Abstract:A free-vortex wake (FVW) model is developed in this paper to analyse the unsteady aerodynamic performance of offshore floating wind turbines. A time-marching algorithm of third-order accuracy is applied in the FVW model. Owing to the complex floating platform motions, the blade inflow conditions and the positions of initial points of vortex filaments, which are different from the fixed wind turbine, are modified in the implemented model. A threedimensional rotational effect model and a dynamic stall model are … Show more
“…In the 6‐line anchor system, the turbine spacing is 838 m, and wake effects are not negligible in this case. For example, the decrease in wind speed due to wake effects from 11.4 to 9 m/s would decrease the rotor thrust from 800 kN to roughly 500 kN in DLC 1.6 for the 6‐line anchor system. Including wake effects in this stage significantly increases the number of permutations of conditions with WWC directions; therefore, they are not considered in this study.…”
Floating offshore wind energy has seen significant progress, evidenced by multiple demonstration projects and the first floating wind farm (Hywind Scotland). However, the high capital cost associated with floating wind development remains one of the primary hurdles in the industry's growth. In efforts to lower this cost, this paper investigates a novel shared anchor concept to reduce the total number of anchors and installations. Two different multiline geometries are studied-a 3-line anchor system and a 6-line anchor system. Simulations of the anchor forces are generated using National Renewable Energy Laboratory's OC4-DeepCwind semisubmersible floating system and 5-MW wind turbine, and the anchor forces of the 2 different multiline geometries are compared to those of a conventional single-line anchor geometry.Multiline anchor net force is calculated by vector summing the contributing tensions of the lines connected to the anchor. Results show that the behavior of the multiline anchor net force is governed by the connected line contributing the largest tension.Mean and maximum anchor forces are decreased in the 3-line anchor system and increased in the 6-line anchor system, relative to the single-line system. The average direction of multiline anchor net force is aligned with environmental load direction, and a wider range of multiline anchor net force directions are exhibited for wavedominated load cases. Direction reversal of the multiline anchor net force under constant wind, wave, and current direction is small and infrequent. These force direction results reveal that a multiline anchor must have axisymmetric strength.
“…In the 6‐line anchor system, the turbine spacing is 838 m, and wake effects are not negligible in this case. For example, the decrease in wind speed due to wake effects from 11.4 to 9 m/s would decrease the rotor thrust from 800 kN to roughly 500 kN in DLC 1.6 for the 6‐line anchor system. Including wake effects in this stage significantly increases the number of permutations of conditions with WWC directions; therefore, they are not considered in this study.…”
Floating offshore wind energy has seen significant progress, evidenced by multiple demonstration projects and the first floating wind farm (Hywind Scotland). However, the high capital cost associated with floating wind development remains one of the primary hurdles in the industry's growth. In efforts to lower this cost, this paper investigates a novel shared anchor concept to reduce the total number of anchors and installations. Two different multiline geometries are studied-a 3-line anchor system and a 6-line anchor system. Simulations of the anchor forces are generated using National Renewable Energy Laboratory's OC4-DeepCwind semisubmersible floating system and 5-MW wind turbine, and the anchor forces of the 2 different multiline geometries are compared to those of a conventional single-line anchor geometry.Multiline anchor net force is calculated by vector summing the contributing tensions of the lines connected to the anchor. Results show that the behavior of the multiline anchor net force is governed by the connected line contributing the largest tension.Mean and maximum anchor forces are decreased in the 3-line anchor system and increased in the 6-line anchor system, relative to the single-line system. The average direction of multiline anchor net force is aligned with environmental load direction, and a wider range of multiline anchor net force directions are exhibited for wavedominated load cases. Direction reversal of the multiline anchor net force under constant wind, wave, and current direction is small and infrequent. These force direction results reveal that a multiline anchor must have axisymmetric strength.
“…The details of the FVW method for wind turbine aerodynamic calculations can be found in Ref. [18] and Ref. [21].…”
Section: Fvw Model and Validationmentioning
confidence: 99%
“…In this study, the free vortex wake (FVW) method [18] is used to analyze the influence of the deflection angle of the flaps on the wind turbine blade aerodynamic load and wake flow field and is described and validated firstly. Subsequently, the aerodynamic performance of the airfoil, with the trailing-edge flap, as well as the influence of the trailing-edge flap on the blade aerodynamic load and the wake flow field, are analyzed in detail.…”
As a result of the large-scale trend of offshore wind turbines, wind shear and turbulent wind conditions cause significant fluctuations of the wind turbine’s torque and thrust, which significantly affect the service life of the wind turbine gearbox and the power output stability. The use of a trailing-edge flap is proposed as a supplement to the pitch control to mitigate the load fluctuations of large-scale offshore wind turbines. A wind turbine rotor model with a trailing-edge flap is established by using the free vortex wake (FVW) model. The effects of the deflection angle of the trailing-edge flap on the load distribution of the blades and wake flow field of the offshore wind turbine are analyzed. The wind turbine load response under the control of the trailing-edge flap is obtained by simulating shear wind and turbulent wind conditions. The results show that a better control effect can be achieved in the high wind speed condition because the average angle of attack of the blade profile is small. The trailing-edge flap significantly changes the load distribution of the blade and the wake field and mitigates the low-frequency torque and thrust fluctuations of the turbine rotor under the action of wind shear and turbulent wind.
“…Challenges and innovative solutions are discussed in three papers of the theme issue: the papers by Sorensen et al [37] and Xu et al [38], which present respectively a CFD method and a free-vortex wake method for aerodynamics, and [39], which proposes an integrated CFD approach to aerodynamics and hydrodynamics.…”
Section: Aerodynamics and Hydrodynamicsmentioning
confidence: 99%
“…Xu et al [38] propose a free-vortex wake method to model the aerodynamics of offshore wind turbines on floating platforms. A three-step and third-order predictor-corrector algorithm is developed to solve a finite difference approximation of the wake governing equation.…”
The design of offshore wind turbines is one of the most fascinating challenges in renewable energy. Meeting the objective of increasing power production with reduced installation and maintenance costs requires a multi-disciplinary approach, bringing together expertise in different fields of engineering. The purpose of this theme issue is to offer a broad perspective on some crucial aspects of offshore wind turbines design, discussing the state of the art and presenting recent theoretical and experimental studies.
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