The simulation of dynamic responses based the OC3-hywind spar dominated by the mooring system in quasi-static state

This study discusses the real-Time motion responses of OC3-Hywind spar in waves based on the modular design system, composed of NEMOH and WEC-SIM. in the time-domain simulation, both of the radiation and the diffraction method are used to obtain the hydrodynamic forces from frequency-domain Boundary Element Method (BEM) solver. In order to simulate the system dynamics of OC3-Hywind spar, the Cummins time-domain equation is adopted by solving the governing equations in 6 Degrees-of-Freedom (DOF) motions. Besides, an indicator, Response Amplitude Operator (RAO), is considered to realize the resonance period of OC3-Hywind spar by performing regular wave simulations at various frequencies. Since the RAO peak corresponds to the resonance period of OC3-Hywind spar, it can be used to estimate the spar's response to waves in case of the mooring system. Subsequently, the results present that the quasi-static mooring system is applicable to the estimation of mooring forces as well as the restriction of the wind float in large motion responses. By comparing our model results with other published results of OC3-Hywind spar, it is verified that the calculation of hydrodynamic coefficients and related motion responses is reliable. Eventually, this study would provide a valuable concept in modular designs and help realize hydrodynamic characteristics of wind floats in engineering practice.