Experimental study of collar protection for local scour reduction around offshore wind turbine monopile foundations

Tang, Zihao; Melville, Bruce W.; Shamseldin, Asaad Y.; Guan, Dawei; Singhal, Naresh; Yao, Zishun

doi:10.1016/j.coastaleng.2023.104324

Cited by 20 publications

(9 citation statements)

References 33 publications

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“…In this study, fatigue analyses are performed under 22 environmental states provided by van der Tempel (2006), taking into account both operational and parked conditions. These 22 environmental states are shown in Table 4.…”

Section: Environmental States and Load Casesmentioning

confidence: 99%

“…For example, armouring protection has the disadvantage that the projectile cannot be accurately cast in complex sea conditions and is easy to be washed away (Wang et al, 2023;Zhang et al, 2023). Flow-altering protection has the disadvantages of high cost and changing the dynamic characteristics of the foundation (Tang et al, 2023). As offshore struc-tures, wind turbines are vulnerable to corrosion from seawater, which makes the fatigue problem worse (Amirafshari et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

“…Many researchers have studied the effect of scour on fatigue damage accumulation in OWTs. For instance, van der Tempel (2006) investigated the frequency and fatigue of piles under different scour depths and concluded that scour has little effect on the natural frequencies but a major effect on fatigue damage. Zhang et al (2021) found that scour depth has a significant influence on monopile impedance.…”

Section: Introductionmentioning

confidence: 99%

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Effect of scour on the fatigue life of offshore wind turbines and its prevention through passive structural control

Cao,

Wu,

Yang

et al. 2024

Wind Energ. Sci.

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Abstract. Offshore wind turbine (OWT) support structures are exposed to the risk of fatigue damage and scour, and this risk can be effectively mitigated by installing structural control devices such as tuned mass dampers (TMDs). However, time-varying scour altering OWTs' dynamic characteristics has an impact on the TMD design and fatigue life, which has rarely been studied before. In this paper, a simplified modal model is used to investigate the influence of scour and a TMD on the fatigue life evaluation of a 5 MW OWT's support structure, and a traditional method and a newly developed optimization technique are both presented to obtain TMD parameters. This optimization technique aims at finding optimal parameters of the TMD which maximize the fatigue life of a hotspot at the mudline, and the effect of time-varying scour can be considered. This study assumes that the TMD operates in the fore–aft (FA) direction, while the vibration in the side–side (SS) direction is uncontrolled. Results show that scour can decrease the fatigue life by about 24.1 % and that the TMD can effectively suppress vibration and increase the fatigue life. When the scour depth reaches 1.3 times the pile diameter, the TMD with a mass ratio of 1 % can increase the fatigue life of an OWT's support structure by about 64.6 %. Further, it is found that the fatigue life can be extended by 25 % with the TMD optimized by the proposed optimization technique rather than using a traditional design method which does not take the change in dynamic characteristics into account.

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Section: Environmental States and Load Casesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of scour on the fatigue life of offshore wind turbines and its prevention through passive structural control

Cao,

Wu,

Yang

et al. 2024

Wind Energ. Sci.

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“…Alabi et al [23] conducted a long experiment of about 40 days, and the results showed that collars can not only reduce the equilibrium scour depth but also slow down the scouring process. To increase the protection efficiency of collars, Tang et al [24] proposed a prediction equation for the equilibrium scour depth of a single pile under collar protection and a formula for the protection efficiency.…”

Section: Introductionmentioning

confidence: 99%

Three-Dimensional Turbulent Simulation of Bivariate Normal Distribution Protection Device

Liu,

Li,

Huang

et al. 2024

JMSE

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In response to the deficiencies in existing bridge pier scour protection technologies, this paper introduces a novel protective device, namely a normal distribution-shaped surface (BND) protection devices formed by rotating a concave normal curve. A three-dimensional turbulent SST k − ω model is constructed, and physical model experiments of conical surfaces are conducted to validate the mathematical model. The simulation analyzes longitudinal water flow, downflow, vorticity intensity, and shear stress within normal and conical surfaces. The results show that the downflow distribution in front of the pier spans a relative water depth of (−0.45, 0.67), with a peak velocity approximately 70% of the longitudinal flow velocity. Circulation forms within the surfaces, with the main vortex flux inside the BND being 33% lower than that inside the conical surface. The maximum shear stress coefficient inside the BND can reach 9, and the protective surface isolates the bed from the flow to prevent scouring by high shear stress. The velocity gradient at the edge of the surface is small, and the edge shear stress of the 3D normal distribution-shaped surface (BND) protection device is only one-third of that of the conical surface, preventing edge scouring. The large shear stress and its distribution area decrease monotonically with the increase in surface width. When the surface width is four times the diameter, the distribution range of the shear stress coefficient greater than 1 is very small. The study of three-Dimensional turbulence within the BND provides a numerical basis for an anti-scour design.

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“…The spoiler mainly affects the direction of water flow to divert it in front of the pile, and its protective effect is affected by the angle of the top corner [28].As for the spoiler structure set in the pile foundation part, we can refer to the scour protection of bridge abutment and consider adopting the simple structure of circular type scour guard ring [29,30]. After the flume test and numerical model simulation studies, it can be determined that a more obvious effect of scour prevention can be discerned [31]. On the basis of the circular type, there are also other forms with more complicated shapes and structures, such as by changing the circular shape into a wing-type washer guard ring [32]; or increasing the thickness of the guard ring to form a neck ring [33] and changing the outer diameter of the guard ring on the basis of the neck ring to form a narrower flare at the top and a wider flare at the bottom [34].…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of Local Scour Protection around the Foundation of an Offshore Wind Turbine

Zhang,

Yu,

Yin

et al. 2024

JMSE

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The pile foundations of offshore wind turbines face serious problems from scour damage. This study takes offshore wind turbine monopile foundations as the research object and proposes an innovative anti-scour device for the protection net. A numerical simulation research method based on CFD-DEM was used to model the local scour of the pile foundation and protection net. The validity of the numerical model was verified by comparing the simulation results of the local scour of the pile foundation under the condition of clear water scour and the results of the flume test. The permeability rate was defined to characterize the overwatering of the protection net, and numerical simulations were performed for protection nets with permeability in the range of 0.681 to 0.802. The flow field perturbations, changes in washout pit morphology, and changes in washout depth development due to the protective netting were also analyzed. It was found that the protection net can effectively reduce the flow velocity around the pile, cut down the intensity of the submerged water in front of the pile, and provide scouring protection. Finally, the analysis and summary of the protection efficiency of the different protection nets revealed that the protection efficiency within the nets was consistently the highest. On the outside of the net, the protection efficiency is poor at a small permeability rate but increases with an increasing permeability rate.

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Experimental study of collar protection for local scour reduction around offshore wind turbine monopile foundations

Cited by 20 publications

References 33 publications

Effect of scour on the fatigue life of offshore wind turbines and its prevention through passive structural control

Effect of scour on the fatigue life of offshore wind turbines and its prevention through passive structural control

Three-Dimensional Turbulent Simulation of Bivariate Normal Distribution Protection Device

Numerical Investigation of Local Scour Protection around the Foundation of an Offshore Wind Turbine

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