A simplified method for coupled analysis of floating offshore wind turbines

The coupled analysis of floating wind turbines is time consuming. This article presents a simplified approach for dynamic response analysis of floating wind turbines that are subjected to wave and wind loads. The goal of the approach presented here is to investigate a simplified method for the aerodynamic forces to minimize the computational time while maintaining acceptable accuracy. Hence, the simplified method is validated against a comprehensive aero-hydro-servo-elastic approach. A dynamic link library (DLL) called "TDHMILL" provides the aerodynamic loads as an external input to the Simo-Riflex. The coupled Simo-Riflex-TDHMILL, "SRT", is compared with the HAWC2 code for spar-type wind turbines. The agreement between the SRT and HAWC2 codes is very good. The hydrodynamic code-to-code comparison between the Simo-Riflex and HAWC2 codes is carried out before the coupled wave-wind-induced analyses. The results show that the codes agree for the wave-only case, as well as for the wave- and wind-induced cases. The statistical characteristics of the dynamic motions and structural responses are compared for spar-type wind turbines. Two spar-type wind turbines are considered in the present article to investigate the sensitivity of the method to different designs. The code-to-code comparison between the SRT and HAWC2 codes is satisfactory for both the ShortSpar and DeepSpar configurations, at moderate and deep water depths, respectively. The simplified approach is intended and suitable for feasibility and pre-engineering studies of alternative substructures where effects from rotor dynamics are of minor importance. The results show that the simplified method is faster than the comprehensive method by a factor of 100, while its accuracy is acceptable in comparison to the sophisticated analyses. (C) 2012 Elsevier Ltd. All rights reserved.