Multi-rotor-based real-time hybrid model tank testing of a 10-MW semi-submersible offshore floating wind turbine

Traditional model test faces challenges such as scale effects, difficulties in reproducing turbulent wind, and the inability to simulate shutdown conditions. To address these issues, a 10 MW semi-submersible offshore floating wind turbine was selected as the research subject. An innovative real-time hybrid model test based on a multi-rotor loading device is proposed. The development process of the numerical substructure, the design and control of the loading device has been made public. The physical substructure was designed at a 1:75 scale and installed in a wave tank, where free decay, regular wave, only wind, combined wind and irregular wave, and shutdown tests were conducted. Experimental data were compared and analyzed against simulation results. In the wind test results, the maximum deviation in the mean aerodynamic load across different directions was only 2.59%, indicating that the developed multi-degree-of-freedom loading device effectively reproduces turbulent wind loads. In the two repeated combined wind-wave tests, the average errors for platform surge, pitch, heave motions, and mooring tension were found to be within 2.12%, indicating that repeatability is exhibited by the developed hybrid model test technology. The hybrid experimental method developed in this study simulates the shutdown operating conditions of offshore wind turbines, the study reveals that under parked conditions, the proportion of wave frequency in the platform motion response power spectrum increases significantly. The motion response of offshore wind turbines, induced by impact loads during shutdown, provides valuable insights for the design of offshore wind turbines.