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On Finite Element Approximation of Flow Induced Vibration of Elastic Structure
Valášek, J. ; Sváček, P. ; Horáček, Jaromír
In this paper the fluid-structure interaction problem is studied on a simplified model of the human vocal fold. The problem is mathematically described and the arbitrary Lagrangian-Eulerian method is applied in order to treat the time dependent computational domain. The viscous incompressible fluid flow and linear elasticity models are considered. The fluid flow and the motion of elastic body is approximated with the aid of fininite element method. An attention is paid to the applied stabilization technique. The whole algorithm is implemented in an in-house developed solver. Numerical results are presented and the influence of different inlet boundary conditions is discused.
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New Approaches in Numerical Aeroelasticity Applied in Aerodynamic Optimization of Elastic Wing
Navrátil, Jan ; Slavík, Svatomír (oponent) ; Komárek,, Martin (oponent) ; Hlinka, Jiří (vedoucí práce)
The aeroelasticity is an essential discipline involved in the aircraft design, aiming to predict phenomena occurring due to interaction of aerodynamic, elastic and inertial forces. Those phenomena might often lead to catastrophic consequences, thus it must be proven that they do not occur between the speeds bounding the airplane flight envelope. Current aircraft design leads to increased flexibility of the airframe as a result of modern materials application or aerodynamically efficient slender wings. The airframe flexibility influences the aerodynamic performance and it might significantly impact the aeroelastic effects, which can be more easily excited by rigid body motions than in case of stiffer structures. The potential aeroelastic phenomena can occur in large range of speeds involving transonic regime, where the non-linear flow effects significantly influence the flutter speed. Common aeroelastic analysis tools are mostly based on the linear theories for aerodynamic predictions, thus they fails to predict mentioned non-linear effect. The objective of the thesis is, therefore, to design, implement and test an aeroelastic computational tool employing the aerodynamic prediction solver which is able to predict non-linear flow. In the thesis, the main focus is directed to the static aeroelastic simulations. The methods involved in numerical static aeroelastic simulation are presented in the thesis. The implementation of the computational aeroelastic tool was described and the convergence of the coupled solver was investigated. The tool functionality was validated in the test cases involving different types of the aerodynamic and structural models. The tool was applied also in the aerodynamic shape optimization of an elastic wing. The results and computational cost were compared to the rigid wing optimization. Last chapter presents the author's contribution to the research oriented on the assessment of time synchronization scheme for the CFD-CSM coupled problem. The test case used here is a transonic flow around the Benchmark Super-Critical Wing at flutter condition. Results were compared to the experimental data provided by NASA.
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The effect of the pitch support elasticity on the NACA0015 profile aeroelastic properties
Vlček, Václav ; Zolotarev, Igor ; Kozánek, Jan
The aeroelastic experiments realized in wind tunnel of the Institute of Thermomechanics with Mach numbers M ~ 0.20-0.22 and with the interval of Reynolds numbers Re = (2.4-2.6).105, are presented. These results correspond to the self-excited vibration of the profile NACA0015 with two degrees of freedom allowing the profile rotation in 1/3-chord axis and allowing the vertical displacement of the profile. The dependence of vibration frequency on the wind-flow velocity has been obtained. Comparing with the previous experiments the influence of the pitch support elasticity on the profile aeroelastic properties was determined.
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Aeroelastická analýza konstrukce letounu VUT 081 Kondor
Talanda, Tomáš ; Šplíchal, Jan (oponent) ; Juračka, Jaroslav (vedoucí práce)
Tato diplomová práce se zabývá analýzou třepetání letounu VUT 081 Kondor vyvíjeného na Leteckém ústavu Fakulty strojního inženýrství Vysokého učení technického v Brně. Práce obsahuje podrobný popis letounu a jeho konstrukce, výpočet vlastních frekvencí a tvarů kmitání a vlastní flutterovou analýzu, jejímž výsledkem je stanovení kritické rychlosti třepetání. Dále jsou v práci zmíněna konstrukční opatření vedoucí ke zvýšení flutterové odolnosti a splnění předpisu CS-VLA.
