A numerical model for fully coupled aero-hydrodynamic analysis of floating offshore wind turbine

Designing floating offshore wind turbine system is a quite challenging task because of the complex environmental loading and complicated coupling effects. In the present study, the fully coupled aero-hydrodynamic model for numerical simulation of floating offshore wind turbine (FOWT) is established with open source tool OpenFOAM. The coupled FOWT-UALM-SJTU solver is developed using the open source CFD package OpenFOAM, in which the unsteady actuator line model (UALM) is introduced into OpenFOAM for the aerodynamic simulation of wind turbine, while the hydrodynamic computation of floating platform is carried out with a two-phase CFD solver naoe-FOAM-SJTU. In the coupled model, the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations are solved with the turbulence model k-omega SST employed for closure of RANS equations, and the Pressure-Implicit with Splitting of Operations (PISO) algorithm is applied to solve the pressure-velocity coupling equations. The coupled responses of a FOWT with NREL-5MW baseline wind turbine mounted on a semi-submersible platform are investigated. From the simulation, aerodynamic forces including the unsteady aerodynamic power and thrust can be obtained, and hydrodynamic responses such as the sixdegree-of-freedom motions of the floating platform and the mooring tensions are also available. The impact of dynamic motions of floating platform on the aerodynamic performance of wind turbine is analyzed, and the effect of the aerodynamic forces on the hydrodynamic response of the floating platform is also studied.