NON-LINEAR 3D HYDRODYNAMICS OF FLOATING WIND TURBINE COMPARED AGAINST WAVE TANK TESTS

摘要

Assessment of wave-structure interaction in terms of combined hydrodynamic stability and structural survivability is paramount in extreme wave conditions. Components of CFD methodologies needed for accurately capturing the detailed motion of a floating wind turbine (FWT) in survival sea-state is the focus of the study. Physical wave tank tests of a Tension Leg Platform (TLP) concept with four moorings are applied as a first validation, due to its simplicity from a CFD point of view. Two different codes have been objects of study, namely the open source code OpenFOAM® with a flexible mesh approach and the commercial CFD code StarCCM+ with the overset mesh method. The influence of the surface capturing algorithm (VOF method) and the two-way coupling of the six degrees-of-freedom body motion solver and the hydrodynamic solver have been identified as the crucial components in CFD simulation of the FWT. A major advantage of StarCCM+ was that it does not suffer from the same sensitivity as OpenFOAM to the fact that motion of the floating body is strongly coupled to the solution of the hydrodynamics (a stiff FSI problem) which led to instability of the numerical solution. The results obtained with StarCCM+ are comparable with the measured motion of and tension forces on the TLP in both in regular waves and irregular waves.