Added damping of a wind turbine rotor: Two-dimensional discretization expressing the nonlinear wind-force dependency

In determining wind forces on wind turbine blades, and subsequently on the tower and the foundation, the blade response velocity cannot be neglected. This velocity alters the wind force, which depends on the wind velocity relative to that of the blades This blade response velocity component of the wind force is commonly referred to as added...

Aerodynamic damping of nonlinearily wind-excited wind turbine blades

This paper presents the first step of the derivation of an aerodynamic damping matrix that can be adopted for the foundation design of a wind turbine. A single turbine blade is modelled as a discrete mass-spring system, representing the flap and edge wise motions. Nonlinear wind forcing is applied, which couples the degrees of freedom. The...

Preliminary design of offshore wind turbine support structures: The importance of proper mode shape estimation

Offshore wind turbines are highly exposed to timevarying loads. For support structures, estimation of the fatigue damage during the lifetime of the structure is an essential design aspect. This already applies for the preliminary design stage. In determining the dynamic amplification in the frequency domain, modal analysis is a common tool. This...

Operational Vibration-Based Response Estimation for Offshore Wind Lattice Structures

The design for fatigue for offshore wind turbine structures is characterized by uncertainty, resulting from both loading specifications and numerical modelling. At the same time, fatigue is a main design driver for this type of structures. This study presents a strategy to monitor the accumulated fatigue damage in real-time, employing a joint...

Estimation of accumulated fatigue damage in lattice support structures from operational vibrations

Support structures of offshore wind turbines are prone to failure from fatigue damage. The design for fatigue requires accurate predictions of the environmental conditions and an adequate definition of the structural properties, valid for the entire design life-time. Estimates of the accumulated fatigue damage are, however, characterized by a...

On the feasibility of monopile foundations for offshore wind in the Baltic Sea

For the design of offshore foundations in regions such as the Baltic Sea, it is paramount that ice-structure interaction is appropriately considered. For the monopile, a common foundation for offshore wind turbines, challenges with ice-induced vibrations and high ridge loads may require ice-mitigating measures to be included in the design. A ...

State-independent apparent aero-elastic properties of wind turbine rotors: A method for the preliminary design of offshore wind support structures

In the previous decade, offshore wind undeniably took off as an important player in the European energymarket, which resulted in continuously enhancing turbine sizes and foundation structures pushing the boundaries of engineering, with the purpose of minimizing the levelized cost of energy to the range of optimal competitiveness. Regarding the...

Coupled flap and edge wise blade motion due to a quadratic wind force definition

The wind force on turbine blades, consisting of a drag and lift component, depends nonlinearly on the relative wind velocity. This relative velocity comprises mean wind speed, wind speed fluctuations and the structural response velocity. The nonlinear wind excitation couples the flap wise and edge wise response of a turbine blade. To analyze...

A low-fidelity model for the dynamic analysis of full-lattice wind support structures

This work aims to develop a low-fidelity model for a lattice support structure for offshore wind applications. The proposed low-fidelity model consists of a sequence of regular Timoshenko beams, each of them characterized by homogenized mechanical and mass properties representative of the single bays of the reference space-frame structure....

Comparative analysis of offshore support structures for two-bladed large wind turbines (10+MW) in deep waters

The offshore wind market is developing towards exploiting wind resources in deeper water sites. Inevitably, this fuels new research and feasibility studies on alternative solutions for the wind turbine support structures. Within this context, this work aims at comparing three different support structure design concepts for a 14 MW two-bladed...

Tower shadow excitation of a downwind rotor blade of a turbine with a tubular tower

The downwind configuration of wind turbines offers benefits regarding the blade-tower clearance, as during operation the blade primarily bends away from the tower. Consequently, the blades can be designed with lower stiffness. For tubular towers, however, a significant deficit of the wind speed in the tower wake occurs, resulting in fatigue...

Decoupled Modelling Approaches for Environmental Interactions with Monopile-Based Offshore Wind Support Structures

To meet the political goals regarding renewable energy production, offshore wind keeps expanding to waters with larger depths and harsher conditions, while the turbine size continues to grow and ever-larger foundation structures are required. This development can only be successful if further cuts in the levelized cost of energy are established....