Dynamic response characteristics of the taut mooring system for integrated renewable energy devices

The safety of mooring system is critical for the floating renewable energy devices. The performance of one taut mooring system, designed for keeping the position of integrated devices, is experimentally investigated in both regular and irregular waves, taking into account the effects of the incident wave angle, the PTO damping force and the heaving point absorbers. It reveals that a local maximum and minimum, indicating the high-frequency oscillation, appear within each cycle of taut mooring loads. Meanwhile, in the frequency domain, the multiple spectral peaks and a downshift of high-order peak frequencies can be detected with the intensified vibration. At specific incident angles, the snap load can be triggered more easily in the same sea state, accompanied with the appearance of slow-drift motion of the integrated device. The PTO damping force can significantly change the performance of mooring lines at the initial loading stage and the mechanism involved for each mooring line can be totally different. The layout of split floaters with respect to the incident wave mainly affects the motion-induced component of maximum mooring loads, without significantly change the oscillation-induced ones. Under certain conditions, the mutual inhibition effect between wave-frequency and high-frequency load components can be detected for the same mooring line.