Comparative study of load simulation approaches used for the dynamic analysis on an offshore wind turbine jacket with different modeling techniques

Abstract

In this paper, the influences of different load simulation approaches and jacket models on the loading and the structural responses of offshore wind turbine (OWT) jackets are investigated. In the first part, the effect of three load simulation approaches used for the dynamic analysis in OWT simulation is compared under different wind and wave conditions. One is the uncoupled method, the second is the sequentially coupled approach and the final one is the fully integrated (coupled) approach. The fully integrated method is with strong coupling and is considered as the reference. The comparison with the other two methods is conducted based on an OWT jacket, which is modeled with pure beam elements. For the comparison of load simulation approaches, the results show that the simulation results of the sequentially coupled approach are mostly in good agreement with those of the fully coupled approach. The uncoupled approach may lead to big errors in the extreme responses of dynamic analysis. Based on this numerical investigation, the sequentially coupled approach is chosen for the following study. In the second part, the influences of the different jacket models on the structural responses are also studied, because the OWT jackets are often modeling with beam elements, which will over/underestimate the responses of the jackets. Two numerical models of the jacket are developed. One is with pure beam elements (Beam model), while the second is with more advanced modeling by using super-elements (Super-element model). The sequentially coupled load simulation approach is applied for both the two jacket models. For the comparison between the two jacket models, the responses of the super-element model are different from those of the beam model, especially in the jacket displacement. Hence, from this study, the fully and sequentially coupled approaches are recommended for offshore load calculations and the super-element model is recommended for better modeling the jacket behaviors.