Partitioned coupling of fluid-structure interaction for the simulation of floating wind turbines

Abstract

Fluid-structure interaction problems appear in many different fields of application. An interesting and highly topical field is offshore renewable energy. An increasing energy demand, limited fossil energy sources and the climate change in combination with limited suitable and available space ashore lead to an increased relevance of offshore renewable energy. A promising offshore renewable energy concept is the use of floating wind turbines. For the simulation of floating wind turbines, the necessary and computationally expensive fluid-structure interaction coupling has to be combined with large domains, highly nonlinear and dynamic structural behavior and complex flow situations. This requires new and innovative techniques in the solution process. In this work, the partitioned solution utilizing existing field solvers is suitable for this type of problem due to the availability of well-developed fluid and structural solvers. To manage the partitioned coupling, the in-house C++ library comana is employed. This coupling framework is employed to control the iterative solution process and to perform the necessary exchange of surface quantities on the interface between the fluid and structural field of the fluid-structure interaction problem. Through this, comana enables the computation of complex strongly coupled fluid-structure interaction problems within a reasonable amount of time. Despite the necessary changes for the partitioned coupling, the modifications to the existing specialized high-fidelity fluid and structural solvers are minimized to maintain their sophisticated solution techniques. The partitioned coupling procedure is described and simulation results are presented. Different measures to accelerate, stabilize and improve the solution of this fluid-structure interaction problem are demonstrated. Among these measures are the prediction and the convergence acceleration in the implicit coupling of the fluid and structural field solvers. In the scope of a future research project, the presented method will be applied to develop the simulation of a point wave energy absorber used for the conversion of wave energy into electric energy.