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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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Dynamics of flow around vibrating wing NACA 0012
Uruba, Václav
Flow around vibrating wing consisting of airfoil profile NACA 0012 has been studied experimentally using time resolved PIV technique. The unsteady velocity field close to the profile trailing edge is highly affected by the wing vibrations. The dynamic of the flow is analyzed using BOD technique of the flow-field for cases with and without vibrations. Comparison shows strong influence of the airfoil vibrations on the flow dynamics.
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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.
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Numerical simulation and experiments with the profile NACA 0012
Chládek, Štěpán ; Zolotarev, Igor ; Uruba, Václav
This paper introduces the new model of the airfoil and describes both aeroelastic experiments and numerical simulation with the profile NACA 0012. The aeroelastic is the science which studies the flow-structure interaction. The flow field can cause change of the position of the solid body and the body due to the change of its position influences the flow field. Mathematical description of the interaction has to involve both the equations of the fluid dynamic and the equations of motion of the solid body. The first results will be presented from the measuring in the dynamic laboratory and from the measuring in the wind tunnel. The main aim of the experimental part of this research is to cause a self-oscillated motion of the airfoil and to measure the transient flow field during this motion. The numerical part should be identical with the experimental dates.
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The self-excited vibration of the NACA0015 profile
Vlček, Václav ; Zolotarev, Igor ; Kozánek, Jan
The two-dimensional flow patterns around the profile NACA0015 vibrating in self-excitation modes were measured in the wind tunnel by optical methods. The Mach numbers for the self-excited vibrations were in the interval 0.2 – 0.45. Results of the interferometric measurement and the profile kinematic movements during the self-oscillations are presented.
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The self-excited vibration of the isolated profile in wide interval of Mach numbers
Vlček, Václav ; Kozánek, Jan ; Zolotarev, Igor
In this paper the experimental results of the self-excited vibration of the isolated NACA0015 profile in subsonic airflow are given. The optical and pneumatical methods were used in the wide range of flow velocities (Mach numbers 0,18 – 0,45). The profile was equipped with semi-conductor pressure sensors situated in the profile surface. From obtained interferograms and pressure signals follow complicated relation among phase differences of rotational and transversal profile movement.
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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 THE ROLE OF BOUNDARY LAYER SEPARATION IN FLUID-FLOW - STRUCTURE INTERACTION
Uruba, Václav
Paper is dealing with dynamical aspects of force interaction between surface and flow. Effect of a boundary layer separation on this interaction is analyzed. As an example, the experimental results on circular cylinder in cross-flow are shown. Substantial dynamical behavior of a boundary layer separation is demonstrated. This dynamics involves not only the well known Kármán vortex street, but the structure is much more complicated. The system of separation bubbles was detected as a rule.
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