共查询到19条相似文献,搜索用时 515 毫秒
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为使大型船舶在限制性航道航行时达到较为理想的节能减排效果,根据船舶在航道中的水动力水池试验与数值模拟试验结果,结合船舶在限制性航道的水动力特点,分析船舶航行阻力的成因和分类,提出降低船体表面粗糙度、采用合理航速、采用纵倾优化技术等易于施行的减阻对策。 相似文献
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以国际标准油船KVLCC2为研究对象,基于RANS方程,对其沿岸航行时在浅水与岸壁效应联合作用下船体周围黏性流场的变化特性进行数值模拟.对网格无关性和湍流模型进行验证,并将水动力和流场计算结果与试验值相对比,以验证数值方法的可行性.改变水深、船-岸距离和航速3个参数,计算对比周围流场的变化、船体表面压力的变化和伴流分数的变化,重点分析船尾伴流的偏移特性,给出桨盘处伴流分数的变化趋势和平均值.研究结果表明,随着水深和船-岸距离的减小,桨盘处伴流分数沿周向的分布呈不对称性;水深和船-岸距离同时减小会使桨盘处流场向岸壁偏移更明显;航速变化对流场偏移的影响较小. 相似文献
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考虑到FPSO设计为30年不进坞,需要设计满足外板防腐要求的ICCP系统,按照规范计算经验布置艏艉两套ICCP系统,通过数值仿真软件建立三维模型后进行模拟分析,校核在作业期间ICCP系统输出的保护电流以及船体各区域保护电位值。按照数值模拟结果,对ICCP系统设计进行调整和优化,数值结果表明,简单按照规范计算得出保护电流后确定的ICCP系统,存在部分区域保护电流分布不均,出现过保护或欠保护的现象。基于规范计算结果,采用数值仿真软件进行ICCP系统设计模拟分析后,针对FPSO船体外形结构型式特点,通过艏、中、艉部区域配置不同型号辅助阳极,增大辅助阳极屏蔽层面积,能够让外板保护电流更加均匀分布,保持合理的保护电位。 相似文献
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《中国航海》2019,(4)
为更全面研究半潜船航行耐波性特性,以某5万吨级半潜船为研究对象,分别通过耐波性模型试验、实船试验和三维水动力数值模拟方法研究该半潜船在不同海况下的水动力运动响应,获得非零航速状态下船体垂荡、横摇、纵摇运动响应幅值(Response Amplitude Operator,RAO)响应曲线和两个参考点的垂向、横向加速度统计有义值。计算结果表明装载状态和浪向对该半潜船航行耐波性有较大的影响,实际营运中应避免相关不利因素造成的影响。此外,通过数值模拟与模型试验和实船试验的对比分析,验证数值模拟方法的可靠性,表明该方法可有效地预报半潜船航行耐波性,是半潜船货物绑扎分析有力的技术保障。 相似文献
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为了尽量减少和防止船体金属的腐蚀,目前国外已广泛采用一种牺牲阳极法来保护船体。从六十年代中期开始,上海船厂就开始进行用锌基合金作为牺牲阳极的方法来防止船体腐蚀的试验,并取得了一定的成效。一九七五年,我厂又与上海交通大学协作,开展铝基牺牲阳极的试验工作,并且先后在“丹阳”、 相似文献
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复杂结构阴极保护设计中电流屏蔽效应数值模拟仿真 总被引:1,自引:0,他引:1
复杂结构的阴极保护优化设计是实际工程中的一个难题,本文采用以边界元法为基础的数值模拟仿真技术,模拟计算潜艇上层建筑区域阻挡式和吸收式2类电流屏蔽效应的影响.研究结果表明,复杂结构阴极保护设计中结构电流屏蔽效应的影响随着遮挡物高度的变化而变化,当该遮挡物小于一定值后,阻挡屏蔽效应影响消除;气瓶等设备对保护电流的屏蔽效应明显,阻碍阳极提供保护电流.气瓶、高电位金属管路等设备与艇体间的绝缘措施良好时,不产生吸收式屏蔽效应;气瓶、高电位金属管路等设备与艇体结构间的绝缘措施失效时,将产生吸收式的屏蔽效应.对于潜艇上层建筑这种非常复杂结构阴极保护系统的设计,基于边界元法的数值仿真是一种有效的方法. 相似文献
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舰船舷侧防护结构水下接触爆炸动响应分析研究 总被引:1,自引:0,他引:1
舰船舷侧防护结构在接触爆炸载荷作用下的动响应问题是舰船抗爆抗冲击设计的重要组成部分。根据国外水面舰船防护结构形式,在某单层舷侧舰船模型基础上增设舷侧防护隔壁结构,并应用国际上通用的动力有限元程序ABAQUS对其进行水下接触爆炸系列数值仿真实验,考核舷侧防护结构对舰船抗爆抗冲击性能的影响。通过结果的对比分析发现,增设舷侧防护结构后较明显改善了船体外板的损伤情况,且防护隔壁仅发生了少量的塑性变形没有产生破口,从而达到了保护内部机舱等重要舱室的目的,并以防护结构双层隔舱内填充液体抗冲击性能最佳。 相似文献
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在梳理流噪声数值预报方法的基础上,采用流场大涡模拟(large eddy simulation,LES)和声学边界元(boundary element method,BEM)方法在频域内计算预报了船体流噪声谱曲线,求取了其等效声中心.LES计算时选用动力学Smagorinsky-Lilly(dynamic Smagorinsky-Lilly,DSM)亚格子应力模型,流噪声由船体壁面脉动压力和法向速度特性决定,声源节点和声节点变量传递采用一对一的守恒传递方式.结果表明:某型船在航速14 kn时,裸船体流噪声在20 Hz~2 kHz频段内总声源级为133dB;当计算有效频段扩展到20 kHz时,总声源级达143.3 dB.流噪声主要来源于兴波引起的涡量,且主要集中于100 Hz~10 kHz频段.球首尾流区和船体尾涡区对流噪声辐射量贡献明显,特别是球首尾流区,对全频段都有明显的贡献,为水面舰艇流噪声研究提供了一条新的途径. 相似文献
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《船舶与海洋工程学报》2016,(2)
In this paper, the effects of zinc(Zn) and magnesium(Mg) addition on the performance of an aluminum-based sacrificial anode in seawater were investigated using a potential measurement method. Anodic efficiency, protection efficiency, and polarized potential were the parameters used. The percentages of Zn and Mg in the anodes were varied from 2% to 8% Zn and 1% to 4% Mg. The alloys produced were tested as sacrificial anodes for the protection of mild steel in seawater at room temperature. Current efficiency as high as 88.36% was obtained in alloys containing 6% Zn and 1% Mg. The polarization potentials