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Flutter methodology using reduced order aeroelastic model
Prasad, Chandra Shekhar ; Pešek, Luděk ; Šnábl, Pavel
The present research project is focused on development of fast and efficient numerical method based on reduced order aeroelastic method (ROAM) for modeling and analysis of \nclassical flutter in the low pressure (LP) stage steam turbine blade. Stability diagram such as aerodynamic damping (AD) of aeroelasticity of cascade of 3D turbine blades used as a prime \ncharacterization factor. In the calculation of the S-curve/AD, the problem of classical flutter formation associated with running waves is considered here. Running waves is simulated by \nthe inter-blade phase shift of the blades in the cascade. Panel method based boundary element flow solver is employed for calculation of unsteady aerodynamic forces. This method is good \ncompromise of speed and accuracy for the estimation of the stability of the blades on a classical flutter. One way loose coupling technique between PM based flow solver and the structural \nmodel. For the structural part modal model synthesis (MMS) method is adopted in the ROAM solver. MMS is adopted to further reduced the computational cost. The ROAM simulated AD \nand pressure distribution over blade is compared high fidelity CFD data on real blade geometry provided by Doosan Skoda Power s.r.o. Furthermore, the ROAM results are also compared \nwith experimentally obtained results on two different linear cascade. The ROAM model shows good agreement with linear cascade results, however, there is noticeable discrepancy with real blade CFD results.
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Identifikace materiálových konstant nových pryží tlumících segmentů z modální analýzy železničního pryží odpruženého kola
Šulc, Petr ; Pešek, Luděk ; Šnábl, Pavel ; Bula, Vítězslav
Cílem modální analýzy bylo porovnat a identifikovat materiálové konstanty dvou navržených směsí pryžových tlumících segmentů železničního kola. Modální analýza byla řešena ve dvou etapách, a to experimentálně a následně numericky. Experimentální modální analýza probíhala v laboratoři ÚT s použitím jednobodového buzení (SIMO) na gumo-odpruženém kole, a to pro obě navržené varianty pryžových segmentů s označením 42809 a 46809. Z této dynamické analýzy byly získány vlastní frekvence a tvary kmitání kola v pásmu do 6,5kHz. Materiálové konstanty pryže byly získány na základě ladění materiálových parametrů pryžových segmentů, tj. modulu pružnosti a koeficientu speciálního modelu proporcionální tlumení, 3D MKP modelu železničního kola na hodnoty vlastních frekvencí a poměrných útlumů vybraných tvarů vlastního kmitání kol.
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Dynamics of Machines and Mechanical Systems with Interactions, DYMAMESI 2021
Zolotarev, Igor ; Pešek, Luděk ; Kozień, M. S.
The aim of the DYMAMESI is to facilitate the exchange of up to date information and knowledge among specialists in structural and multibody dynamics, in coupled interacting systems as aero-elasticity, hydro-elasticity, biomechanics, systems with feedbacks and mechatronics. The colloquium DYMAMESI 2021 is cofunded by the Strategy AV21 initiative of the Czech Academy of Sciences of the Czech Republic, and in 2021 will be hosted by Cracow University of Technology, Institute of Applied Mechanics, Section of Dynamics of Systems.
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Measurement of friction coefficient between damping wire and groove
Šnábl, Pavel ; Pešek, Luděk ; Bula, Vítězslav ; Běhálek, V. ; Boháč, T. ; Tašek, H.
Damping wire is being used on railway wheels for noise suppression. It is inserted into a groove of the wheel and dry friction damping reduces vibrations and thus the noise transmitted by the wheel. For increase of durability of the wire, surface treatment of the groove and the ring must be applied to prevent corrosion. Three combinations of diferent surface treatments were studied during reciprocating motion in a set of measurements with diferent frequencies and normal forces to evaluate friction coeficient. Then, those measurements were repeated after a long-time run to evaluate the change of friction coeficient after the wear of the surfaces.
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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
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.
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Identification of dynamic properties of built electrodynamic shaker
Šnábl, Pavel ; Kozánek, Jan ; Pešek, Luděk
Electrodynamic shaker was built in our institute for excitation of vibrating blade in a flow field. The shaker consists of permanent magnet and voice coil, 3D printed body, core and cover, and two at suspension rings laser-cutted from Pertinax. For simulation purposes of the whole system, identfication of shaker dynamic parameters was needed. Several identification methods in time or frequency domain were used, and it was shown that the shaker model must contain nonlinear stiffness in order to describe the real system more accurately.
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Simple model for investigation of aerodynamic coupling in linear blade cascades
Chládek, Štěpán ; Pešek, Luděk ; Procházka, Pavel P.
Simple viscous-elastic model has been proposed for investigation of aerodynamic coupling in linear blade cascades. One blade is connected with both adjacent blades using idealized springs and dampers which represent viscous fluid. All blades may oscillate with one degree of freedom represented by vertical translation. Energy method using travelling waves model was utilized for aerodynamic damping coefficient derivation. The proposed model does not compute the damping values quantitatively, nevertheless it provides the damping shape analysis. Interesting results are presented within zero and low subsonic flow velocities, where the experiment included velocity flow field measurement.
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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.
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