Real-time hybrid model tank testing for aero-hydro-servo-elastic assessment of a monopile offshore wind turbine

Abstract

Physical model-scale testing could assist in identifying important coupling effects and validating numerical simulations. However, the requirement regarding the dynamic similarity for the offshore wind turbine model is difficult to meet due to the scaling effects. To address this challenge, a testing method is proposed, using a linear actuator to reproduce the required aerodynamic force for the real-time hybrid model test. The magnitudes of the applied force were simulated using a numerical substructure developed based on the aerodynamic coupling analysis. This paper designed the physical substructure of offshore wind turbines, selected the "Hardware in the Loop" method, and conducted relevant experiments in a wave tank. The turbulent wind and pitch control were reproduced during the testing process. The experimental data and simulation results were compared and analyzed. The maximum error of the average values of different physical quantities (Rotor thrust force, Tower top displacement) measured was 5.51 %, while the maximum error in the standard values was −10.59 %. The data indicate good consistency between the experimental and simulation results. From the analysis of power spectral density (PSD) results of different physical quantities, it was found that turbulent wind provides significant excitation and energy in the frequency range below wave excitation. The frequency of turbulent wind loads hides the low-frequency second-order wave forces, indicating the necessity of reproducing turbulent winds in experiments. The real-time hybrid model test method can accurately reproduce the turbulent wind load, achieve the combined action of random wind and waves, and improve the model testing level of existing monopile offshore wind turbines.