Abstract
The paper reports on hot wire turbulence intensity measurements performed in the entry of a suction-type wind tunnel, used for investigation of flow-induced vibration of airfoils and slender structures. The airfoil is elastically supported with two degrees of freedom (pitch and plunge) in the test section of the wind tunnel with lateral optical access for interferometric measurements, and free to oscillate. The turbulence intensity was measured for velocities up to M = 0.3 i) with the airfoil blocked, ii) with the airfoil self-oscillating. Measurements were performed for a free inlet and further with two different turbulence grids generating increased turbulence intensity levels. For the free inlet and static airfoil, the turbulence intensity lies below 0.4%. The turbulence grids G1 and G2 increase the turbulence level up to 1.8% and 2.6%, respectively. When the airfoil is free to oscillate due to fluid-structure interaction, its motion disturbs the surrounding flow field and increases the measured turbulence intensity levels up to 5%.
Highlights
The aircraft lifting surfaces, helicopter blades, propellers, turbine or compressor blades are slender structures subjected to unsteady aerodynamic forces and moments
The turbulence intensity measurements were performed for a set of inlet flow velocities ranging from Ma = 0.1 to Ma = 0.3
The turbulence intensity levels in the entry of the wind tunnel test section used for investigation of the aeroelastic instability of an airfoil with two degrees of freedom were investigated
Summary
The aircraft lifting surfaces (wings, flaps and ailerions, stabilators, elevons and rudders), helicopter blades, propellers, turbine or compressor blades are slender structures subjected to unsteady aerodynamic forces and moments. As such, they are potentially susceptible to aeroelastic instability such as coupled-mode flutter, stall flutter or dynamic stall. The fundamental properties of a self-oscillating NACA0015 airfoil with two degrees of freedom have been studied in a high-speed suction-type wind tunnel of the Institute of Thermomechanics in Nový Knín [3]. The experimental setup allows dynamic measurement of the flow-induced oscillations and time-resolved measurements of the static pressure at four pressure ports on the surface of the airfoil. The flow fields around the airfoil can be monitored either using time-resolved interferometric measurements [3,4] or Schlieren visualizations [5]
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call