A twice expansion analysis method in the time-domain for wave action on a floater translating with a large amplitude

Teng, Bin; Jin, Ruijia; Cong, Longfei

doi:10.1016/j.oceaneng.2016.03.033

Cited by 8 publications

(9 citation statements)

References 18 publications

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“…However, due to limited space, the boundary conditions on the free surface and body surface in an IneCS formulation will not be repeated here, as it is not our focus in this paper. We refer interested readers to, for instance, Bai and Teng (2013) and Teng et al (2016), for a comprehensive description of this formulation up to 2nd order.…”

Section: Mathematical Formulationmentioning

confidence: 99%

“…velocity potential and wave elevation, by additional Taylor expansions involving the evaluation of more higher-derivative terms. The second challenge was also partly resolved numerically by Teng et al (2016) to use Stokes theorem to convert the surface-integral of 2nd derivatives of velocity potential into 1st derivatives, with an extra cost of increased order of the derivatives of Green′s function. It is however not clear how the 3rd derivatives of the zeroth-order potential, which according to Shao and Faltinsen (2013) should be present in the 2nd order boundary conditions, can be handled by a similar strategy.…”

Section: Introductionmentioning

confidence: 99%

“…To address the first challenge, Teng et al (2016) were perhaps the first in the literature to extend the IneCS model by Taylor-expanding the boundary conditions around an instantaneous mean position of the structure, with a cost of approximating the free-surface variables at the instantaneous position, for example, velocity potential and wave elevation, by additional Taylor expansions involving the evaluation of more higher-derivative terms. The second challenge was also partly resolved numerically by Teng et al (2016) to use Stokes theorem to convert the surface-integral of second derivatives of velocity potential into first derivatives, with an extra cost of increased order of the derivatives of Green′s function. It is however not clear how the third derivatives of the zeroth-order potential, which according to Shao and Faltinsen (2013) should be present in the second-order boundary conditions, can be handled by a similar strategy.…”

Section: Introductionmentioning

confidence: 99%

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A consistent second‐order hydrodynamic model in the time domain for floating structures with large horizontal motions

Shao

Zheng

Liang

et al. 2021

Computer aided Civil Eng

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Floating offshore structures often exhibit low-frequency oscillatory motions in the horizontal plane, with amplitudes in the same order as their characteristic dimensions and larger than the corresponding wave-frequency responses, making the traditional formulations in an inertial coordinate system inconsistent and less applicable. To address this issue, we explore an alternative formulation completely based on a non-inertial body-fixed coordinate system. Unlike the traditional seakeeping models, this formulation consistently allows for large-amplitude horizontal motions. A numerical model based on a higher-order boundary element is applied to solve the resulting boundary-value problems in the time domain. A new set of explicit time-integration methods, which do not necessitate the use of upwind schemes for spatial derivatives, are designed to deal with the convectivetype free-surface conditions. To suppress the weak saw-tooth instabilities on the free surface in time marching, we also present novel low-pass filters based on optimized weighted-least-squares, which are in principle applicable for both structured and unstructured meshes. For ship seakeeping and added resistance analyses, we show that the present computational model does not need to use softsprings for surge and sway, in contrast to the traditional models. For a spar floating offshore wind turbine (FOWT), the importance of consistently taking into account the effects of large horizontal motions is demonstrated considering the bichromatic incident waves. The present model is also referred to as a complete 2nd order wave-load model, as all the 2nd order wave loads, including the sumfrequency and difference-frequency components, are solved simultaneously.

