Morison wave force coefficients for application to random seas

Burrows, Roger; Tickell, R.G.; Hames, D.; Najafian, G.

doi:10.1016/s0141-1187(97)00023-0

Cited by 31 publications

(6 citation statements)

References 2 publications

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“…This was the inevitable result of the delicate clamping mechanism used to hold the dropper lines in place, and the difficulty to apply vertical pretension, as a toolarge pretension would have resulted in excessive mussel drop-off. Due to that relative horizontal motion of the dropper lines, further enhancement of the evaluation method is required for a more precise estimation of drag coefficients, but more importantly of inertia coefficients, C M [51,52], which will be presented in an upcoming publication. As the relative motion, and thus relative velocity of the fluid field driving the force response is decreased through the elastic behavior of the dropper lines, differences in force coefficients, as well as measured force peaks, are expected; however, the determination of the maximum deflection amplitude was not determined as optical access in the Large Wave Flume and is greatly reduced through suspended sediments.…”

Section: Discussionmentioning

confidence: 99%

Large-Scale Laboratory Experiments on Mussel Dropper Lines in Ocean Surface Waves

Gieschen

Schwartpaul

Landmann

et al. 2020

JMSE

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The rapid growth of marine aquaculture around the world accentuates issues of sustainability and environmental impacts of large-scale farming systems. One potential mitigation strategy is to relocate to more energetic offshore locations. However, research regarding the forces which waves and currents impose on aquaculture structures in such conditions is still scarce. The present study aimed at extending the knowledge related to live blue mussels (Mytilus edulis), cultivated on dropper lines, by unique, large-scale laboratory experiments in the Large Wave Flume of the Coastal Research Center in Hannover, Germany. Nine-months-old live dropper lines and a surrogate of 2.0 m length each are exposed to regular waves with wave heights between 0.2 and 1.0 m and periods between 1.5 and 8.0 s. Force time histories are recorded to investigate the inertia and drag characteristics of live mussel and surrogate dropper lines. The surrogate dropper line was developed from 3D scans of blue mussel dropper lines, using the surface descriptor Abbott–Firestone Curve as quality parameter. Pull-off tests of individual mussels are conducted that reveal maximum attachment strength ranges of 0.48 to 10.55 N for mussels that had medium 3.04 cm length, 1.60 cm height and 1.25 cm width. Mean drag coefficients of CD = 3.9 were found for live blue mussel lines and CD = 3.4 for the surrogate model, for conditions of Keulegan–Carpenter number (KC) 10 to 380, using regular wave tests.

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Section: Discussionmentioning

confidence: 99%

Large-Scale Laboratory Experiments on Mussel Dropper Lines in Ocean Surface Waves

Gieschen

Schwartpaul

Landmann

et al. 2020

JMSE

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“…The function F is given by 4 † We could reproduce Mansard's surface elevation formula (7) (reference 9), but not the formulas for speed and acceleration, equations (13) and (14), which do not seem to revert to the Stokes second-order solution for a single wave.…”

Section: Appendix C: Tma Correctionmentioning

confidence: 96%

Influence of wave modelling on the prediction of fatigue for offshore wind turbines

Veldkamp

Tempel

2004

Wind Energy

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Currently it is standard practice to use Airy linear wave theory combined with Morison's formula for the calculation of fatigue loads for offshore wind turbines. However, offshore wind turbines are typically placed in relatively shallow water depths of 5-25 m where linear wave theory has limited accuracy and where ideally waves generated with the Navier-Stokes approach should be used.This article examines the differences in fatigue for some representative offshore wind turbines that are found if first-order, second-order and fully non-linear waves are used.The offshore wind turbines near Blyth are located in an area where non-linear wave effects are common.Measurements of these waves from the OWTES project are used to compare the different wave models with the real world in spectral form. Some attention is paid to whether the shape of a higher-order wave height spectrum (modified JONSWAP) corresponds to reality for other places in the North Sea, and which values for the drag and inertia coefficients should be used.

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“…Journee and Massie [23] and Sarpkay and Isaacson [24] proposed various methods to define the drag and inertia coefficients for better estimation of the solution to the Morison equation. Burrows et al [25] also defined several techniques, such as least square, cross-spectral, and the methods of moments, to identify these coefficients, and subsequently measured the wave loads using the Morison equation to prove the accuracy of predicting random forces using the equation. The measured data were later shown to sufficiently match the predicted values, which confirmed the suitability of the equation for measuring wave loads.…”

Section: Introductionmentioning

confidence: 99%

Study of Floating Wind Turbine with Modified Tension Leg Platform Placed in Regular Waves

Song

Lim

2019

Energies

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In this study, the typical ocean environment was simulated with the aim to investigate the dynamic response under various environmental conditions of a Tension Leg Platform (TLP) type floating offshore wind turbine system. By applying Froude scaling, a scale model with a scale of 1:200 was designed and model experiments were carried out in a lab-scale wave flume that generated regular periodic waves by means of a piston-type wave generator while a wave absorber dissipated wave energy on the other side of the channel. The model was designed and manufactured based on the standard prototype of the National Renewable Energy Laboratory (NREL) 5 MW offshore wind turbine. In the first half of the study, the motion and structural responses for operational wave conditions of the North Sea near Scotland were considered to investigate the performance of a traditional TLP floating wind turbine compared with that of a newly designed TLP with added mooring lines. The new mooring lines were attached with the objective of increasing the horizontal stiffness of the system and thereby reducing the dominant motion of the TLP platform (i.e., the surge motion). The results of surge translational motions were obtained both in the frequency domain, using the response amplitude operator (RAO), and in the time domain, using the omega arithmetic method for the relative velocity. The results obtained show that our suggested concept improves the stability of the platform and reduces the overall motion of the system in all degrees-of-freedom. Moreover, the modified design was verified to enable operation in extreme wave conditions based on real data for a 100-year return period of the Northern Sea of California. The loads applied by the waves on the structure were also measured experimentally using modified Morison equation—the formula most frequently used to estimate wave-induced forces on offshore floating structures. The corresponding results obtained show that the wave loads applied on the new design TLP had less amplitude than the initial model and confirmed the significant contribution of the mooring lines in improving the performance of the system.

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Morison wave force coefficients for application to random seas

Cited by 31 publications

References 2 publications

Large-Scale Laboratory Experiments on Mussel Dropper Lines in Ocean Surface Waves

Large-Scale Laboratory Experiments on Mussel Dropper Lines in Ocean Surface Waves

Influence of wave modelling on the prediction of fatigue for offshore wind turbines

Study of Floating Wind Turbine with Modified Tension Leg Platform Placed in Regular Waves

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