The Impact of Unsteadiness on the Aerodynamic Loads of a Floating Offshore Wind Turbine

Schulz, Christian W.; Özinan, Umut; Netzband, Stefan; Cheng, Po Wen; Abdel-Maksoud, Moustafa

doi:10.1088/1742-6596/2626/1/012064

Cited by 3 publications

(3 citation statements)

References 22 publications

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“…Regarding the two different motion to inflow velocity ratios tested, it seems that the chosen b vel has negligible influence on the occurrence of the transient aerodynamic behaviour, because nearly no difference between the corresponding curves is present. This is in line with the conclusions drawn from similar simulations of the FLOATGEN wind turbine using a panel method and a BEMT method (Schulz et al, 2023).…”

Section: Simulation Of Extended Motion Parameterssupporting

confidence: 90%

“…In practise, the investigated pure surge motion is superposed with a rotor speed oscillation in below rated conditions. The rotor speed oscillation has shown to trigger a strong dynamic inflow effect even at low motion frequencies in a previous work (Schulz et al, 2023). However, the observed phenomena will most likely also occur, when a concurrent rotor speed variation is present.…”

Section: Occurrence In Full Scalementioning

confidence: 70%

“…In a recent work of the authors (Schulz et al, 2023), a small contribution of transient aerodynamic phenomena to the torque and thrust response of the Vestas V80 rotor to surge motions was identified. While the unsteady airfoil correction of a BEMT method predicted a decrease of the load amplitudes due to the unsteady airfoil effect at high motion frequencies, panel method simulations showed a slight increase.…”

Section: Numerical Investigationsmentioning

confidence: 98%

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Wind turbine rotors in surge motion: New insights into unsteady aerodynamics of FOWT from experiments and simulations

Schulz,

Netzband,

Özinan

et al. 2023

Preprint

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Abstract. An accurate prediction of the unsteady loads acting on floating offshore wind turbines (FOWT) under consideration of wave excitation is crucial for a resource-efficient turbine design. Despite a considerable number of simulation studies in this area, it is still not fully understood, which unsteady aerodynamic phenomena have a notable influence on the loads acting on a wind turbine rotor in motion. In the present study, investigations are carried out to evaluate of the most relevant unsteady aerodynamic phenomena for a wind turbine rotor in surge motion. As a result, inflow conditions are determined for which a significant influence of these phenomena on the rotor loads can be expected. The experimental and numerical investigations are conducted on a two-bladed wind turbine rotor subjected to a tower top surge motion. A specialised wind tunnel test rig has been developed to measure the aerodynamic torque response of the rotor subjected to surge motions with moderate frequencies. The torque measurements are compared to two free vortex wake methods, namely a panel and a lifting-line method. Unsteady contributions that cannot be captured using quasi-steady modelling have not been detected in either the measurements or the simulations in the covered region of motion frequencies. The surge motion frequencies were limited to a moderate range due to vibrations occurring in the experiments. Therefore, a numerical study with an extended the range of motion frequencies using the panel and the lifting-line method was performed. The results reveal significant unsteady contributions of the surge motions to the torque and thrust response that cannot be modelled in a quasi-steady way. Furthermore, the results show the presence of the returning wake effect, which is known from helicopter aerodynamics. Additional simulations of the UNAFLOW scale model and the IEA 15 MW rotor demonstrate that the occurrence of the returning wake effect is independent from the turbine, but determined by the ratio of rotor speed and surge motion. In case of the IEA 15 MW, a notable impact of the returning wake effect was found at surge motion frequencies in the range of typical wave periods. Finally, a comparison with OpenFAST simulations reveals notable differences in the modelling of the unsteady aerodynamic behaviour in comparison to a FVW method.

