A Non-Linear Potential Model to Predict Large-Amplitudes-Motions: Application to the SEAREV Wave Energy Converter

Gilloteaux, Jean‐Christophe; Babarit, Aurélien; Ducrozet, Guillaume; Durand, M.; Cle´ment, Alain H.

doi:10.1115/omae2007-29308

Cited by 27 publications

(42 citation statements)

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“…In this case, the linear model may not be able to accurately represent the actual system dynamics. As a result, time-domain models of WECs are often employed to take these nonlinear characteristics into account (Gilloteaux et al, 2007a;Guerinel et al, 2011). This paper focuses on the time-domain simulations of a specific floating point absorber WEC-the Wavebob.…”

Section: Introductionmentioning

confidence: 99%

Investigation on parametrically excited motions of point absorbers in regular waves

Tarrant

Meskell

2016

Ocean Engineering

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Abstract.Free floating objects such as a self-reacting wave energy converter (WEC), may experience a condition known as parametric resonance. In this situation, at least two degrees of freedom become coupled when the incident wave has a frequency approximately twice the pitch or roll natural frequency. This can result in very large amplitude motion in pitch and/or roll. While classic linear theory has proven sufficient for describing small motions due to small amplitude waves, a point absorber WEC is often designed to operate in resonant conditions, and therefore, exhibits significant nonlinear responses. In this paper, a time-domain nonlinear numerical model is presented for describing the dynamic stability of point absorbers. The pressure of the incident wave is integrated over the instantaneous wetted surface to obtain the nonlinear Froude-Krylov excitation force and the nonlinear hydrostatic restoring forces, while first order diffraction-radiation forces are computed by a linear potential flow formulation. A numerical benchmark study for the simulation of parametric resonance of a specific WEC -the Wavebob -has been implemented and validated against experimental results. The implemented model has shown good accuracy in reproducing both the onset and steady state response of parametric resonance. Limits of stability were numerically computed showing the instability regions in the roll and pitch modes. Investigation on parametrically excited motions of point absorbers in regular wavesKevin Tarrant a , Craig Meskell a, * AbstractFree floating objects such as a self reacting wave energy converter (WEC), may experience a condition known as parametric resonance. In this situation, at least two degrees of freedom become coupled when the incident wave has a frequency approximately twice the pitch or roll natural frequency. This can result in very large amplitude motion in pitch and/or roll. While classic linear theory has proven sufficient for describing small motions due to small amplitude waves, a point absorber WEC is often designed to operate in resonant conditions, and therefore, exhibits significant nonlinear responses. In this paper, a time-domain nonlinear numerical model is presented for describing the dynamic stability of point absorbers. The pressure of the incident wave is integrated over the instantaneous wetted surface to obtain the nonlinear Froude-Krylov excitation force and the nonlinear hydrostatic restoring forces, while first order diffraction-radiation forces are computed by a linear potential flow formulation. A numerical benchmark study for the simulation of parametric resonance of a specific WEC-the Wavebob-has been implemented and validated against experimental results. The implemented model has shown good accuracy in reproducing both the onset and steady state response of parametric resonance. Limits of stability were numerically computed showing the instability regions in the roll and pitch modes.

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Section: Introductionmentioning

confidence: 99%

Investigation on parametrically excited motions of point absorbers in regular waves

Tarrant

Meskell

2016

Ocean Engineering

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“…Bhinder et al (2011) used CFD outputs to identify a parameter value for an additional nonlinear term, representing the viscous forces, to be added to a linear hydrodynamic model. Including the nonlinearity, due to the time varying wetted body surface, into a hydrodynmamic model, has been investigated by integrating the pressure over the instantaneous wetted surface of the body at each time step, to calculate nonlinear Froude-Krylov forces (Gilloteaux et al 2008) (Babarit and LaporteWeywada 2009) (Guérinel et al 2011). Zurkinden et al (2014) included nonlinearity into their hydrodynamic model, by representing the hydrostatic restoring force with a cubic polynomial, identified from experimental data.…”

Section: Introductionmentioning

confidence: 99%

Numerical wave tank identification of nonlinear discrete time hydrodynamic models

Davidson¹,

Giorgi²,

Ringwood³

2015

Renewable Energies Offshore

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Hydrodynamic models are important for the design, simulation and control of wave energy converters (WECs). Linear hydrodynamic models have formed the basis for this and have been well verified and validated over operating conditions for which small amplitude assumptions apply. At larger amplitudes a number of nonlinear effects may appear. One of these effects is due to the changing bouyancy force as the body moves in and out of the water. In this paper we look at identifying a nonlinear static block to be added the linear hydrodynamic model to account for this effect. The parameters for this nonlinear block are identified from WEC experiments simulated in a numerical wave tank (NWT). The parameters for the linear hydrodynamic model are also identified from NWT experiments. Here we explore the use of a discrete time linear hydrodynamic model which is well suited to the identification procedure.

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“…The main advantages of working with this type of formulation is the more straightforward ability to include arbitrary nonlinear dynamics as some perturbation from the linear solution. This may include nonlinear hydrodynamics (see, e.g., [73][74][75][76][77]), nonlinear mechanical dynamics, such as due to a mooring system (see, e.g., [78]) or some arbitrary control input (see, e.g., [14,16]). Giorgi and Ringwood [79] performed an assessment of the relative importance of various nonlinear perturbations within a Cummins-style time-domain model and compared computational expenses.…”

Section: Numerical Modelingmentioning

confidence: 99%

A Survey of WEC Reliability, Survival and Design Practices

Coe

Rij

2017

Energies

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A wave energy converter must be designed to survive and function efficiently, often in highly energetic ocean environments. This represents a challenging engineering problem, comprising systematic failure mode analysis, environmental characterization, modeling, experimental testing, fatigue and extreme response analysis. While, when compared with other ocean systems such as ships and offshore platforms, there is relatively little experience in wave energy converter design, a great deal of recent work has been done within these various areas. This paper summarizes the general stages and workflow for wave energy converter design, relying on supporting articles to provide insight. By surveying published work on wave energy converter survival and design response analyses, this paper seeks to provide the reader with an understanding of the different components of this process and the range of methodologies that can be brought to bear. In this way, the reader is provided with a large set of tools to perform design response analyses on wave energy converters.

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A Non-Linear Potential Model to Predict Large-Amplitudes-Motions: Application to the SEAREV Wave Energy Converter

Cited by 27 publications

References 0 publications

Investigation on parametrically excited motions of point absorbers in regular waves

Investigation on parametrically excited motions of point absorbers in regular waves

Numerical wave tank identification of nonlinear discrete time hydrodynamic models

A Survey of WEC Reliability, Survival and Design Practices

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