On the size effects of toroidal tuned liquid column dampers for mitigating wind- and wave-induced vibrations of monopile wind turbines

The toroidal tuned liquid column damper (TTLCD) can be applied in flexible structures to improve the structural dynamic responses. This study focuses on the impact of size effects of TTLCD on the control efficiency. Two types of size effects are experimentally addressed using the real-time hybrid simulation (RTHS) technique: (1) the effects of experimental scale, and (2) the effects of length ratio. A large number of RTHSs are performed, in which a monopile wind turbine is numerically simulated as the numerical substructure, and five TTLCDs with various experimental scales or length ratios are experimentally tested as the physical substructure. The RTHS results show that the effects of experimental scale on the control efficiency and liquid response are insignificant, and a larger length ratio leads to a stronger performance. Besides, the TTLCD is found to be an efficient additional damping device in monopile wind turbines. The comparison between the RTHS results and the simulation results from a theoretical model is made, and it demonstrates that the theoretical model can capture the dynamic interaction process between the structure and TTLCD with good accuracy.