The anisotropic elastic behaviour of fibre composite material can be used for the coupling of flexural and torsion deformation of rotor blades.
This so-called „aeroelastic tailoring" has been known in aeronautics for some time. However, its application was fairly limited. Efficient fine tuning can reduce the fatigue and extreme loads of wind turbines when blades can be tailored to twist upon deflection.
In his PhD project, Mark Capellaro analyses „Passive Load Control through Bend Twist Coupled Blades". In dynamic simulations of wind turbines he explores the options of controlling the loads by using bend-twist coupled blades and their effect on energy yield. Composite specimen and blade section building will be used to validate the finite element models used in the research. By creating specimens designed to demonstrate bend twist coupling, the accuracy of the coupling stiffnesses created in the finite element stage of the research.
The goal of the research is to demonstrate the effectiveness of passive load reduction of the wind turbine through the use of bend twist coupling in the wind turbine's blades. This is a cooperative project of the SWE and the Department of Composite Technology at the „Institute of Aeronautics and Aircraft Design" (IFB).

The simulation methods being used to analyse the dynamics of wind turbines are using fairly simplistic models. The structural models employ only few modal degrees of freedom, and the "Blade Element Momentum Theory" from rotor aerodynamics can only applied with a considerable number of empirical corrections.

In his research project "Rotor Aerodynamic and Aeroelastic Effects on the Structural Dynamics of Wind Turbines", Stefan Hauptmann enhances existing simulation methods by embedding the multi-body simulation software SIMPACK and extended aerodynamic and aeroelastic calculation methods (CFD, vortex-lattice methods). This allows for a more exact description of particular aerodynamic states, of the dynamics of the system as a whole, and of the loads of the components and their interaction. The systematic comparison of the application of different structural and aerodynamic models within a single simulation environment provides the basis for a systematic analysis of aeroelastic influences for different wind turbine concepts and operating conditions. The use and development of CFD-routines is a joint initiative with the Institute of Aero- and Gasdynamics. Over and above the development of a next-generation simulation computer programme this work provides knowledge and methods for the design of load-reducing control methods, such as individual pitch and the torsional deflection of large rotor blades.

The complex dynamics of the system as a whole and of its components creates uncertainty with respect to the design assumptions and the expected lifespan of components like the drive train and the pitch and yaw system. Thus, Thomas Hecquet focusses in his PhD thesis on the "Interaction of Wind Turbine Dynamics and Drive Train Components" utilising m ulti-body simulations. He plans on establishing procedures for the ascertaining of design loads and their validation by measurements. In addition, he will research new ideas for both the lowering of design loads and the improvement of the reliability. This project ties in with projects on aeroelastic simulation, individual pitch control and their validation through hardware-in-the-loop testing.