Synthetic jet actuation for load control

H De Vries,E T A Van Der Weide,H W M Hoeijmakers

doi:10.1088/1742-6596/555/1/012026

Abstract

The reduction of wind turbine blade loads is an important issue in the reduction of the costs of energy production. Reduction of the loads of a non-cyclic nature requires so-called smart rotor control, which involves the application of distributed actuators and sensors to provide fast and local changes in aerodynamic performance. This paper investigates the use of synthetic jets for smart rotor control. Synthetic jets are formed by ingesting low-momentum fluid from the boundary layer along the blade into a cavity and subsequently ejecting this fluid with a higher momentum. We focus on the observed flow phenomena and the ability to use these to obtain the desired changes of the aerodynamic properties of a blade section. To this end, numerical simulations and wind tunnel experiments of synthetic jet actuation on a non-rotating NACA0018 airfoil have been performed. The synthetic jets are long spanwise slits, located close to the trailing edge and directed perpendicularly to the surface of the airfoil. Due to limitations of the present experimental setup in terms of performance of the synthetic jets, the main focus is on the numerical flow simulations. The present results show that high-frequency synthetic jet actuation close to the trailing edge can induce changes in the effective angle of attack up to approximately 2.9°.

Highlights

A major goal for the wind energy industry is reduction of the costs of energy production
Increases in lift as well as decreases in lift are needed. Both effects could be generated by synthetic jet actuation, we focus on lift increases here, i.e. positive angles of attack are investigated with synthetic jets located on the lower side of the NACA0018 airfoil
For a real-scale wind turbine blade section, with a chord length at least one order of magnitude larger than that of the present wind-tunnel model, the actuation frequency becomes in the order of 10 Hz

Summary

Introduction

A major goal for the wind energy industry is reduction of the costs of energy production. Important factors affecting these costs are the amount of materials required for the structure, the required maintenance and the reliability of the wind turbine during its life span. One of the contributions to these factors is the design of the wind turbine blades, which is strongly influenced by the fatigue loads they endure. The blades are constantly subjected to changing loads due to variable wind (gusts), turbulent inflow, wind shear, gravity, tower shadow, yaw and wake interaction. Reduction of the loads of a non-cyclic nature (turbulence, wind gusts) requires so-called smart rotor control. Smart rotor control involves the application of distributed actuators and sensors coupled to one or more controllers, providing fast and local changes in aerodynamic performance of the blades

Methods

Results

Conclusion