This work represents a contribution to the 1st FOWT Comparative Study. The Reynolds-averaged Navier-Stokes solver, interFoam, is used to simulate the hydrodynamic response of a 1:70 scale model floating offshore wind turbine in load cases including static equilibrium, decay tests in heave, surge and pitch as well as two focused wave events. Mesh deformation is used to accommodate the body motion and the catenary moorings are modelled using a quasi-static method. Wave generation and absorption is achieved via relaxation zones. The numerical solutions are compared with the available physical measurements and are shown to agree well for heave motion but significant differences are present for the other degrees of freedom and the mooring line loads.
This paper details one contribution to the 1st FOWT Comparative Study (Ransley et al. 2022), on the hydrodynamic response of a floating offshore wind turbine (FOWT), using the open-source computational fluid dynamics (CFD) software, OpenFOAM.
In the field of offshore engineering, numerical modelling has become an integral part of the research, design and innovation (RD&I). However, accurate modelling of the associated fluid-structure interaction problems is challenging and can be computationally expensive (prohibiting its routine use by industry). As a result, a wide range of numerical tools exists, in which developers apply various levels of approximation to the governing equations in order to, effectively, balance the required physical accuracy of the model with its computational efficiency. However, when it comes to numerically predicting the response of moored floating platforms, under complex environmental loads, considerable uncertainty remains and it is not yet clear which numerical method, and what level of approximation, is most appropriate. As a result, a lack of confidence in the reliability of numerical solutions, limits the value numerical modelling can add to industry practices. This has, arguably, led to over-engineering of platform concepts, to mitigate risk, and higher overall costs (which is particularly problematic for offshore renewable energy applications, like floating offshore wind, where the margins, associated with the cost of energy, are very tight).
