Improvement of Restoring Force in MPS-Based Upending Simulations of a Spar-Type Floating Offshore Wind Turbine
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Floating offshore wind power generation has attracted considerable attention as a technology that enables large-scale wind energy production even in deep-water regions. Spar-type floating offshore wind turbine platforms require an upending process during the construction phase, in which the floater transitions from a horizontal to an upright configuration. During this process, complex fluid–structure interaction behavior arises due to ballast water injection into the floater and changes in the center of gravity, creating a strong demand for accurate numerical simulation methods [1]. In this study, the upending behavior of a spar-type floating body is numerically reproduced using a particle-based fluid-rigid body coupling approach [2, 3]. In the existing model, the ballast water inside the spar and the surrounding water in the experimental tank are computed independently, and the equations of motion of the spar are solved by coupling the internal and external fluid effects at each time step. However, simulations that take ballast water into account revealed that, even under conditions where the spar should theoretically reach a stable upright configuration, it does not become fully vertical and instead comes to rest in a slightly inclined state. To address this issue, this study improves the evaluation method of the restoring force acting on the spar. Numerical results obtained using the improved method are compared with experimental results to examine the validity of the proposed approach.
