Numerical verification of the dynamic aerodynamic similarity criterion for wind tunnel experiments of floating offshore wind turbines

Abstract

Model tests and real-time hybrid simulation tests of floating offshore wind turbines have recently been extensively conducted to explore the aero-hydro-servo-elastic coupling mechanism. The traditional thrust similarity criterion under the Froude scale cannot satisfy the dynamic aerodynamic similarity in the wave basin experiments. Meanwhile, the traditional model wind turbine in model tests shows huge differences in Reynolds number and significant deviations in the optimal tip speed ratio, and the dynamic performance is different from that of the prototype wind turbine. Therefore, a new criterion based on the mapping of the optimal tip speed ratio is proposed, and a new model wind turbine is designed to physically reproduce the dynamic aerodynamics of the prototype wind turbine accurately in wind tunnel experiments. Then the dynamic aerodynamic similarity in this criterion is numerically verified and compared with that in the traditional criterion. The simulation is performed in steady and unsteady inflows by the open-source OpenFAST. The platform motions of the prototype and model wind turbine are inflow-motivated and program-forced, respectively. The calculation results show that the dynamic thrust, power and their coefficients in the new criterion all maintain better similarity compared to those in the traditional criterion. This study is important for wind tunnel model tests and RTHS tests to accurately obtain unsteady aerodynamics, and it can guide the aero-hydro-structure load evaluations and turbine-floater-mooring integrated designs for large-scale floating offshore wind turbines.