Influence of Hydrodynamic Damping Model on Dynamic Response of Semisubmersible Floating Offshore Wind Turbine

Abstract In this study, the influence of the hydrodynamic damping models on the floater dynamics of a semisubmersible floating offshore wind turbine (FOWT) was investigated numerically and experimentally. Semisubmersible FOWT substructures typically consist of pontoons and vertical columns. These submerged components exhibit dynamic behavior under the combined influence of waves and currents. The drag force induced by the structure's shape and the damping force caused by fluid viscosity interact in a complex manner, influencing the floater dynamics. During the early design stage, the platform's response characteristics are typically evaluated through integrated load analysis. To better approximate the dynamic behavior observed in the actual structure, it is important to construct a suitable damping model that can represent the real damping characteristics of the system. In this study, a damping model was constructed by integrating results from computational fluid dynamics (CFD) simulations and 1/36-scale model experiments. The linear and quadratic damping coefficients were determined through the results of free decay experiments conducted in still water. The nonlinear Morison drag coefficient was obtained from CFD uniform flow simulation. The characteristics of three models—linear damping, linear-plus-quadratic damping, and Morison drag—were compared, and a method for combining them was proposed. The validity of the combined damping model was confirmed by applying it to the floating substructure.