Dynamic response of floating substructure of spar-type offshore wind turbine with catenary mooring cables

The station keeping and the rotational oscillation control are important to secure the dynamic stability of spar-type floating offshore wind turbine subject to irregular wind and wave excitations. Those are usually evaluated in terms of rigid body dynamic response of floating substructure which supports whole offshore wind turbine. In this context, this paper addresses the numerical investigation of dynamic response of a spar-type hollow cylindrical floating substructure moored by three catenary cables to irregular wave excitation. The upper part of wind turbine above wind tower is simplified as a lumped mass and the incompressible irregular potential wave flow is generated according to the Pierson-Moskowitz spectrum. The wave-floating substructure and wave-mooring cable interactions are simulated by coupling BEM and FEM in the staggered iterative manner. Through the numerical experiments, the time- and frequency-responses of a rigid spar-type hollow cylindrical floating substructure and the tension of mooring cables are investigated with respect to the total length and the connection position of mooring cables.