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Flutter at a low velocity
Vlček, Václav ; Kozánek, Jan ; Zolotarev, Igor
Aeroelastic experiments with the profile NACA0015 were realized in the suction type aerodynamic tunnel of the Institute of Thermomechanics, Czech Academy of Sciences, Prague. The profile had two degrees of freedom realized in translation and rotation motion and flow velocity was just up its critical value. The flow field was measured with interferometry method and the results obtained at the velocity M = 0.23 in the flutter regime are presented. The evaluation of interferogramms enabled to determine the components of the drag and lift forces.
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Optická měření proudového pole při obtékání samobuzeně kmitajícího profilu
Vlček, Václav ; Kozánek, Jan ; Zolotarev, Igor
V příspěvku jde o interferometrické vyhodnocení aerodynamického měření proudu vzduchu v okolí profilu NACA0015 v režimu samobuzeného kmitání, realizované v aerodynamickém tunelu Ústavu termomechaniky. Zkušební profil vykonával pohyb odpovídající dynamické soustavě o dvou stupních volnosti ve vertikalním směru a rotoval kolem osy umístěné v 1/3 profilu. Odpovídající Machovo číslo bylo 0.45. Je prezentována kinematika profilu, působící síly a momenty během samobuzeného kmitání.
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Analytical and numerical approach to the airfoil stability computation
Chládek, Štěpán ; Horáček, Jaromír
The fluid structure interaction (FSI) represents an important task in many applications. This paper deals with interaction of airfoil and fluid flow and compares two possible ways of computation of the stability boundaries of the system. The airfoil has two degrees of freedom represented by translation h(t) and rotation a(t). The flow acts on the airfoil with aerodynamic forces depending on the flow velocity. Two methods for calculation of the critical flow velocity, when the airfoil loses aeroleastic stability, are described.
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Aeroelastic experiments with the structural properties variation
Chládek, Štěpán ; Zolotarev, Igor ; Uruba, Václav
The paper measurements on a model of the airfoil NACA0012. Usually there is a limit range of the flow velocity in the wind tunnel. The chosen wind tunnel is usually fixed, the only one possibility is to modify the structural properties of the experimental stand. There are presented two kinds of modifications, one is based on the geometry variation, the other one on the added mass approach. Both of them have been verified experimentally.
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On higher-order space-time discretization of an nonlinear aeroelastic problem with the consideration of large displacements
Sváček, P. ; Horáček, Jaromír
This paper focuses on the mathematical and numerical modelling of interaction of the two-dimensional incompressible fluid flow and a flexibly supported airfoil section wit control section. A simplified problem is considered: The flow is modelled by the system of Navier-Stokes equations and the structure motion is described with the aid of nonlinear ordinary differential equations. The time-dependent computational domain is taken into account by the Arbitrary Lagrangian-Eulerian method. Higher order time discretization is considered within the stabilized finite element method. The application of the described method is shown.
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Forces actingon the fluttering. Profile in the wind tunnel
Vlček, Václav ; Kozánek, Jan ; Zolotarev, Igor
2D experiments with profile NACA0015 supported with two degrees of freedom in aerodynamic tunnel of suction type were realized. One degree of freedom was rotation around the profile axis in 1/3 chord distance behind the profile leading edge, the second one was the vertical translation. The interferometric visualization of the flow field in the vicinity of the profile during its self-excited vibration was realized. Forces acting on the profile and the pressure distribution on the profile surface resulting from the interferometric measurements are presented.
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On approximation of an aeroelastic problem in post-critical regimes
Sváček, P. ; Horáček, Jaromír
This paper focused on the mathematical modelling and the numerical approximation of interactions of a simplified problem of the two-dimensional flow and flexibly supported airfoil section with control section. The flow is modelled with the aid of the incompressible Navier-Stokes equations and for the approximation the stabilized finite element method is used. The structure motion is described with the aid of nonlinear ordinary differential equations. The time-dependent computational domain is taken into account by the Arbitrary Lagrangian-Eulerian method.
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O ÚLOZE ODTRŽENÍ MEZNÍ VRSTVY PŘI SILOVÉ INTERAKCI PROUDÍCÍ TEKUTINY S OBTÉKANÝM POVRCHEM
Uruba, Václav
Silová interakce mezi proudící tekutinou a obtékaným tělesem představuje základní inženýrskou úlohu z oblasti mechaniky tekutin. Znalost sil je rozhodující pro dimenzování mechanické konstrukce obtékaného tělesa. Může také ovlivnit funkci zařízení jako celku. Klasické přístupy k této úloze nabízejí kvazistatické řešení. Je vyhodnocena maximální velikost síly. Pokud chceme řešit interakci poddajného tělesa s prouděním, potom nezbývá než řešit úlohu dynamicky. Vzhledem k tomu, že systém poddajné obtékané těleso - tekutina je silně nelineární, nezbývá, než úlohu řešit jako simulaci v čase.
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Incompressible fiscous flow at viscous velocities in interaction with a vibrating profile NACA 0012
Honzátko, R. ; Horáček, Jaromír ; Kozel, Karel
The work presents numerical solution of the interaction of 2D incompressible viscous flow and a freely vibrating profile NACA 0012 with large amplitudes. The upstream flow velocities are consider in the range 5-40 m/s. The profile has two degrees of freedom. It can rotate around an elastic axis and oscillate in the vertical direction. Its motion is described by two nonlinear ordinary differential equations. Fourth-order Runge-Kutta method is used to solve these equations numerically. The incompressible Navier-Stokes equations represent the mathematical model of the laminar viscous flow. Numerical schemes of the FVM are applied on a structured Quadrilateral C-mesh. The method of artificial compressibility and dual-time stepping method is employed for numerical simulations. Deformations of the computational domain are treated using the ALE method. Numerical simulations of the profile motion are performed for the case solved earlier by the FE method, and the results are in good agreement.
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