| Popis: |
This paper presents an experimental analysis of the effect known as “double stall” or “dynamic stall” of an airfoil under incident turbulent flow conditions. In particular, it has been used a Wortmann FX 63-137 airfoil, which is largely used in wind turbine blades. The main objective of the present work is to define the general fluid dynamic configuration around the dynamic stall of the airfoil. At first, a load test was carried out at the LaCLyFA boundary layer wind tunnel in order to aerodynamically characterize the airfoil (through a two axis aerodynamic balance). The characteristic curves of the airfoil for different Reynolds number were obtained from the test, which showed significant parameters such as: Clmax, αstall, etc. After that, a pneumatic system that allows a sudden change in the angle of attack was implemented. Once operable, different flow visualizations tests for different Reynolds numbers and different rates of angle of attack variation were performed. The flow visualization techniques used were: tufts over the airfoil and its wake, a suspension of kerosene and oxide of magnesium and injection of a smoke line in the free stream. According to the visualization results measurements by hot-wire anemometry techniques with 3 simultaneous sensors placed in different locations of the model were made. Data were processed, determining statistical quantities, wind velocity scales, power density spectra. Data analysis showed different flows patterns for the static and dynamic stall. |
