Stall Flag, Prior Development and First Results. Aiming at Visualisation of the211 Stalled Area on Full Scale Wind Turbines

摘要

Presently even the most sophisticated predictions of the stall behavior of211u001ecommercial wind turbines are often bad. Therefore a new method to visualize stall 211u001ewas developed. The method is based on a very thin detector, the so called 'stall 211u001eflag', that provides a clearly visible signal that shows whether the flow over 211u001ethe stall flag is reversed (stalled) or not. The stall flags operate passively, 211u001econtact less and have a fast response, they can be seen as advanced tufts. Their 211u001eweight is about 1 g and they can be seen clearly from the ground. The stall flags 211u001edo not limit the operational range of the turbine under study. To equip the 211u001eturbine with stall flags taken only several hours, installation of a rotating 211u001ecamera is not required. Stall flags have the potential to visualize the complete 211u001estalled area on commercial rotors. ECN applied for a patent on the stall flag. 211u001eThis report starts with the arguments to develop the stall flags. Then the design 211u001eof the stall flag and the optial details on the visualization method are 211u001epresented. Also the first results of the application of stall flags on turbines 211u001ein the fields will be described. Among these results are high quality photographs 211u001eof the area of reversed/radial flow on a 10 m diamter wind turbine and several 211u001etest pictures of the Rotorline 32 rotor of the Nedwind 30 wind turbine.