Prediction of wind loadings on offshore wind turbines using CFD

Analysing the structural response of offshore wind turbines (OWTs) requires a robust method to estimate environmental loadings associated with extreme weather conditions. This study aimed to accurately predict wind loadings on a non-rotating OWT using a Computational Fluid Dynamics (CFD) code, Ansys Fluent package. The inlet velocity boundary condition was defined as a uniform inlet wind speed and then as a Normal Wind Profile (NWP). Three large wind speeds of 25 m/s, 40 m/s and 50 m/s were tested with the aid of the RANS equations and the Shear Stress Transport (SST) turbulence model. A thorough mesh convergence study was conducted for both 2D and 3D simulations, and their results were assessed using the Richardson extrapolation method. Overall, the NWP method was found to produce larger wind forces and moments in comparison with the uniform wind speed conditions (on average 52% and 63% higher, respectively), and its predictions were consistent with the estimations obtained using the simplified drag formula recommended by offshore standards (within approx. 7% difference for wind forces). This paper provided the preliminary steps towards investigating the structural integrity of OWTs under extreme weather conditions.