedena i řešení praktických úloh. The report deals with shock waves in ducts, which originate as a consequence of sudden closing of quick acting valve. Three methods of solving are described. Selected actual problems of czech power plants are solved. Keywords: water hammer; hydrodynamics; shock wave; aerodynamics Available at various institutes of the ASCR
Rázy v potrubí

Zpráva se zabývá problematikou rázových vln potrubí, které vznikají při jeho náhlém uzavření. Jsou popsány tři možné teoretické přístupy k řešení a jsou uvedena i řešení praktických úloh....

Luxa, Martin
Ústav termomechaniky, 2020

Topical Problems of Fluid Mechanics 2020
Šimurda, David; Bodnár, T.
2020 - English
Proceedings consist of contributions dealing with both research on various problems in fluid mechanics and mathematical or experimental methods utilizable for solution of such problems. Keywords: experimental fluid mechanics; mathematical modelling; CFD; turbulence Available at various institutes of the ASCR
Topical Problems of Fluid Mechanics 2020

Proceedings consist of contributions dealing with both research on various problems in fluid mechanics and mathematical or experimental methods utilizable for solution of such problems.

Šimurda, David; Bodnár, T.
Ústav termomechaniky, 2020

Measurements on TR-W-1 Cascade
Luxa, Martin; Šimurda, David
2020 - English
The research report contains experimetal data from optical and pneumatic measurements on transonic profile cascade with linear part of suction side downstream the sonic line, which is intended for the rotor wheal of a last stage of steam turbine Keywords: transonic flow; steam turbine; profile cascade Available at various institutes of the ASCR
Measurements on TR-W-1 Cascade

The research report contains experimetal data from optical and pneumatic measurements on transonic profile cascade with linear part of suction side downstream the sonic line, which is intended for the ...

Luxa, Martin; Šimurda, David
Ústav termomechaniky, 2020

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