Wind-Turbine Vibration Reduction Using Flow Control Devices

The size of wind turbine blades has been continuously increased for better aerodynamic efficiency. However, the large scale blades induce loud noise and vibration as well as the increased difficulty in maintenance; all of these eventually causes the increase in the cost of energy. The vibration of wind turbines is mainly caused by wind turbulence, wind shear, and tower shadow. These causes change in local angle of attack of wind turbine blades and create mostly periodic vibration. In this work, a flow control device is applied for vibration reduction of wind turbine blades. The conventional role of flow control devices is to increase lift coefficient and to reduce drag coefficient by flow separation delay. In this research, flow control device is used to make a flat slope of lift coefficient in specific angle of attack range for vibration reduction; lift coefficient is not always increased but also decreased, too. To manipulate the lift coefficient slope, several types of flow separation controller are considered. Finally, a plasma actuator is selected because the minimal structural modification is necessary while providing sufficient lift coefficient control. The plasma actuator is attached to an airfoil to blow the jet upwind to decrease the lift. Computational fluid dynamics simulation is conducted to estimate the flow control performance of the plasma actuator. Experiments are conducted on a DU35-A17 airfoil to verify the lift coefficient manipulation performance of the plasma actuator.