Global motion and airgap computations for semi-submersible floating production unit in waves

Xinshu Zhang, Xingyu Song, Zhiming Yuan, Yunxiang You

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

We study the global hydrodynamic performance of a semi-submersible floating platform unit in order to optimize the hull form in the future. The hydrodynamic problem is solved by employing potential flow theory and Morison equation for modelling of the viscous effects. The added mass and damping coefficients, as well as the first-order motion responses, second-order mean drift forces, diffracted and radiated wave field, and airgap are computed to examine the hydrodynamic behavior of the floating production unit. The computational results show that the motion responses in short-crested waves are mostly smaller than those in long-crested waves. The maximum wave elevation occurs at WP45 in 45°45° wave heading in long-crested waves. In addition, the minimum airgap occurs at AG45 in 45°45° wave heading in linear waves, while the worst airgap point in nonlinear waves is AG0 in 0°0° wave heading.

Extensive parametric studies have been performed to examine the dependence of the motion responses and the other key design criteria on the principal dimensions including hull draft, column width, column spacing, column corner radius, pontoon height, pontoon width, and the size of cakepiece. By comprehensive and systematic hydrodynamic computations and analyses, it is revealed that the combined vertical motion at the worst airgap location is almost in phase with the wave elevation in extreme wave condition with a peak wave period around 14–15 s. Moreover, it is found that the most efficient way to reduce the motion is to increase the hull draft, though the airgap may also decrease. Besides, reducing the pontoon height can achieve better motion performance and larger airgap simultaneously. This paper aims to provide a benchmark for future studies on automatic hull form optimization.
LanguageEnglish
Pages176-204
Number of pages29
JournalOcean Engineering
Volume141
Early online date20 Jun 2017
DOIs
Publication statusPublished - 1 Sep 2017

Fingerprint

Pontoons
Hydrodynamics
Potential flow
Damping

Keywords

  • semi-submersible FPU
  • global motion responses
  • Airgap
  • wave elevation
  • heave motion
  • parametric study

Cite this

Zhang, Xinshu ; Song, Xingyu ; Yuan, Zhiming ; You, Yunxiang. / Global motion and airgap computations for semi-submersible floating production unit in waves. In: Ocean Engineering. 2017 ; Vol. 141. pp. 176-204.
@article{41a9b30498694a20b7fad2500d1217f9,
title = "Global motion and airgap computations for semi-submersible floating production unit in waves",
abstract = "We study the global hydrodynamic performance of a semi-submersible floating platform unit in order to optimize the hull form in the future. The hydrodynamic problem is solved by employing potential flow theory and Morison equation for modelling of the viscous effects. The added mass and damping coefficients, as well as the first-order motion responses, second-order mean drift forces, diffracted and radiated wave field, and airgap are computed to examine the hydrodynamic behavior of the floating production unit. The computational results show that the motion responses in short-crested waves are mostly smaller than those in long-crested waves. The maximum wave elevation occurs at WP45 in 45°45° wave heading in long-crested waves. In addition, the minimum airgap occurs at AG45 in 45°45° wave heading in linear waves, while the worst airgap point in nonlinear waves is AG0 in 0°0° wave heading.Extensive parametric studies have been performed to examine the dependence of the motion responses and the other key design criteria on the principal dimensions including hull draft, column width, column spacing, column corner radius, pontoon height, pontoon width, and the size of cakepiece. By comprehensive and systematic hydrodynamic computations and analyses, it is revealed that the combined vertical motion at the worst airgap location is almost in phase with the wave elevation in extreme wave condition with a peak wave period around 14–15 s. Moreover, it is found that the most efficient way to reduce the motion is to increase the hull draft, though the airgap may also decrease. Besides, reducing the pontoon height can achieve better motion performance and larger airgap simultaneously. This paper aims to provide a benchmark for future studies on automatic hull form optimization.",
keywords = "semi-submersible FPU, global motion responses, Airgap, wave elevation, heave motion, parametric study",
author = "Xinshu Zhang and Xingyu Song and Zhiming Yuan and Yunxiang You",
year = "2017",
month = "9",
day = "1",
doi = "10.1016/j.oceaneng.2017.06.004",
language = "English",
volume = "141",
pages = "176--204",
journal = "Ocean Engineering",
issn = "0029-8018",
publisher = "Elsevier",

}

Global motion and airgap computations for semi-submersible floating production unit in waves. / Zhang, Xinshu; Song, Xingyu; Yuan, Zhiming; You, Yunxiang.

