Abstract:

Offshore wind turbines (OWTs) can access abundant offshore wind resources. These devices are trending toward larger sizes, with the next-generation of turbines expected to be 15~20 MW, becoming the largest rotating machines ever constructed. Due to their massive size, model-scale experiments in laboratories are essential for observing and measuring dynamic response under the expected wind and wave conditions. However, model-scale experiments are also subject to scaling laws to maintain dynamic similitude between the model- and prototype-scale forces. Each dynamic force must follow a distinct similitude law based on geometric scale. Since OWTs are subject to multiple dynamic forces from wind, waves, and structure, similitude distortions then arise when scaling with respect to a single similitude law. Real-time hybrid simulation (RTHS) is a numerical-physical approach that partitions a prototype model into numerical and physical models that interact via actuators and sensors in real time. Since RTHS can partition the system dynamics, different similitude laws can be applied in the physical and numerical models, thereby mitigating similitude distortions. For example, a single dynamic force can be scaled in the laboratory at model scale, which is then coupled with a full-scale numerical model representing the remaining dynamic forces. The project goal is to mitigate similitude distortions in model-scale experiments of OWTs subjected to wind and wave loading. The overarching objective is to assess whether RTHS can mitigate similitude distortions across hydrodynamics, aerodynamics, and structural dynamics in OWT applications when an OWT is partitioned into model-scale physical hydrodynamics and the other full-scale numerical dynamics, referred to as hydro-RTHS. Results show that hydro-RTHS can account for motions and forces induced by nonlinear waves in the global response of OWTs. Hydro-RTHS can provide unique experimental datasets for structures subjected to multiple dynamic forces, accounting for physical wave-structure interaction effects while maintaining similitude at the model scale.