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Dynamická analýza válcových komínů stojících za sebou
Harazim, Petr ; Kanický, Viktor (oponent) ; Salajka, Vlastislav (vedoucí práce)
Diplomová práce se zabývá odezvou ocelové konstrukce komína na zatížení větrem. V souladu s dostupnou výkresovou dokumentací byl sestaven podrobný výpočtový model s využitím metody konečných prvků. Nově realizovaná kolona byla postavena již vedle stávajícího komína, tudíž se dá předpokládat, že se tyto stavby budou navzájem ovlivňovat. V práci je podrobně zpracována problematika aerodynamické a aeroelastické stability staršího ocelového komína s využitím programu ANSYS CFX. Zejména jevy odtrhávání vírů v rezonanci s vlastní frekvencí kmitu konstrukce. Zhodnocení stavby obsahuje posouzení pevnosti a výchylek konstrukce. Výpočty jsou zpracovány v souladu s platnými normativy ČSN EN.
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DYMAMESI 2016 - proceedings
Zolotarev, Igor ; Pešek, Luděk
Proceedings of the Colloquium DYNAMICS OF MACHINES AND MECHANICAL SYSTEMS WITH INTERACTIONS (DYMAMESI), that was held in the Institute of Thermomechanics in Prague, March 1 - 2, 2016 deal with problems structural and multibody dynamics, in coupled interacting systems as aero-elasticity, hydro-elasticity, biomechanics, systems with feedbacks and mechatronics. The published papers was divided into the two parts: Interactions - vibration of dynamic systems coupled with surroundings, mechanical systems with feedbacks, mechatronic active elements, measurement methods and identification in interaction problems, interactions in biomechanics, aero- and hydro-elasticity in rotational engines (bearings, blades, sealings, spaces), analytical and numerical methods in solutions of interactions and Dynamics of Machines - dynamics and vibrations of mechanical systems and solids, non-linear systems - stability, bifurcations, chaos, damping technologies - materials, active elements, methods, identification, vibrodiagnostics, fatigue, computational mechanics and experiments.
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Some atypical flutter characteristics of the NACA0015 profile
Vlček, Václav ; Zolotarev, Igor ; Kozánek, Jan ; Štěpán, M.
The part of the aeroelastic experiments with profile carried out in wind tunnel of the Institute of Thermomechanics, v.v.i. at stream velocity M = 0.15-0.38 in the interval of Reynolds numbers Re = (1.8-5.0)•105 is presented. The results relate to the self-excited vibration of the profile NACA0015, which had two degrees of freedom allowing rotation and transverse displacement of the profile. The elasticity of the two degrees of freedom support has not been, during the experiments, changed. The dependence of Strouhal numbers on the speed of the stream.has been obtained. In one case the excitation of an unstable state occured and during the measurement the jump to a stable state arised. The kinematics of the model during this transition is described.in detail.
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Some NACA0015 profile support variants with self-excited vibration in subsonic fluid flow
Vlček, Václav ; Štěpán, M. ; Zolotarev, Igor ; Kozánek, Jan
One of the important domain of the contemporary aeroelasticity is the self-excited vibration of isolated profiles together with the self-excited vibration of profiles located in blade cascades. The Institute of Thermomechanics of the AS is engaged in group of projects concerning this aeroelastic problem. Results presented here were obtained solving a part of them [1-5].This experiments were realized in the wind tunnel of suction type placed in the laboratory of the Institute in Nový Knín. Profile NACA0015 with two degrees of freedom support was used. Profile was embedded with variable rotational and translational elasticity. The attention of this paper is concentrated on the time records and corresponding spectra of the translational and rotational movement during the self-excited vibration of the profile. Further results related to other parameters of this vibration will be published separately.
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