Recent Developments in the Analysis of Wave Drift Forces, Low-Frequency Damping and Response

Standing, R G; Brendling, W J; Wilson, David C.

doi:10.4043/5456-ms

Cited by 15 publications

(13 citation statements)

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“…Although this formulation is computationally very efficient, its disadvantage is that it contains unphysical high frequencies, which need to be filtered. An improved formulation was proposed by [81] with the product of two sums as F (2)…”

Section: Second-order Slow-drift Force Modelmentioning

confidence: 99%

Multibody modeling for concept-level floating offshore wind turbine design

Lemmer

Luhmann³

et al. 2020

Multibody Syst Dyn

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Existing Floating Offshore Wind Turbine (FOWT) platforms are usually designed using static or rigid-body models for the concept stage and, subsequently, sophisticated integrated aero-hydro-servo-elastic models, applicable for design certification. For the new technology of FOWTs, a comprehensive understanding of the system dynamics at the concept phase is crucial to save costs in later design phases. This requires low-and medium-fidelity models. The proposed modeling approach aims at representing no more than the relevant physical effects for the system dynamics. It consists, in its core, of a flexible multibody system. The applied Newton-Euler algorithm is independent of the multibody layout and avoids constraint equations. From the nonlinear model a linearized counterpart is derived. First, to be used for controller design and second, for an efficient calculation of the response to stochastic load spectra in the frequency-domain. From these spectra the fatigue damage is calculated with Dirlik's method and short-term extremes by assuming a normal distribution of the response. The set of degrees of freedom is reduced, with a response calculated only in the two-dimensional plane, in which the aligned wind and wave forces act. The aerodynamic model is a quasistatic actuator disk model. The hydrodynamic model includes a simplified radiation model, based on potential flow-derived added mass coefficients and nodal viscous drag coefficients with an approximate representation of the second-order slow-drift forces. The verification through a comparison of the nonlinear and the linearized model against a higher-fidelity model and experiments shows that even with the simplifications, the system response magnitude at the system eigenfrequencies and the forced response magnitude to wind and wave forces can be well predicted. One-hour simulations complete in about 25 seconds and even less in the case of the frequency-domain model. Hence, large sensitivity studies and even multidisciplinary optimizations for systems engineering approaches are possible.

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Section: Second-order Slow-drift Force Modelmentioning

confidence: 99%

Multibody modeling for concept-level floating offshore wind turbine design

Lemmer

Luhmann³

et al. 2020

Multibody Syst Dyn

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“…The low frequency surge wave drift damping values used are the full 3D ARG values. The computed statistics of motion mean and the motion rms value are compared with the earlier one degree of freedom motion based predictions in Table ( 5). It follows from this that the difference in predicted variances are small for significant wave heights less than 11.…”

Section: Figures 3 and 4 Present The Extreme Surge Displacementmentioning

confidence: 97%

“…The 3D theoretical wave' drift damping is based upon the near field Added Resistance Gradient (ARG) method developed by Hearn and"Tong (3,19) The 3D simplified theoretical wave drift damping is calculated from the frequency gradient of the wave drift forces, as described by Standing et a1 (5) and further investigated by Hearn and Tong (7).…”

Section: Abalysis Of a K)()jle]) Taber Aim A Kxmed Bakgementioning

confidence: 99%

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Wave Drift Damping Influences Upon The Time Domain Simulations Of Moored Structures

Hearn

Lau

Tong

1988

Offshore Technology Conference

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This paper is concerned with the effects of wave drift damping upon the motions of a moored tanker and a moored offshore barge. The assignment of wave drift damping coefficients, whether predicted or measured. has a significant effect upon the excursions of the moored structure and hence upon the associated line tensions experienced by the mooring system.Procedures for simulating the random sea and determining the Quadratic Transfer Functions of second order wave effects are discussed in the context of including such effects in the time domain simulation of a moored vessel.

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“…(1) modifies to include a linear damping term, B(u), the wave-drift damping. [5] suggested an approximation, referred to as the drift force gradient method, equating the wave-drift damping to the wavenumber times the drift force derivative with respect to radial frequency. [6], taking an heuristic approach, modified this formula with the addition of a second term proportional to the drift force F d itself.…”

Section: Surge and Dampingmentioning

confidence: 99%

Measurements of the slow drift dynamics of a model Pelamis wave energy converter

Retzler

2006

Renewable Energy

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Recent Developments in the Analysis of Wave Drift Forces, Low-Frequency Damping and Response

Cited by 15 publications

References 0 publications

Multibody modeling for concept-level floating offshore wind turbine design

Multibody modeling for concept-level floating offshore wind turbine design

Wave Drift Damping Influences Upon The Time Domain Simulations Of Moored Structures

Measurements of the slow drift dynamics of a model Pelamis wave energy converter

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