AIAA Conference Proceedings January 7, 2010
Authors: G. Pechlivanoglou, J. Wagner, C. N. Nayeri, C.O. Paschereit

The implementation of an innovative aerodynamic control technique in wind turbines is
a point under extensive investigation since the conventional wind turbine blade technology
is reaching its limits. Almost all the effort of the wind turbine industry in the field of
aerodynamics is related to the development of blades which offer better performance,
increased reliability and faster control of larger wind turbines. Currently, however, most of
the research effort is focusing on the implementation of aerodynamic elements for dynamic
load alleviation during wind turbine operation rather than rotor stall control or even more
the complete wind turbine power regulation which is the ultimate target of the current
project. The current document presents the test process, methodology and results of
wind tunnel test campaigns on the investigation of the flexible flap configuration as a
possible means of aerodynamic control of wind turbines. The test campaign took place
at the HFI/TU Berlin wind tunnel. Measurements were performed with a model of the
DU96W180 airfoil as well as with the modified-DU96W180 test airfoil section equipped with
the flexible flap assembly in flow with Reynolds number Re equal to 1,300,000. The The
flexible flap was tested in various positive and negative deflections in order to extract its
complete operational curve. The results showed significant influence on both lift and drag
as well as strong variations on the pitch behavior of the wing. The paper also discusses the
possible benefits of the integration of flexible flap systems in wind turbine blade structures.