The dynamic response of wind turbines operating in a wake flow

Hassan, U.; Taylor, Graham; Garrad, A.D.

doi:10.1016/0167-6105(88)90028-1

Cited by 17 publications

(7 citation statements)

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“…In addition to analyzing various wake measurements, Taylor shows that in waked operations, the root-mean-square (RMS) bending moment of the downwind turbine spaced 5 rotor diameters from the upwind one can increase by 70%. Further analyses of loads data from the Nibe turbines are presented by Hassan et al [14] In this work, we numerically simulated the atmospheric boundary layer over flat terrain under various stability conditions and with different surface aerodynamic roughness heights using large-eddy simulation (LES). We then placed two actuator line turbine models [15] coupled with the National Renewable Energy Laboratory's (NREL) Fatigue, Aerodynamics, Structures, and Turbulence (FAST) turbine system and structural dynamics model [16] into these atmospheric boundary layers and examine their performance and structural response.…”

Section: Introductionmentioning

confidence: 98%

A numerical study of the effects of atmospheric and wake turbulence on wind turbine dynamics

Churchfield

Lee

Michalakes

et al. 2012

Journal of Turbulence

457

409

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Although the atmospheric sciences community has been studying the effects of atmospheric stability and surface roughness on the planetary boundary layer for some time, their effects on wind turbine dynamics have not been well studied. In this study, we performed numerical experiments to explore some of the effects of atmospheric stability and surface roughness on wind turbine dynamics. We used large-eddy simulation to create atmospheric winds and compute the wind turbine flows, and we modeled the wind turbines as revolving and flexible actuator lines coupled to a wind turbine structural and system dynamic model. We examined the structural moments about the wind turbine blade, low-speed shaft, and nacelle; power production; and wake evolution when large 5-MW turbines are subjected to winds generated from low-and high-surface roughness levels representative of offshore and onshore conditions, respectively, and also neutral and unstable atmospheric conditions. In addition, we placed a second turbine 7 rotor diameters downwind of the first one so that we could explore wake effects under these different conditions. The results show that the turbulent structures generated within the atmospheric boundary layer wind simulations cause isolated loading events at least as significant as when a turbine is waked by an upwind turbine. The root-mean-square (RMS) turbine loads are consistently larger when the surface roughness is higher. The RMS blade-root out-of-plane bending moment and low-speed shaft torque are higher when the atmospheric boundary layer is unstable as compared with when it is neutral. However, the RMS yaw moments are either equal or reduced in the unstable case as compared with the neutral case. For a given surface roughness, the ratio of power produced by the downwind turbine relative to that of the upwind turbine is 15-20% higher when the conditions are unstable as compared with neutral. For a given atmospheric stability, this power ratio is 10% higher with the onshore roughness value versus the offshore one. The main conclusion is that various coherent turbulent structures that form under different levels of atmospheric stability and surface roughness have important effects on wind turbine structural response, power production, and wake evolution.

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Section: Introductionmentioning

confidence: 98%

A numerical study of the effects of atmospheric and wake turbulence on wind turbine dynamics

Churchfield

Lee

Michalakes

et al. 2012

Journal of Turbulence

457

409

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“…It was clearly explained that the saline environment has great effect in lower cyclic load frequency (Thompson, 1984). Hassan et al (1988) have explained the importance of dynamic loading effects of the wind turbine operations. The location of the wind turbines in a close cluster causes the formation of the wake, which causes the increase in the aerodynamic loads.…”

Section: Effect Of Frequency On Fatigue Crack Growthmentioning

confidence: 99%

“…Table 1. Fatigue damage rates with and without wake effects (Hassan et al, 1988 The increased turbulence intensity causes an increase in wind shear gradients. The intermediate pacing shall be taken into consideration for reducing the turbulence intensity.…”

Section: Effect Of Frequency On Fatigue Crack Growthmentioning

confidence: 99%

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A review on fatigue damages in the wind turbines: Challenges in determining and reducing fatigue failures in wind turbine blades

Subbiah

Ranganathan

et al. 2019

Wind Engineering

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The wind energy has been recognised as one of the rising sustainable energies in the world. The wind turbines are subjected to high aerodynamic loads and they cause vibrations due to the wake formation. The magnitude of the applied loads has significant effects on the crack propagation. The fatigue loads have been identified as one of the key sources of damage, with delamination as the main cause for the failure of the turbine blades. The article presents a review of fatigue damages that have been experienced in the wind turbine blades, and factors that are influenced due to the fatigue loads are discussed. The causes and effects of the fatigue loads have been highlighted, and the ways for preventing the fatigue damage by improving the design lifetime are mainly concentrated in review. The overall review gives an idea for determining and reducing the crack growth in wind turbine blades.

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“…It should be noted that a wind turbine wake generates additional gradients in high-frequency turbulence and wind shear whose resultant unsteady aerodynamic loads might increase the rate of fatigue failure. (Hassan et al, 1988) Furthermore, floating wind turbines, are more susceptible to resonance due to excitations induced by wind-wave and turbulence, unsteady ocean waves and currents, which increase the risk of mechanical and fatigue failure (Liu et al, 2018). Therefore, today, fatigue load alleviation is a focus of intense research activity (Bernhammer et al, 2016).…”

Section: Introductionmentioning

confidence: 99%