National Repository of Grey Literature 3 records found  Search took 0.01 seconds. 
Unsteady aerodynamic forces measured on a fluttering profil
Vlček, Václav ; Zolotarev, Igor ; Kozánek, Jan
The evaluations of optical measurements of the flow field near the fluttering profile NACA0015 with two-degrees of freedom are presented. Mach number of the airflow was M = 0.21 and M = 0.45, the boundaries of the flutter occurrence. Aerodynamic forces acting on the profile were evaluated in the drag and lift components which enabled to obtain independently the forces corresponding to the upper and lower surfaces of the profile. Using the mentioned decomposition, the new information about mechanism of flutter properties was obtained. The force effects on the upper and lower surfaces are in opposite phases and they are partially eliminated as a result of the circulation around the profile. The cycle changes of this forces cause the permanent energy contribution from the airflow to the vibrating system.
The calculation of the forces and moments acting on the fluttering profile using interferometric measurements
Vlček, Václav ; Kozánek, Jan ; Zolotarev, Igor
Experimental investigation of the profile NACA0015 fixed as a dynamic system with two degree of freedom vibrating in self-excitation modes were measured in the wind tunnel of the Institute of Thermomechanics AS CR by interoferometric methods. The profile moved in the vertical direction and rotated around the elastic axis in 1/3 of the profile chord. Presented results of the aeroelastic measurement correspond to the flow velocity M = 0.28 and Reynolds number 0.34·106. Time depends of the airflow forces and moments acting on the vibrating profile were obtained newly in this contribution. Applied method of the evaluation is now in the process of its evolvement, therefore presented results should be regards as preliminary conclusions.
Porovnání numerické simulace tlaku na povrchu třepetajícího se profilu s experimentem v aerodynamickém tunelu
Horáček, Jaromír ; Sváček, Petr ; Vlček, Václav ; Feistauer, M.
The paper compares original experimental results with numerical solution of a 2D aeroelastic problem. The incompressible turbulent flow over a freely vibrating airfoil, with two degrees of freedom for rotation and translation with large vibration amplitudes, is described by the Reynolds averaged Navier Stokes (RANS) equations written in Arbitrary Lagrangian-Eulerian (ALE) form. The Spalart-Allmaras turbulence model is used and the flow is solved by the stabilized FEM. The numerical results are compared with the optical measurements of flow field araund a fluttering doublecircular arc (DCA) 18% profile elastcally supported in a subsonic wind tunnel. The interferometry method was used for airflow visualization in different phases of the profile motion. The numerical resulults for the pressure on the profile surface are in good agreement with the measurement.

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