obtained for the coupled(steel/Al-based alloys) are as given in the Pourbaix diagrams, with steel lying within the immunity region/cathodic region and the sacrificial anodes within the anodic region. The protection offered by the sacrificial anodes to the steel after the 7th and 8th week was measured and protection efficiency values as high as 99.66% and 99.47% were achieved for the Al-6%Zn-1%Mg cast anode. The microstructures of the cast anodes comprise of intermetallic structures of hexagonal Mg3Zn2 and body-centered cubic Al2Mg3Zn3. These are probably responsible for the breakdown of the passive alumina film, thus enhancing the anode efficiency. 相似文献
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能量耗散效应的多域边界元法(英文) 总被引:1,自引:0,他引:1
段文洋 《船舶与海洋工程学报》2012,11(1):18-23
The wave diffraction and radiation around a floating body is considered within the framework of the linear potential theory in a fairly perfect fluid.The fluid domain extended infinitely in the horizontal directions but is limited by the sea bed,the body hull,and the part of the free surface excluding the body waterplane,and is subdivided into two subdomains according to the body geometry.The two subdomains are connected by a control surface in fluid.In each subdomain,the velocity potential is described by using the usual boundary integral representation involving Green functions.The boundary integral equations are then established by satisfying the boundary conditions and the continuous condition of the potential and the normal derivation across the control surface.This multi-domain boundary element method(MDBEM) is particularly interesting for bodies with a hull form including moonpools to which the usual BEM presents singularities and slow convergence of numerical results.The application of the MDBEM to study the resonant motion of a water column in moonpools shows that the MDBEM provides an efficient and reliable prediction method. 相似文献
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Abubakar Muazu Yaro Shehu Aliyu Malik Abdulwahab Abimbola Patricia Idowu Popoola 《船舶与海洋工程学报》2016,15(2):208-213
In this paper, the effects of zinc (Zn) and magnesium (Mg) addition on the performance of an aluminum-based sacrificial anode in seawater were investigated using a potential measurement method. Anodic efficiency, protection efficiency, and polarized potential were the parameters used. The percentages of Zn and Mg in the anodes were varied from 2% to 8% Zn and 1% to 4% Mg. The alloys produced were tested as sacrificial anodes for the protection of mild steel in seawater at room temperature. Current efficiency as high as 88.36% was obtained in alloys containing 6% Zn and 1% Mg. The polarized potentials obtained for the coupled (steel/Al-based alloys) are as given in the Pourbaix diagrams, with steel lying within the immunity region/cathodic region and the sacrificial anodes within the anodic region. The protection offered by the sacrificial anodes to the steel after the 7th and 8th week was measured and protection efficiency values as high as 99.66% and 99.47% were achieved for the Al-6%Zn-1%Mg cast anode. The microstructures of the cast anodes comprise of intermetallic structures of hexagonal Mg3Zn2 and body-centered cubic Al2Mg3Zn3. These are probably responsible for the breakdown of the passive alumina film, thus enhancing the anode efficiency. 相似文献