Calculation of Hydrodynamic Forces on Floating Offshore Wind Turbines Using an Optimized Morison Inertia Coefficient Method

Abstract Calculating the hydrodynamic force acting on a floating platform is essential for assessing its dynamic behavior. Traditionally, this analysis for floating offshore oil and gas platforms involves three-dimensional diffraction/radiation potential analysis to derive the added mass coefficients, radiation damping coefficients, and wave exciting force coefficients in the frequency domain. These coefficients are then used to compute the dynamic behavior in the time domain, and the same procedure is applied to the substructure of floating offshore wind turbines. However, when the floater’s shape or dimensions change during the initial design stage, the potential analysis must be repeated each time, potentially delaying the design process. This study investigates the use of the Morison model with optimized inertia coefficients as a more efficient method to approximate the hydrodynamic force on a floater without requiring potential analysis in the early design phase of a floating offshore wind turbine. Additionally, we present a procedure for determining the inertia coefficients in the Morison equation and an optimization process to reduce errors relative to the potential analysis results. To validate the proposed method, the dynamic response of a 15 MW floating offshore wind turbine was calculated using the optimized Morison inertia coefficients, and the accuracy of these coefficients was confirmed through comparison with potential analysis results. The results of this study demonstrate that applying the optimized Morison inertia coefficient can predict wave loads at a level similar to that of diffraction/radiation potential analysis, which allows rapid estimation of the dynamic behavior of the floater in the early design stage.