【作者】 杨露；

【导师】 张明霞；

【作者基本信息】 大连理工大学 ， 海洋工程（专业学位）， 2023， 硕士

【摘要】 作为国际海事组织(IMO)第二代完整稳性规范中的较为典型的稳性失效模式,参数横摇现象得到学者的广泛研究,它指的是船受到参数激励作用,遭遇频率与固有频率满足一定比例,并在一定的波长、波高等波浪条件下,会在小角度横摇下发生急剧增长的大幅度横摇,对人-船-货的安全造成威胁。半潜船搭载重大件货物,尤其造价昂贵、重量较大的大型海洋平台模块远洋航行过程中,船货联合体整体重心高、受风面积大、横摇固有周期较长且容易受风浪影响,一旦遭遇恶劣海况,存在发生参数横摇的风险。研究半潜船发生参数横摇的敏感区间去进行规避,对半潜船运营阶段的安全至关重要。本文基于粘流和势流混合方法,结合两种理论优势,针对半潜船航行阶段的参数横摇进行直接预报,具体研究包括:1.横摇阻尼对横摇响应的幅值有很大影响,在缺乏船模试验条件时,为弥补势流对粘性力的忽略,采用粘流方法的CFD软件STAR-CCM+,基于重叠网格技术令半潜船在不同航速下以初始横摇15°做横摇自由衰减运动,作出消灭曲线,求得半潜船在不同航速下的横摇阻尼系数。2.使用基于势流方法的水动力学软件AQWA,对半潜船搭载超大型平台模块横摇运动做数值模拟,研究规则波中航速、波高、波长、初始激励、不同浪向以及船货联合体重心高度KG对船体发生参数横摇响应的影响,得到半潜船发生参数横摇时遭遇频率比之横摇固有频率的比值区间、波高阈值、较为危险的船货联合体重心高KG区间、以及半潜船斜浪中航行的横摇响应。3.本文计算了不规则波中半潜船在不同航速、谱峰周期T_p、有义波高H_s以及随机种子数下进行横摇运动响应。设计工况基于规则波中的波陡、航速、遭遇周期与横摇固有周期比值等环境条件,以此对比随机波中船货联合体横摇响应较之规则波的差异。研究得出上述规则波、不规则波中半潜船搭载大型海洋结构物的参数横摇敏感区间,为半潜船运营阶段的航行安全提供保障,为二代稳性衡准对半潜船的规定提供参考。更多还原

【Abstract】 As a dynamic stability failure mode in the IMO’s second generation intact stability code,parametric rolling has been widely studied by scholars,which means that when parametric resonance occurs,satisfying a certain ratio of encountering frequency and natural frequency、certain wavelength,wave height and other wave conditions,the ship will be sharply and greatly shaken under the action of parameter resonance,which brings a threat to the safety of people-ships-cargo.Semi-submersible vessels carry heavy cargo,especially expensive and heavy large offshore platform modules during ocean navigation,the overall center of gravity of the cargo complex is high,the wind area is large,the inherent period of roll is long and easy to be affected by wind and waves,once it encounters bad sea conditions,there is a danger of parameter rolling.Exploring the sensitive range of parameter rolling of semisubmersible vessels and avoid them is crucial to the safety of semi-submersible vessels during the operation phase.Based on the hybrid method that combines viscous flow and potential flow,this paper directly predicts the parameter rolling of the semi-submersible vessel in the navigation stage:1.In the absence of ship model test conditions,in order to make up for the neglect of viscous force by potential flow,the CFD software STAR-CCM+ with the viscous flow method is used,based on overlapping grid technology,making the semi-submersible ship do the roll free decay movement at the initial roll of 15° at different speeds,and makes an elimination curve to obtain the roll damping coefficient of the semi-submersible ship at different speeds.2.After the roll damping obtained,the hydrodynamic software AQWA based on the potential flow method is used to numerically simulate the roll motion of the semi-submersible ship equipped with the super-large platform module.With the simulation of AQWA,the effects of different parameters on parameter rolling response of on the hull in the regular wave of are researched,including initial excitation,speed,wave height,wavelength,the height of the combined center of gravity of the ship and cargo,and the wave directions.The ratio of encountering frequency and natural frequency,the wave height threshold,the more dangerous cargo combined center of gravity high KG interval,and whether the parameter rollover occurs when the semi-submersible ship is sailing in the oblique wave are also studied.3.This paper calculates the roll motion response of a semi submersible ship in irregular waves at different speeds,spectral peak periods Tp,significant wave heights Hs and random seed numbers.The design conditions are based on environmental conditions such as wave steepness,speed,and the ratio of encounter period to roll natural period in regular waves,in order to compare the differences in roll response of the ship cargo combination in random waves compared to regular waves.The study has determined the parameter roll sensitivity range of semi submersible ships carrying large marine structures in regular and irregular waves mentioned above,so that the study can ensure the navigation safety of the semi-submersible vessel in the operation stage.Also,the study can provide suggestions for the regulations of the second-generation stability balance for semi-submersible vessels.更多还原