In: Ocean Engineering, Vol. 141, 01.09.2017, p. 176-204.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Global motion and airgap computations for semi-submersible floating production unit in waves

AU - Zhang, Xinshu

AU - Song, Xingyu

AU - Yuan, Zhiming

AU - You, Yunxiang

PY - 2017/9/1

Y1 - 2017/9/1

N2 - We study the global hydrodynamic performance of a semi-submersible floating platform unit in order to optimize the hull form in the future. The hydrodynamic problem is solved by employing potential flow theory and Morison equation for modelling of the viscous effects. The added mass and damping coefficients, as well as the first-order motion responses, second-order mean drift forces, diffracted and radiated wave field, and airgap are computed to examine the hydrodynamic behavior of the floating production unit. The computational results show that the motion responses in short-crested waves are mostly smaller than those in long-crested waves. The maximum wave elevation occurs at WP45 in 45°45° wave heading in long-crested waves. In addition, the minimum airgap occurs at AG45 in 45°45° wave heading in linear waves, while the worst airgap point in nonlinear waves is AG0 in 0°0° wave heading.Extensive parametric studies have been performed to examine the dependence of the motion responses and the other key design criteria on the principal dimensions including hull draft, column width, column spacing, column corner radius, pontoon height, pontoon width, and the size of cakepiece. By comprehensive and systematic hydrodynamic computations and analyses, it is revealed that the combined vertical motion at the worst airgap location is almost in phase with the wave elevation in extreme wave condition with a peak wave period around 14–15 s. Moreover, it is found that the most efficient way to reduce the motion is to increase the hull draft, though the airgap may also decrease. Besides, reducing the pontoon height can achieve better motion performance and larger airgap simultaneously. This paper aims to provide a benchmark for future studies on automatic hull form optimization.

AB - We study the global hydrodynamic performance of a semi-submersible floating platform unit in order to optimize the hull form in the future. The hydrodynamic problem is solved by employing potential flow theory and Morison equation for modelling of the viscous effects. The added mass and damping coefficients, as well as the first-order motion responses, second-order mean drift forces, diffracted and radiated wave field, and airgap are computed to examine the hydrodynamic behavior of the floating production unit. The computational results show that the motion responses in short-crested waves are mostly smaller than those in long-crested waves. The maximum wave elevation occurs at WP45 in 45°45° wave heading in long-crested waves. In addition, the minimum airgap occurs at AG45 in 45°45° wave heading in linear waves, while the worst airgap point in nonlinear waves is AG0 in 0°0° wave heading.Extensive parametric studies have been performed to examine the dependence of the motion responses and the other key design criteria on the principal dimensions including hull draft, column width, column spacing, column corner radius, pontoon height, pontoon width, and the size of cakepiece. By comprehensive and systematic hydrodynamic computations and analyses, it is revealed that the combined vertical motion at the worst airgap location is almost in phase with the wave elevation in extreme wave condition with a peak wave period around 14–15 s. Moreover, it is found that the most efficient way to reduce the motion is to increase the hull draft, though the airgap may also decrease. Besides, reducing the pontoon height can achieve better motion performance and larger airgap simultaneously. This paper aims to provide a benchmark for future studies on automatic hull form optimization.

KW - semi-submersible FPU

KW - global motion responses

KW - Airgap

KW - wave elevation

KW - heave motion

KW - parametric study

UR - http://www.sciencedirect.com/science/article/pii/S0029801817302998

U2 - 10.1016/j.oceaneng.2017.06.004

DO - 10.1016/j.oceaneng.2017.06.004

M3 - Article

VL - 141

SP - 176

EP - 204

JO - Ocean Engineering

T2 - Ocean Engineering

JF - Ocean Engineering

SN - 0029-8018

ER -