Abstract
The influence of 3 MW Hywind-II wind turbine wakes from an upstream offshore floating wind turbine on a downstream turbine with a separation distance of seven rotor diameters was studied for a site in the Gulf of Maine. The turbines and the platforms were subjected to atmospheric boundary layer flows. Various sensitivity studies on fatigue loads with respect to the positions of the downstream turbine were performed and validated with a large-eddy simulation tool. In particular, the effect of various lateral positions of the downstream turbine relative to the upstream turbine were considered using time-series turbine wake data generated from the large-eddy simulation tool which served as an input to an aero-elastic wind turbine model to assess the loads. The load response from the rotor, tower, and the floating platform for the downstream turbine were sensitive to the lateral offset positions where turbines that were partially exposed to upstream turbine wakes yielded significant increases in the cyclic load range. For the given set of lateral positions for the downstream turbine, the largest damage equivalent load occurred when the turbine was one rotor diameter to the left of the centerline, when looking upstream, which is the position of the turbine fully exposed to upstream turbine wake. On the other hand, the fatigue load on the downstream turbine placed on the right side of the position fully exposed to the upstream turbine wake, yielded lower stress due to the non-symmetric shape of the turbine wake. The configuration associated with the largest damage equivalent loads was further investigated in a large-eddy simulation, modeling both the upstream and downstream turbines. It was found that the energy spectra at the blade rotational frequency were a magnitude order higher for the downstream turbine, especially for surge, heave, pitch, and yaw motion of the platform. The increase of the damage equivalent load for the flapwise blade root moment was 45% compared to the upstream turbine, which can potentially reduce the turbine service life time.
Highlights
The present study investigates the influence of turbine wakes originating from an upstream offshore floating wind turbine (OFWT) on a downstream turbine for a site in the Gulf of Maine.The rated power of the wind turbine is 3 MW, which is supported by a Hywind-II [1] floating spar platform anchored with chain catenary moorings and drag embedment anchors at 140 m water depth
Because analytical tools to calculate wake deficits in large wind farms are based on empirical formulas that do not catch the true essence of the wake field, a wind turbine structural analysis program (FAST [2]) is coupled to a computational fluid dynamics (CFD) program to compute the turbulence intensity of a floating offshore wind turbine farm
A large-eddy simulation of an atmospheric boundary layer with two 3 MW turbines on a floating spar platform (Hywind-II) was studied to investigate the impact of a wake generated from the spar platform (Hywind-II) was studied to investigate the impact of a wake generated from the upstream upstream turbine (WT1) on the downstream turbine (WT2)
Summary
The present study investigates the influence of turbine wakes originating from an upstream offshore floating wind turbine (OFWT) on a downstream turbine for a site in the Gulf of Maine. Several mid-fidelity wind turbine wake models have been employed using the free vortex method (FVM) [15] to improve the calculations of the wind-wave induced platform motion coupled with the induction produced by the turbine rotor Another FVM was used [16] to enhance the predictive capability of modeling the OFWT from the traditional blade-element momentum theory. The present study employs a high-fidelity tool based on a large-eddy simulation approach in which a coupled fluid-structure interaction tool has been applied to a study of floating offshore wind turbines. A large-eddy simulation in data ata 7D downstream from theinteraction turbine totool use has as anbeen input to FAST from SOWFA which coupled fluid-structure applied to a(one-way study of coupling floating offshore wind to FAST); The (2) conduct of various positionssteps: using(1).
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