One issue is the appropriate simulation length needed for floating turbines. The International Electrotechnical Commission's (IEC) 61400-3 design standard covers fixed-bottom offshore wind turbines, but there are a number of new research questions that need to be answered to modify these standards so that they are applicable to floating wind turbines. With the push towards siting wind turbines farther offshore due to higher wind quality and less visibility, floating offshore wind turbines, which can be located in deep water, are becoming an economically attractive option. Finally, we demonstrate the capabilities of the new computational framework by carrying out large-eddy simulation of a floating offshore wind turbine interacting with realistic ocean wind and waves.Īssessing Fatigue and Ultimate Load Uncertainty in Floating Offshore Wind Turbines Due to Varying Simulation Length We validate the model for both simple wave trains and three-dimensional directional waves and compare the results with experimental and theoretical solutions. The large-scale wave field solver is coupled with the near-field FSI solver with a one-way coupling approach by feeding into the latter waves via a pressure-forcing method combined with the level set method. The two-phase flow FSI solver is based on the level set method and is capable of simulating the coupled dynamic interaction of arbitrarily complex bodies with airflow and waves. The large-scale wind-wave interaction model is based on a two-fluid dynamically-coupled approach that employs a high-order spectral method for simulating the water motion and a viscous solver with undulatory boundaries for the air motion. We employ an efficient large-scale model to develop offshore wind and wave environmental conditions, which are then incorporated into a high resolution two-phase flow solver with fluid- structure interaction (FSI). We develop a numerical method for simulating coupled interactions of complex floating structures with large-scale ocean waves and atmospheric turbulence. The stability trends (disturbance modes versus the divergence rate of vortex structures) of the two analyses are compared to identify the impact that above-rated wave-induced structural motions have on the stability of the floating offshore wind turbine wake.įluid- structure interaction simulation of floating structures interacting with complex, large-scale ocean waves and atmospheric turbulence with application to floating offshore wind turbinesĬalderer, Antoni Guo, Xin Shen, Lian Sotiropoulos, Fotis The platform motion is then introduced via synthetic time series, and a stability analysis is performed on the wake generated by the floating offshore wind turbine at the same above-rated inflow conditions. To evaluate the impact of these above-rated conditions, a linear stability analysis is first performed on the near wake generated by a fixed-tower wind turbine configuration at above-rated inflow conditions.
#Orcaflex wamit input series
A synthetic time series of relatively high-amplitude/high-frequency representative of above-rated conditions of the NREL 5MW referece wind turbine is imposed on the rotor structure.
#Orcaflex wamit input free
The rotor near-wake is generated using a lifting-line free vortex wake method, which is strongly coupled to a finite element solver for kinematically nonlinear blade deformations. The impact of above-rated wave-induced motions on the stability of floating offshore wind turbine near-wakes is studied numerically. The results indicate that the semi-submersible concept has excellent performance and SESAM could be an effective tool for floating wind turbine design and analysis.Īeroelastic impact of above-rated wave-induced structural motions on the near-wake stability of a floating offshore wind turbine rotor
The effect of change in environmental conditions on the dynamic response of the system under wave and wind loading was examined. The wind turbine was modeled as a wind block with a certain thrust coefficient, and the hydrodynamics and mooring system dynamics of the platform were calculated by SESAM software. This paper describes a numerical model to simulate dynamic behavior of a new semi-submersible type floating offshore wind turbine (FOWT) system. The performances of motion and mooring system dynamics are vital to designing a cost effective and durable floating platform. However, countries with limited shallow water areas require innovative floating platforms to deploy wind turbines offshore in order to harness wind energy to generate electricity in deep seas. The development of offshore wind farms was originally carried out in shallow water areas with fixed (seabed mounted) structures. Motion performance and mooring system of a floating offshore wind turbine