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Section: Mathematical Formulationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A consistent second‐order hydrodynamic model in the time domain for floating structures with large horizontal motions

Shao

Zheng

Liang

et al. 2021

Computer aided Civil Eng

View full text Add to dashboard Cite

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“…A similar procedure can be followed to approximate other implicit schemes. The results for the 2nd-order Crank-Nicolson scheme is shown in Equation (37), which is used throughout this study.…”

Section: Conflicts Of Interestmentioning

confidence: 99%

“…It also mathematically avoids the inconsistencies that a traditional formulation in an earth-fixed coordinate system has. To overcome the difficulties of the traditional formulation when the expansion parameter is not small, Teng et al [37] proposed a twice-expansion method to study the wave-structure interaction problems, allowing for large horizontal motions of the structures.…”

Section: Introductionmentioning

confidence: 99%

Hydrodynamic Responses of a 6 MW Spar-Type Floating Offshore Wind Turbine in Regular Waves and Uniform Current

Zheng

Chen

Liang

et al. 2020

Fluids

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In order to improve the understanding of hydrodynamic performances of spar-type Floating Offshore Wind Turbines (FOWTs), in particular the effect of wave-current-structure interaction, a moored 6MW spar-type FOWT in regular waves and uniform current is considered. The wind loads are not considered at this stage. We apply the potential-flow theory and perturbation method to solve the weakly-nonlinear problem up to the second order. Unlike the conventional formulations in the inertial frame of reference, which involve higher derivatives on the body surface, the present method based on the perturbation method in the non-inertial body-fixed coordinate system can potentially avoid theoretical inconsistency at sharp edges and associated numerical difficulties. A cubic Boundary Element Method (BEM) is employed to solve the resulting boundary-value problems (BVPs) in the time domain. The convective terms in the free-surface conditions are dealt with using a newly developed conditionally stable explicit scheme, which is an approximation of the implicit Crank–Nicolson scheme. The numerical model is firstly verified against three reference cases, where benchmark results are available, showing excellent agreement. Numerical results are also compared with a recent model test, with a fairly good agreement though differences are witnessed. Drag loads based on Morison’s equation and relative velocities are also applied to quantify the influence of the viscous loads. To account for nonlinear restoring forces from the mooring system, a catenary line model is implemented and coupled with the time-domain hydrodynamic solver. For the considered spar-type FOWT in regular-wave and current conditions, the current has non-negligible effects on the motions at low frequencies, and a strong influence on the mean wave-drift forces. The second-order sum-frequency responses are found to be negligibly small compared with their corresponding linear components. The viscous drag loads do not show a strong influence on the motions responses, while their contribution to the wave-drift forces being notable, which increases with increasing wave steepness.

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An Overview of Structural Design, Analysis and Common Monitoring Technologies for Floating Platform and Flexible Cable and Riser

Zhao

Gou

et al. 2022

China Ocean Eng

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Offshore oil and gas development plays an important part in the global energy sector. Offshore platforms and flexible pipes are the key equipments in the whole offshore oil and gas development system. Because of the randomness and uncertainty of wave and current loads in the ocean environment, the structural design and mechanical analysis of the marine equipment can be highly complicated. Therefore, this paper reviews the recent works of the theoretical model, numerical simulation, and experimental test in three research areas: hydrodynamic analysis of offshore platforms, structural mechanics analysis of flexible pipe and cable, and monitoring technology of offshore floating structures under marine loads. By analyzing their main research methods and key technical difficulties, this paper provides theoretical basis and technical support for the reliability engineering application of offshore platforms and flexible pipelines. Also, China is relatively backward in the design of marine floating platform, the design, analysis and testing of flexible pipeline and cable, as well as the marine equipment prototype monitoring technology research. Calling for breakthroughs at the earliest possible stage in the above fields, prime research should be focused on and strategic planning should be made to deal with “key areas and stranglehold problems”. It is of great significance for the development of China’s deep-sea energy and resource development of independent technology and on time to achieve the “carbon peak” national strategic objectives.

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A twice expansion analysis method in the time-domain for wave action on a floater translating with a large amplitude

Cited by 8 publications

References 18 publications

A consistent second‐order hydrodynamic model in the time domain for floating structures with large horizontal motions

A consistent second‐order hydrodynamic model in the time domain for floating structures with large horizontal motions

Hydrodynamic Responses of a 6 MW Spar-Type Floating Offshore Wind Turbine in Regular Waves and Uniform Current

An Overview of Structural Design, Analysis and Common Monitoring Technologies for Floating Platform and Flexible Cable and Riser

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