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Section: Simulation Of Extended Motion Parameterssupporting

confidence: 90%

Section: Occurrence In Full Scalementioning

confidence: 70%

Section: Numerical Investigationsmentioning

confidence: 98%

See 1 more Smart Citation

Wind turbine rotors in surge motion: New insights into unsteady aerodynamics of FOWT from experiments and simulations

Schulz,

Netzband,

Özinan

et al. 2023

Preprint

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Near-wake measurements and simulations of a floating wind turbine using a four-beam nacelle-based lidar

Özinan,

Gräfe,

Schulz

et al. 2024

J. Phys.: Conf. Ser.

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Recent advances in lidar technology have expanded the possibilities for measuring full-scale wind turbine wakes within the atmospheric boundary layer. This study utilizes a four-beam pulsed lidar installed on the nacelle of a floating turbine to measure the near-wake. The wake measurement campaign was conducted on the Floatgen, with lidar measurements reaching up to 2.5 times the rotor diameter distance. These measurements are presented as 10-minute average radial wind speeds. The focus of this study is on the below rated wind speed of 7 m/s. Free flow conditions were assumed at the farthest measurement points, which are located ±0.9 times the rotor diameter from to the rotor center. The sensitivity of lidar measurements to turbulence intensity, vertical wind shear, and significant wave height was investigated. The environmental conditions were categorized into five cases, considering turbulence, vertical shear, and yaw misalignment as well as waves. Two simulation models with different fidelity levels are used to simulate these cases, and the beam-wise radial wind speed predictions are compared with the measurements. A maximum mean absolute error of 11.3% between the measurements and simulations is observed.

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Wind turbine rotors in surge motion: new insights into unsteady aerodynamics of floating offshore wind turbines (FOWTs) from experiments and simulations

Schulz,

Netzband,

Özinan

et al. 2024

Wind Energ. Sci.

View full text Add to dashboard Cite

Abstract. An accurate prediction of the unsteady loads acting on floating offshore wind turbines (FOWTs) under consideration of wave excitation is crucial for a resource-efficient turbine design. Despite a considerable number of simulation studies in this area, it is still not fully understood which unsteady aerodynamic phenomena have a notable influence on the loads acting on a wind turbine rotor in motion. In the present study, investigations are carried out to evaluate the most relevant unsteady aerodynamic phenomena for a wind turbine rotor in surge motion. As a result, inflow conditions are determined for which a significant influence of these phenomena on the rotor loads can be expected. The experimental and numerical investigations are conducted on a two-bladed wind turbine rotor subjected to a tower-top surge motion. A specialised wind tunnel test rig has been developed to measure the aerodynamic torque response of the rotor subjected to surge motions with moderate frequencies. The torque measurements are compared to two free-vortex-wake (FVW) methods, namely a panel method and a lifting-line method. Unsteady contributions that cannot be captured using quasi-steady modelling have not been detected in either the measurements or the simulations in the covered region of motions ranging from a rotor reduced frequency of 0.55 to 1.09 and with motion velocity amplitudes of up to 9 % of the wind speed. The surge motion frequencies were limited to a moderate range (5 to 10 Hz) due to vibrations occurring in the experiments. Therefore, a numerical study with an extended range of motion frequencies using the panel and the lifting-line method was performed. The results from both FVW methods reveal significant unsteady contributions of the surge motions to the torque and thrust response that have not been reported in the recent literature. Furthermore, the results show the presence of the returning wake effect, which is known from helicopter aerodynamics. Additional simulations of the UNAFLOW scale model and the IEA 15 MW rotor demonstrate that the occurrence of the returning wake effect is independent from the turbine but determined by the ratio of 3P and surge motion frequency. In the case of the IEA 15 MW rotor, a notable impact of the returning wake effect was found at surge motion frequencies in the range of typical wave periods. Finally, a comparison with OpenFAST simulations reveals notable differences in the modelling of the unsteady aerodynamic behaviour in comparison to the FVW methods.

show abstract

The Impact of Unsteadiness on the Aerodynamic Loads of a Floating Offshore Wind Turbine

Cited by 3 publications

References 22 publications

Wind turbine rotors in surge motion: New insights into unsteady aerodynamics of FOWT from experiments and simulations

Wind turbine rotors in surge motion: New insights into unsteady aerodynamics of FOWT from experiments and simulations

Near-wake measurements and simulations of a floating wind turbine using a four-beam nacelle-based lidar

Wind turbine rotors in surge motion: new insights into unsteady aerodynamics of floating offshore wind turbines (FOWTs) from experiments and simulations

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