A numerical investigation of second-order difference-frequency forces and motions of a moored ship in shallow water

You, Jikun; Faltinsen, Odd M.

doi:10.1007/s40722-015-0014-6

Cited by 11 publications

(11 citation statements)

References 11 publications

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“…Shao and Faltinsen [3] used a similar approach to examine the springing phenomenon in ships resulting from sum-frequency excitation with bichromatic waves. You and Faltinsen [4] studied the slowly varying surge motion of a liquefied natural gas carrier model using bichromatic waves in a head sea, and compared the numerical results with experimental data from Marintek. Ohyama and Hsu [5] examined the motion of a rectangular floating body in response to nonlinear bichromatic waves to examine the validity range of a second-order approximation.…”

Section: Introductionmentioning

confidence: 99%

Bichromatic Wave Selection for Validation of the Difference-Frequency Transfer Function for the OC6 Validation Campaign

Tom

Robertson

Jonkman

et al. 2019

ASME 2019 2nd International Offshore Wind Technical Conference

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The focus of the Offshore Code Comparison Collaboration, Continuation, with Correlation and unCertainity (OC6) project, which operates under the International Energy Agency Wind Task 30, is to refine the accuracy of engineering tools used to design offshore wind turbines. In support of this work, a new validation campaign is being developed that seeks to better understand the nonlinear wave loading that excites floating wind systems at their low-frequency, rigid-body modes in surge and pitch. The validation data will be employed in a three-way validation between simplified engineering tools and higher-fidelity tools, such as computational fluid dynamics (CFD). Irregular wave spectrums, which are traditionally used to examine the nonlinear wave interaction with offshore structures, are too computationally expensive to be simulated in CFD tools, and so we will employ bichromatic wave cases instead. This paper reviews the process used to choose the bichromatic wave pairs to be applied in the campaign to validate the second-order difference-frequency quadratic and potential loads at the surge and pitch natural frequencies of a floating semisubmersible.

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Section: Introductionmentioning

confidence: 99%

Bichromatic Wave Selection for Validation of the Difference-Frequency Transfer Function for the OC6 Validation Campaign

Tom

Robertson

Jonkman

et al. 2019

ASME 2019 2nd International Offshore Wind Technical Conference

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“…4 contains a brief summary of the main dimensions and mass properties of the platform. Wave probe in the undisturbed region, longitudinally located at the platform's center of gravity (without the platform present) and transversally located at 4 5 of the width of the computational domain. The wave period is 30s and wave amplitude 1.7m.…”

Section: Resultsmentioning

confidence: 99%

“…3. Surface elevation time history (incident wave): distance of the free surface to the z=0 plane at a point located in the undisturbed region, longitudinally located at the platform's center of gravity and transversally located at 4 5 of the width of the computational domain.…”

Section: Resultsmentioning

confidence: 99%

“…In the calculation of RAOs, monocromatic waves are used in the time domain numerical methods. In practice, wave spectra should be used to capture second difference frequency effects [3][4][5], which can have important effects on the resonance responses in heave and pitch. The choice of using monochro- Example of the output of the analysis process of the motion time histories.…”

Section: Resultsmentioning

confidence: 99%

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Influence of Viscosity and Non-Linearities in Predicting Motions of a Wind Energy Offshore Platform in Regular Waves

Ferrandis

Bonfiglio

Rodríguez

et al. 2020

Journal of Offshore Mechanics and Arctic Engineering

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Motion predictions of floating bodies in extreme waves represent a challenging problem in naval hydrodynamics. The solution of the seakeeping problem involves the study of complex non-linear wave-body interactions that require large computational costs. For this reason, over the years, many seakeeping models have been formulated in order to predict ship motions using simplified flow theories, usually based on potential flow theories. Neglecting viscous effects in the wave-induced forces might largely underestimate the energy dissipated by the system. This problem is particularly relevant for unconventional floating bodies at resonance. In these operating conditions, the linear assumption is no longer valid, and conventional boundary element methods, based on potential flow, might predict unrealistic large responses if not corrected with empirical viscous damping coefficients. The application considered in this study is an offshore platform to be operated in a wind farm requiring operability even in extreme meteorological conditions. In this paper, we compare heave and pitch response amplitude operators predicted for an offshore platform using three different seakeeping models of increasing complexity, namely, a frequency-domain boundary element method (BEM), a partly nonlinear time domain BEM, and a non-linear viscous model based on the solution of the unsteady Reynolds-averaged Navier–Stokes (URANS) equations. Results are critically compared in terms of accuracy, applicability, and computational costs.

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“…In this context, the Boundary Element Method (BEM) has been a popular method to solve the wave-ship interactions. Such models, which are also known as panel models, are applied in both offshore (e.g., Huijsmans et al, 2001;Newman, 2005;Zhao et al, 2011) and coastal waters (e.g., Van Oortmerssen, 1976;You and Faltinsen, 2015;Xiong et al, 2015) to predict the wave impact on floating bodies. More recently, potential flow models based on the Finite Element Method (FEM) have been developed to simulate similar interactions (e.g., Yan and Ma, 2007;Ma and Yan, 2009).…”

Section: Introductionmentioning

confidence: 99%

Simulating waves and their interactions with a restrained ship using a non-hydrostatic wave-flow model

Rijnsdorp

Zijlema

2016

Coastal Engineering

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This paper presents a numerical model to simulate the evolution of waves and their interactions with a restrained ship that is moored in coastal waters. The model aims to be applicable at the scale of a harbour or coastal region, while accounting for the key physical processes that determine the hydrodynamic loads on the ship. Its methodology is based on the non-hydrostatic wave-flow model SWASH, which provides an efficient tool to simulate the nonlinear dynamics that govern the nearshore wave field. In this work, we propose a new numerical algorithm that accounts for the presence of a non-moving floating body, to resolve the wave impact on a restrained ship. The model is validated through comparisons with an analytic solution, a numerical solution, and two laboratory campaigns. The results of the model-data comparison demonstrate that the model captures the scattering of waves by a restrained body. Furthermore, it gives a reasonable prediction of the hydrodynamic loads that act on a restrained container ship for a range of wave conditions. Importantly, the model captures these dynamics efficiently, which demonstrates that it retains this favourable property of the non-hydrostatic approach when a floating body is included. The findings of this study suggest that the model provides a promising new alternative to simulate the nonlinear evolution of waves and their impact on a restrained ship at the scale of a realistic harbour or coastal region.

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A numerical investigation of second-order difference-frequency forces and motions of a moored ship in shallow water

Cited by 11 publications

References 11 publications

Bichromatic Wave Selection for Validation of the Difference-Frequency Transfer Function for the OC6 Validation Campaign

Bichromatic Wave Selection for Validation of the Difference-Frequency Transfer Function for the OC6 Validation Campaign

Influence of Viscosity and Non-Linearities in Predicting Motions of a Wind Energy Offshore Platform in Regular Waves

Simulating waves and their interactions with a restrained ship using a non-hydrostatic wave-flow model

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