In the design and optimization of Floating Wind Turbines (FWTs), there are challenges related to the large number of design parameters and the need for efficient and accurate calculation of turbine dynamic responses. ...
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In the design and optimization of Floating Wind Turbines (FWTs), there are challenges related to the large number of design parameters and the need for efficient and accurate calculation of turbine dynamic responses. To address these issues, this study proposes a surrogate model-assisted evolutionary framework for the mooring system optimization of shallow-water wind turbines. This distinct feature of the optimization framework lies in that it employs a sparse polynomial chaos expansion surrogate model to quickly predict the performance indicator values of FWTs with different mooring configurations and adopts the differential evolution algorithm to find the mooring parameter combination with the best performance, achieving efficient, accurate, and automated multi-parameter optimization. The framework is utilized to optimize the mooringsystem for a FWT at a relatively shallow water depth, through defining a mooring performance evaluation indicator as the objective function that comprehensively considers mooring line tensions, platform motions, anchor tensions, and the mooring line material cost. Based on the optimization application, the accuracy of the optimization framework is verified. The dynamic responses and safety assessments of the optimized FWT in the fatigue limit state (FLS) and ultimate limit state (ULS) are conducted. The results demonstrate the effectiveness of the proposed optimization framework in enhancing a FWT's performance according to flexibly defined objective functions.
The design of mooringsystems plays a pivotal role in the success of Floating Offshore Wind Turbine (FOWT) projects. This process naturally involves iterations, as design and analysis are intricately linked. Despite t...
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The design of mooringsystems plays a pivotal role in the success of Floating Offshore Wind Turbine (FOWT) projects. This process naturally involves iterations, as design and analysis are intricately linked. Despite the inherent nonlinearity of mooringsystem restoring forces, many designers opt for employing an equivalent linear mooringsystem stiffness matrix to expedite the optimization process in early design stages. This article aims to underscore the limitations associated with relying on the equivalent linear model when compared to accounting for nonlinear restoring forces during optimization processes. To illustrate this point, a case study was conducted using the reference semi-submersible platform VolturnUS-S. The study considered intermediate to large water depths and addressed three different mooring configurations: catenary, semi-taut, and taut lines. The analysis focused on several critical aspects, including offset watch circles, line tensions (including those at the anchors), and a cost estimate based on the different models. The findings indicate that, for catenary-based mooringsystems, the linear model remains a good approximation, leading to no significant loss of accuracy in the context of early design stages. As the lines become tauter, however, the nonlinearities become more pronounced and the errors involved in the linear model can reach unacceptable levels.
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