Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering ConferenceShanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

The Influence of the Breakwater Layout and its Cover Area
on the Motion Response of Semi-submersible PlatformYuanyuan Wang1、Zhen Chen1、Gang Xu1,2
1

School of Naval Architecture and Ocean Engineering, Jiangsu University of Science and Technology, Zhenjiang, China
2Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, Chinacover effect.

characteristics. Lin Shangfei et al. (2013) carried out overall physicalmodel tests for different plane layout schemes in the project andmeasured the wave height in the harbor. Du Qinghua. (2014) conducteda study on the calculation of wave elements in the harbor for
breakwaters with three types of layout of single breakwaters, double
breakwaters and island breakwaters. Karthick et al. (2017) designed theplane layout of the breakwater for the port, and carried out the physicalmodel experiment of the section.
Based on the models of semi-submersible platform, breakwater andsurrounding sea area, this paper uses viscous computational fluid
dynamics software ANSYS-Fluent to establish a 3-D numerical flume
based on N-S governing equations to study the influence of breakwaterlayout type and cover area on the platform motion response.
Considering the limitation of computing cost, this paper only focuseson the heave and pitch motion of the platform under the sea conditionof head waves.

INTRODUCTIONVALIDITY VERIFICATION OF NUMERICAL WAVE POOL

Under normal circumstances, the Marine environment is complexedand changeable, and, hence, protective measures for its normal function
should be taken. Otherwise, in the case of bad sea conditions, there may
be some safety accidents, causing economic losses, or even causing
significant environmental damage and casualties. The research showsthat breakwaters demonstrate a significant shielding effect, and thelayout of breakwaters in the harbor area (such as islands and reefs in
the South China Sea) can effectively reduce the movement response
amplitude of platforms in the area. Therefore, it is necessary for us tostudy the motion response of offshore platform and the shielding effectof breakwater. Park et al. (2003) predicted the force on a platform
based on the viscous flow theory, and Queutey et al. (2004) studied theinteraction between a single cylinder and waves by using the VOF(Volume of Fluid) method. In addition, a large number of scholars haveestablished numerical wave pools based on CFD (Computational FluidDynamics) technology, successfully simulating the interaction between
various waves and structures, and calculating and analyzing the waveforce, wave climb and bang load on structures (Lee et al., 2007; Dengand Li, 2011; Cao and Wan, 2012). adjusted the original breakwaterlayout according to the actual engineering problems, modified thebreakwater axis, breakwater head layout and structure type, and carriedout model tests on the new layout scheme to verify its wave-dissipating

The spatial coordinates adopt 3-dimensional Cartesian coordinatesystem. The wave propagation direction in the 3-dimensional numericalwater tank is the positive direction of X axis, and the vertical directionis the positive direction of Z axis. The length, width, and height of thenumerical pool are 25m, 3m, and 6m respectively. The working area is15m long, the wave suppression area is 10m long, the water depth
below the free surface is 4m, and the area above the free surface is 2m
high. The two-dimensional projection of the pool is shown in Fig. 1. In
the figure, A1, A2, A3 and A4 respectively represent half wavelength,
one wavelength, two wavelength and the end of the pool. Monitoring
points are selected at x=2.5m, x=5m and x=10m to observe the changeof wave height. The resulting fluid phase diagram and wave timehistory curve are shown in Figs. 2~5.

ABSTRACTIn this study, the motion response of a typical semi-submersible
offshore platform with six columns is analyzed for two scenarios: withor without the cover of breakwater. The influence of the cover area andlayout of breakwater on the motion response of the platform has been
investigated to study the cover effect of the breakwater. The numericalsimulation results showed that the cover effect of the breakwater isaffected by the total cover area, which is in front of the semisubmersible platform and it is not only affected by the projected areaon the platform. The cover effect of asymmetrical breakwater layout isbetter than that of symmetrical layout, and this effect is more obvious
in the case of having three breakwaters.

KEYWORDS: Semi-submersible; breakwater; motion response;

Fig.1 The 3-D projection of domain

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