Abstract
AbstractOffshore wind turbines have the potential to capture the high‐quality wind resource. However, the significant wind and wave excitations may result in excessive vibrations and decreased reliability. To reduce vibrations, passive structural control devices, such as the tuned mass damper (TMD), have been used. To further enhance the vibration suppression capability, inerter‐based absorbers (IBAs) have been studied using the structure‐based approach, that is, proposing specific stiffness‐damping‐inertance elements layouts for investigation. Such an approach has a critical limitation of being only able to cover specific IBA layouts, leaving numerous beneficial configurations not identified. This paper adopts the newly introduced structure‐immittance approach, which is able to cover all network layout possibilities with a predetermined number of elements. Linear monopile and spar‐buoy turbine models are first established for optimisation. Results show that the performance improvements can be up to 6.5% and 7.3% with four and six elements, respectively, compared with the TMD. Moreover, a complete set of beneficial IBA layouts with explicit element types and numbers have been obtained, which is essential for next‐step real‐life applications. In order to verify the effectiveness of the identified absorbers with OpenFAST, an approach has been established to integrate any IBA transfer functions. It has been shown that the performance benefits preserve under both the fatigue limit state (FLS) and the ultimate limit state (ULS). Furthermore, results show that the mass component of the optimum IBAs can be reduced by up to 25.1% (7,486 kg) to achieve the same performance as the TMD.
Highlights
Offshore wind turbines experience significant loadings from the external metocean conditions including wind, waves, and currents, which can reduce the reliability of the turbines and increase the cost of energy.[1]
Results show that inerter-based absorber (IBA) are more effective in the side-to-side direction, which is thought to be because there is less aerodynamic damping in this direction
IBAs are more effective in the side-to-side direction where the improvement can be up to 3.3%, as there is little aerodynamic damping in this direction
Summary
Offshore wind turbines experience significant loadings from the external metocean conditions including wind, waves, and currents, which can reduce the reliability of the turbines and increase the cost of energy.[1] Load mitigation is a critical strategy to reduce. Lackner and Rotea[5] included passive TMD technology into the FAST code,[6] which is a fully coupled aero-hydro-servo-elastic code developed by the National Renewable Energy Laboratory (NREL) to simulate the loads and performance of offshore wind turbines. Optimum TMD parameter values were investigated based on simplified limited degree-of-freedom (DOF) turbine models[7] developed by Stewart and Lackner,[8] and the effects of wind-wave misalignment on turbines were studied.[8] Si et al[9] established a 5-DOF spar-buoy floating turbine model and investigated the vibration suppression performance of a TMD in the platform. Park et al[12] included a single pendulum TMD in FAST, which can oscillate omni-directionally (i.e., 2-D motion) with different semi-active control strategy
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