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The new HPC results of 3D FE modelling of dry-friction damping at tie-boss couplings of bladed wheel - 6nd resonant mode
Pešek, Luděk; Šnábl, Pavel; Bula, Vítězslav
2021 - English
The paper is a direct continuation of our study published in the last colloquium DYMAMESI. This paper deals with the new results of dry-friction damping calculation of the bladed wheel with tie-boss couplings vibrating at a higher resonant mode, i.e. mode with 6 nodal diameters (ND). The numerical solution of the wheel based on 3D finite element method with surface-to-surface dry friction contact model is applied. Due to dry friction contacts and non-linear solution, it leads to HPC computations and long computation times. Therefore, the earlier proposed computational strategy for damping evaluation where the resonant attenuation is computed directly from the defined resonant initial conditions given by the 6ND mode is used. Comparison of experimental and numerical results of dynamical behaviour of the bladed wheel yields a reasonable agreement for the studied vibration mode.
Keywords:
bladed wheel; dry-friction contacts; damping; tie-boss couplings
Available at various institutes of the ASCR
The new HPC results of 3D FE modelling of dry-friction damping at tie-boss couplings of bladed wheel - 6nd resonant mode
The paper is a direct continuation of our study published in the last colloquium DYMAMESI. This paper deals with the new results of dry-friction damping calculation of the bladed wheel with tie-boss ...
Verification of our deformation member for measuring axial force under torsional dynamic load
Šulc, Petr; Pešek, Luděk; Štěpánek, Ivo; Šnábl, Pavel; Bula, Vítězslav
2021 - English
This paper deals with experimental testing of hard rubbers under torsional harmonic loading on an axial torsional servohydraulic testing machine Instron 8852. In evaluating these experiments, we focused on obtaining axial forces and elongation, which is a confirmation of the so-called Poynting effect under torsional loading. An important result from these experiments is a comparison of axial forces from this device with the results from our designed and assembled torsion device with a deformation member for measuring axial forces, which brings us some verification of this device.
Keywords:
axial force; torsion dynamic load; hard rubber; Poynting effect
Available at various institutes of the ASCR
Verification of our deformation member for measuring axial force under torsional dynamic load
This paper deals with experimental testing of hard rubbers under torsional harmonic loading on an axial torsional servohydraulic testing machine Instron 8852. In evaluating these experiments, we ...
Numerical simulation of dynamic loading of a test blade in forced torsional vibration
Šidlof, P.; Vomáčko, V.; Lepičovský, Jan; Šimurda, David; Štěpán, M.; Luxa, Martin
2021 - English
Within a new project focused on blade flutter research, building on previous experience with the NASA Transonic Flutter Cascade facility, static blade cascade and airfoil flutter experiments realized in cooperation between the Institute of Thermomechanics and Technical University of Liberec, a new test facility is under development for the investigation of high subsonic and transonic flow in a blade cascade under forced torsional oscillation. Apart from aerodynamic loading of the blades, the oscillating blade will be exposed to significant structural stresses due to the highfrequency torsional vibration. In order to avoid structural integrity issues from high-cycle fatigue, a numerical simulation of the stress and displacement of the blade was realized. Regions where equivalent stress reaches maximum values were identified, and elastic deformations were computed. The limits in oscillation amplitude and frequency for the safe operation of the experimental setup were discussed.
Keywords:
blade flutter; structural analysis; torsional vibration
Available at various institutes of the ASCR
Numerical simulation of dynamic loading of a test blade in forced torsional vibration
Within a new project focused on blade flutter research, building on previous experience with the NASA Transonic Flutter Cascade facility, static blade cascade and airfoil flutter experiments realized ...
Comparison of Transonic Flows Through Two Tip-Section Turbine Blade Cascades with Different Flat Profiles
Musil, Josef; Příhoda, Jaromír; Fürst, J.; Luxa, Martin; Šimurda, David
2021 - English
The contribution deals with numerical simulations of 2D compressible flow through two variants of the tip-section turbine blade cascade with a flat profile for the subsonic inlet. Simulations were realised by means of the OpenFOAM code using the γ-Reθ bypass transition model completed by the two-equation SST turbulence model. Predictions were focused particularly on the impact of the shock-wave/boundary-layer interaction on the flow structure in the inter-blade channel. Beside the effect of the inlet angle on the flow around the leading edge was studied. Numerical results were compared with optical and pressure experimental data.
Keywords:
supersonic tip-section blade cascade; CFD; transition modelling
Fulltext is available at external website.
Comparison of Transonic Flows Through Two Tip-Section Turbine Blade Cascades with Different Flat Profiles
The contribution deals with numerical simulations of 2D compressible flow through two variants of the tip-section turbine blade cascade with a flat profile for the subsonic inlet. Simulations were ...
Spectral/hp elements in fluid structure interaction.
Pech, Jan
2021 - English
This work presents simulations of incompressible fluid flow interacting with a moving rigid body. A numerical algorithm for incompressible Navier-Stokes equations in a general coordinate system is applied to two types of body motion, prescribed and flow-induced. Discretization in spatial coordinates is based on the spectral/hp element method. Specific techniques of stabilisation, mesh design and approximation quality estimates are described and compared. Presented data show performance of the solver for various geometries in 2D from slowly moving cylinder to high speed flow around aerodynamic profiles.
Keywords:
spectral/hp element method; fluid structure interaction; spectral vanishing viscosity
Fulltext is available at external website.
Spectral/hp elements in fluid structure interaction.
This work presents simulations of incompressible fluid flow interacting with a moving rigid body. A numerical algorithm for incompressible Navier-Stokes equations in a general coordinate system is ...
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 ...
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 ...
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 tie-bosses 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 ...
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 ...
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 ...
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