Time resolved identification of aerodynamic extreme events and unsteady effects under turbulent inflow conditions

• Applicants: Dr. Michael Hölling; Professor Dr. Joachim Peinke
• Subject Area: Fluid Mechanics
• Term: from 2012 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 218850002

Wind energy converters are operating within the atmospheric boundary layer (ABL) under turbulent wind conditions. The inherent characteristics of these turbulent wind fields vary and depend strongly on the topography surrounding the wind turbines. The performance of a wind turbine is to a great extend given by the reaction of the aerodynamic design of the blades, in combination with the control system to different turbulent wind conditions. Here, not only the mean power output describes the quality of the performance of a turbine but also the resulting loads as well as extreme loads, which somehow is reflected in the dynamic response of the whole machine. For the design of new large wind turbines a reduction of loads due to the material limits of mechanical strength is desired. Thus, a better understanding of the aerodynamic reaction of rotor blades under turbulent inflow conditions is essential for designing new control strategies and new blades that feature for example smart devices to influence the aerodynamics locally to minimize extreme load events and fatigue loads, respectively. This partner project aims to investigate in detail the flow around airfoils under quasi 2-dimensional turbulent inflow conditions, which reproduce in high quality the atmospheric wind conditions for a real wind turbine. For the inflow conditions the existing active grid in our wind tunnel will be used to generate atmospheric turbulent conditions in a rescaled manner. The scale resolved statistics as well as typical single events like gusts can be generated in a well-defined and reproducible way. Different measurement techniques in combination with state of the art analyzing tools will be used to pinpoint aerodynamic extreme events and unsteady effects on a blade segment. The central research idea of this project is to achieve a deeper understanding of the interaction between turbulent inflow conditions and the nonlinear aerodynamic instabilities evolving around a rotor blade. Thus the correlation between turbulent inflow including aerodynamic extreme events and the unsteady effects on a rotor blade shall be investigated. A high-speed stereo PIV (particle image velocimetry) system will be used to gather time resolved spatial information of the flow around the airfoil. Simultaneously forces measurements are planned. With a combination of imagine processing and stochastic methods we aim to identify leading aerodynamic phenomena causing the main loads on the rotor profiles.

• DFG Programme: Research Grants