Damping estimation, response prediction and fatigue calculation of an operational single pile platform

Cook, Michael F.

doi:10.1575/1912/2760

Cited by 4 publications

(5 citation statements)

References 3 publications

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“…The estimation by the half power bandwidth Figures 1 and 2 show only some of our results, many other examples from our simulations and measurements support these conclusions, e.g. analyses of the random vibrations of a single production platform in the Gulf of Mexico [8].…”

Section: Discussionmentioning

confidence: 49%

“…Vandiver and Campbell used both simulated and measured data to study the MEM's performance on dynamic random vibrations. The results in refs [7,8] reveal that the bias and the variance of the conventional damping estimator are strongly related to the properties of the spectral estimators. They also show that conventional damping estimation is not efficient for short length and noisy measurements.…”

Section: Introductionmentioning

confidence: 99%

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Damping ratio estimation using hybrid methods

Liou

Shen

1990

Mechanical Systems and Signal Processing

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Section: Discussionmentioning

confidence: 49%

Section: Introductionmentioning

confidence: 99%

Damping ratio estimation using hybrid methods

Liou

Shen

1990

Mechanical Systems and Signal Processing

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“…18 Figure 16 shows the water wave making in the test, with states 1 to 6 corresponding to the process from generation to radiation of the water wave. For a single pile structure (typical cylinder), Chen and Duffour followed the published literature and rearranged the expressions of the two damping sources 58 : the simplified viscous damping ratio 𝜁 Hydro,Vis can be derived based on Morison's equation, 59 while the radiation damping ratio 𝜁 Hydro,Rad can be derived based on linear potential flow theory. 60 The total hydrodynamic damping ratio 𝜁 Hydro is the sum of 𝜁 Hydro,Vis and 𝜁 Hydro,Rad .…”

Section: Hydrodynamic Damping Effect In Frequency Domainmentioning

confidence: 99%

Seismic responses and vibration control of offshore wind turbines considering hydrodynamic effects based on underwater shaking table tests

He,

Pan

2023

Earthq Engng Struct Dyn

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The recent construction of numerous offshore wind turbines (OWTs) in seismically active areas worldwide has stimulated research on seismic evaluation and vibration control design for OWTs. Unlike the onshore counterparts, the hydrodynamic effects on the seismic responses of OWTs need to be studied. Besides, the equipment in the nacelle of an OWT is highly sensitive to acceleration. Significant dynamic amplification on the nacelle under horizontal earthquake excitation can cause the malfunction of power generation and even seriously threaten the safety of OWTs. As a promising solution, tuned mass dampers (TMDs) based on the first mode of OWTs need to be tested by various earthquake excitations. In this paper, the seismic amplification effect, the hydrodynamic effects, and the vibration control by a single TMD are investigated through a series of underwater shaking table tests based on a 1:20 scaled model of a 5 MW OWT. The “no water”, “with water”, and “with water and TMD” tests are evaluated and compared. The accelerations of OWTs can be amplified or reduced by the hydrodynamic effects, depending on the natural frequencies and vibration modes of the OWT and the frequency spectrum of the seismic excitation. The earthquake‐induced hydrodynamic damping ratio and hydrodynamic added mass are carefully measured. For the TMD's effect, the single TMD performs reasonably well in seismic vibration control in most cases. Finally, the interaction between hydrodynamic effects and TMD's effect is discussed, and the hydrodynamic damping effect is suggested to be ignored when designing TMDs for OWTs.

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“…The viscous drag term in Morison's equation varies along the immersed cylinder as a result of the nonuniform distribution of vibration accelerations and velocities. Following Cook and after rearranging, the damping ratio for a single pile subjected to viscous drag can be written as:

ζ_{italicHydro, italicVis} = \frac{\int_{- h}^{0} \frac{1}{2} ρ_{w} D C_{d} \sqrt{\frac{8}{π}} σ_{r} ((), z) Φ^{2} ((), z) italicdz}{2 \overset{m}{true} ω_{n}},

where σ r ( z ) is the root mean square of the relative speed between the water wave particle and the pile (and other notation was defined in Section 3.2). For large OWTs, the velocity of the pile can be estimated by

\frac{2 π \overset{x}{true}}{T} ~

0.1 m/second.…”

Section: Hydrodynamic Dampingmentioning

confidence: 99%

Modelling damping sources in monopile‐supported offshore wind turbines

Chen

Duffour

2018

Wind Energy

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Vibration damping in offshore wind turbines is a key parameter to predict reliably the dynamic response and fatigue life of these systems. Damping in an offshore wind turbine originates from different sources, mainly, aerodynamic, structural, hydrodynamic, and soil dampings. The difficulties in identifying the individual contribution from each damping source have led to considerable uncertainty and variation in the values recommended. This paper proposes simplified but direct modelling approaches to quantify the damping contributions from the aerodynamic, hydrodynamic, and soil interactions. Results from these models were systemically compared to published values and when appropriate with simulation results from the software package FAST.The range of values obtained for aerodynamic damping confirmed those available in the literature, and blade element modelling theory was shown to provide good results relatively efficiently. The influence of couplings between fore-aft and side-side directions on the aerodynamic damping contribution was highlighted. The modelling of hydrodynamic damping showed that this damping is much smaller than usually recommended and could be safely ignored for offshore wind turbines. Soil damping strongly depends on the soil specific nonlinear behaviour.

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Damping estimation, response prediction and fatigue calculation of an operational single pile platform

Cited by 4 publications

References 3 publications

Damping ratio estimation using hybrid methods

Damping ratio estimation using hybrid methods

Seismic responses and vibration control of offshore wind turbines considering hydrodynamic effects based on underwater shaking table tests

Modelling damping sources in monopile‐supported offshore wind turbines

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