Microtabs for Load Alleviation in Horizontal-Axis Wind Turbines

Research output: Chapter in Book/Report/Conference proceedingConference paper


Aerodynamic load variations caused by the tower of a horizontal axis wind turbine on the rotor blades, known
as tower shadow effect, were reproduced and studied in the wind tunnel using a setup that mimics the
interaction between the tower and the blade. Tufts were used to visualize and display the change in the flow
pattern between the blade and the tower during the passage of the blade
Experiments were then performed to study the mitigation of the tower shadow effect by using microtabs.
The effect of microtab deployment and retraction on the lift coefficient of a NACA0021 blade was studied
in a series of wind tunnel experiments at a Reynolds number of 130 000. The experiments show an increase
and a decrease in the lift coefficient for a lower and upper surface microtab respectively. The effect of the
microtab depends strongly on the angle of attack.
Results from lift force measurements show that a lower surface microtab can mitigate load variations in
the case of an upwind blade. However, the variations in the lift force in the case of a downwind blade, where
the blade passes through the wake of the tower, are of a different nature. The use of a microtab is not efficient
in this case.
Original languageEnglish
Title of host publicationMicrotabs for Load Alleviation in Horizontal-Axis Wind Turbines
Publication statusPublished - 20 Sep 2018


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