﻿ 畸形波作用下FPSO甲板上浪研究
 舰船科学技术  2023, Vol. 45 Issue (24): 116-121    DOI: 10.3404/j.issn.1672-7649.2023.24.021 PDF

1. 中海油研究总院有限责任公司, 北京 100028;
2. 国家能源深水油气工程技术研发中心, 北京 100028;
3. 中国海洋大学 工程学院 山东 青岛 266100

Research on green water of FPSO under freak wave
LI Hui1,2, XIE Wen-hui1,2, LV Bai-cheng1,2, WU Xu1,2, XU Ming-qiang3
1. CNOOC Research Institute Co. Ltd., Beijing 100028, China;
2. National Energy Deepwater Oil and Gas, Beijing 100028, China;
3. College of Engineering, Ocean University of China, Qingdao 266100, China
Abstract: Green water and slamming loads are one of the key factors in ship design. To investigate the green water and the wave slamming distribution of the ship under wave loads, the wave-floating body time domain coupling model is established by using smooth particle dynamics method. Based on the measured marine environmental parameters, the green water and the wave slamming of FPSO under the freak waves and regular waves are studied. Firstly, the simulation results of freak waves are verified, and then the research results under the freak waves are compared with those under the regular waves. The research results show that the pitch amplitude of the ship under the freak wave loading is 1.3 times of that under the regular wave loading, and the slamming load is 1.25 times of that under the regular wave loading. The value of the slamming load calculated based on regular waves is too small.
Key words: FPSO     freak wave     green water
0 引　言

1 数值方程 1.1 光滑粒子法基本方程

 $F(r)=\int F(r')w(r-r',h) {\rm{d}}r' 。$ (1)

 $F(r_i)\approx\sum_j F(r_j)\cdot \omega\left(r_i-r_j,h\right)\frac{m_j}{\rho_j}。$ (2)

 $\omega \left( {{r_i} - {r_j},h} \right) = {\alpha _D}{\left( {1 - \frac{q}{2}} \right)^4}\left( {{2}q + {1}} \right) 。$ (3)

 $\frac{{{\rm{d}}\nu }}{{{\rm{d}}t}}{\text{ = }} - \frac{1}{\rho }\nabla P + g + \varGamma ，$ (4)
 $\frac{{{\rm{d}}{\rho _i}}}{{{\rm{d}}t}}{\text{ = }}\sum\limits_j {{m_i}} {\nu _{ij}} \cdot \nabla {W_{ij}} 。$ (5)

 $P{\text{ = }}\frac{{{c_0}^2{\rho _0}}}{\gamma }\left[ {{{\left( {\frac{\rho }{{{\rho _0}}}} \right)}^\gamma } - 1} \right] 。$ (6)
1.2 畸形波生成方法

 $\eta {\text{ = }}\left( {x,t} \right) = \sum\limits_{i = 1}^N {{\alpha _i}\cos \left( {{k_i}x - {\omega _i}t + {\varepsilon _i}} \right)} 。$ (7)

 $\begin{array}{l}\eta \text=\left(x,t\right)={\displaystyle \sum _{i=1}^{N}\sqrt{2PS\left({\omega }_{i}\right)\Delta \omega }\mathrm{cos}\left({k}_{i}\left(x-{x}_{f}\right)-{\omega }_{i}\left(t-{t}_{f}\right)\right)}+\\ {\displaystyle \sum _{i=1}^{M}\sqrt{2（1-P）S\left({\omega }_{i}\right)\Delta \omega }\mathrm{cos}\left({k}_{i}x-{\omega }_{i}t+{\epsilon }_{i}\right)}。\\[-20pt]\end{array}$ (8)

 $S\left( f \right) = {\beta _J}H_{_{1/3}}^2T_p^{ - 4}{f^{ - 5}}\exp \left[ { - 1.25{{\left( {{T_p}f} \right)}^{ - 4}}} \right]{r^{\exp \left[ {{{\left( {{T_p}f - 1} \right)}^2}/2{\sigma ^2}} \right]}}。$ (9)

 $\;{\beta _J}{\text{ = }}\frac{{0.0624}}{{0.23 + 0.0336\gamma - 0.185{{\left( {1.9 + \gamma } \right)}^{ - 1}}}}\left[ {1.09 - 0.01915\ln \gamma } \right] ，$ (10)

$\gamma$为谱峰升高因子，$\gamma {\text{ = }}2.4 \pm 0.3$Tp为谱峰周期。

 ${T_p} \approx \bar T/\left[ {1 - 0.532\left( {\gamma + 2.5} \right) - 0.569} \right] ，$ (11)

$\sigma$为峰形参数:

 $\sigma = \left\{ \begin{gathered} {\sigma _{\text{a}}} = 0.07，f < {f_p} ，\\ {\sigma _b} = 0.09，f \geqslant {f_p} 。\\ \end{gathered} \right.$ (12)

 $U\left( t \right){\text{ = }}\sum\limits_{i = 1}^M {\frac{{{\omega _i}{\eta _i}\left( {0,t} \right)}}{{T{r_i}}}} = \sum\limits_{i = 1}^M {\frac{{{\omega _i}{\alpha _i}}}{{T{r_i}}}\cos \left( {{k_i}\left( {0 - {x_f}} \right) - {\omega _i}\left( {t - {t_f}} \right)} \right)}。$ (13)

2 数值模型

 图 1 波浪荷载作用下FPSO数值模型示意图 Fig. 1 Schematic diagram of numerical model of FPSO under wave loads

2.1 波浪-浮体耦合模型

 图 2 数值模型测点位置的波高时程曲线 Fig. 2 Wave elevations of the numerical model at wave gauges

2.2 畸形波模型验证

 图 3 实验结果和数值结果在测点位置的波高时间序列 Fig. 3 Wave elevations of experimental and numerical results at two wave gauges

3 结果分析 3.1 FPSO甲板上浪及运动响应

 图 4 波浪作用下FPSO运动特征 Fig. 4 Motion characteristics of the FPSO under wave loads

 图 5 波浪作用下船首上浪高度 Fig. 5 The wave elevation and bow height under wave loads

 图 6 波浪荷载作用下船体纵摇变化 Fig. 6 The pitch of the ship under wave loads

3.2 船首波浪冲击

 图 7 不同波浪荷载作用下砰击压力竖向分布 Fig. 7 Vertical distribution of slamming loads with different wave loads

 图 8 不同波浪荷载作用下船体受到的波浪力 Fig. 8 Wave forces on the hull with different wave loads
4 结　语

1）基于光滑粒子法建立的数值水槽实现了对畸形波和规则波的模拟，通过与实验结果进行对比，验证了数值模型的可靠性。

2）畸形波作用下船体的纵摇幅值显著大于规则波作用下的纵摇幅值，畸形波造成的纵摇幅值比规则波大30%，本文选定工况下船体设计满足南海百年一遇条件下船体的甲板上浪要求。

3）畸形波产生的砰击荷载大于规则波产生的砰击荷载，本文选定工况下畸形波砰击荷载为规则波砰击荷载的1.25倍，船舶设计时应充分考虑极端波浪对船体砰击的影响。

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