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《船舶力学》2016,(9)
为研究艇后非均匀流场中大侧斜螺旋桨无空泡负载噪声的分布规律,文章采用"CFD+BEM"法,以SUBOFF潜艇后某大侧斜桨为研究对象,首先稳态计算均匀进流下螺旋桨敞水特性,模拟系数值与实验误差在3%以内,验证了CFD数值计算的可信性。然后采用大涡(LES)模拟,对"艇+桨"进行三维非定常数值模拟,计算得到桨表面声偶极子数据后,通过距离加权平均法映射到声网格节点上,将噪声源直接分布在桨叶表面上进行积分来预报螺旋桨的低频线谱噪声。采用边界元法基于扇声源理论通过FW-H声类比方程分别在1 k Hz以内对桨盘面、轴向纵剖面及10倍桨半径球场的噪声进行频域求解。研究表明:桨盘面和轴向纵剖面上声指向均呈8字形,但受螺旋桨自身旋转及大侧斜的存在,指向性不唯一;球场声场显示,轴向声辐射面较大,声辐射强,径向辐射面小且辐射较弱;特征点的计算结果显示,高阶叶频声压级明显比一阶叶频低,这与物理现象相符,将特征点处结果与已发表文献进行对比,吻合性良好,并对存在的差异作出了合理的物理解释。该文为螺旋桨噪声预报介绍了一种可行的新方法。 相似文献
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水中有限长圆柱壳体辐射声场特性 总被引:1,自引:1,他引:0
理论研究有源点激励时水中有限长圆柱壳体辐射声场特性。根据圆柱壳体耦合振动理论,推导有源点激励时水中有限长圆柱壳体振动速度与辐射声压计算式,计算并分析有源点激励时水中有限长圆柱壳体振动速度分布特征、声辐射近场和远场特性。研究结果表明:随着结构阻尼增大,圆柱壳体振动能量与声辐射能量向激励点处集中,且频率越高,这种集中效应越显著。在声辐射近场,声压衰减较快,其分布规律与壳体振动分布规律相近;在声辐射远场,声压衰减规律近似为球面波衰减,声压分布具有一定指向性,且激励力作用方向为声辐射主要方向。 相似文献
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为研究艇后非均匀流场中大侧斜螺旋桨无空泡负载噪声的分布规律,文章采用“CFD+BEM”法,以SUBOFF潜艇后某大侧斜桨为研究对象,首先稳态计算均匀进流下螺旋桨敞水特性,模拟系数值与实验误差在3%以内,验证了CFD数值计算的可信性。然后采用大涡(LES)模拟,对“艇+桨”进行三维非定常数值模拟,计算得到桨表面声偶极子数据后,通过距离加权平均法映射到声网格节点上,将噪声源直接分布在桨叶表面上进行积分来预报螺旋桨的低频线谱噪声。采用边界元法基于扇声源理论通过FW-H声类比方程分别在1 kHz以内对桨盘面、轴向纵剖面及10倍桨半径球场的噪声进行频域求解。研究表明:桨盘面和轴向纵剖面上声指向均呈8字形,但受螺旋桨自身旋转及大侧斜的存在,指向性不唯一;球场声场显示,轴向声辐射面较大,声辐射强,径向辐射面小且辐射较弱;特征点的计算结果显示,高阶叶频声压级明显比一阶叶频低,这与物理现象相符,将特征点处结果与已发表文献进行对比,吻合性良好,并对存在的差异作出了合理的物理解释。该文为螺旋桨噪声预报介绍了一种可行的新方法。 相似文献
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[目的]螺旋桨噪声和水动力噪声是潜艇噪声控制的重点和难点,因此有必要开展艇桨一体的螺旋桨激振力和水动力噪声预报研究。[方法]以SUBOFF潜艇和DTMB 4383桨为计算对象,结合大涡模拟湍流模型和无限元方法,分析潜艇非均匀伴流场中螺旋桨激振力的变化规律,以及螺旋桨对潜艇表面压力场的影响。采用ACTRAN声学计算软件对艇桨一体的水动力噪声性能进行数值预报。[结果]计算结果表明:螺旋桨激振力的各个分量具有相同的脉动频率,脉动峰值以一阶叶频处为主,同时水平力脉动和垂直力脉动大于推力脉动;潜艇艏部、指挥台、艉翼及螺旋桨叶梢部位均存在局部高压区,这是水动力噪声的主要贡献点;艇桨一体的水动力噪声主要集中在低频段,随着频率的增加,其蝶形分布更加明显;与无桨全附体潜艇相比,带桨潜艇特征点的声压值急剧增加,对其辐射声场的影响较大。[结论]研究成果可为艇桨一体的螺旋桨设计提供参考建议。 相似文献
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《船舶与海洋工程学报》2014,(2)
正In the paper"Influence of Fouling Assemblage on the Corrosion Behaviour of Mild Steel in the Coastal Waters of The Gulf of Mannar,India"in Vol.12,No.4,Page:509,References were lost,and the two authors’biographies were identical.The correct text is shown below.We apologize to the authors and our readers for any inconvenience caused by the errors. 相似文献
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《船舶与海洋工程学报》2014,(1):126-126
正San Francisco,California,June 8-13,2014.OMAE 2014 is the ideal forum for researchers,engineers,managers,technicians and students from the scientific and industrial communities from around the world to:·meet and present advances in technology and its scientific support;·to exchange ideas and experiences whilst promoting technological progress and its application in industry·to promote international cooperation in ocean,offshore and arctic engineering.In line with the tradition of excellence of previous OMAE conferences,more than 900 technical papers are planned for presentation.Outreach for Engineers Specialty Forum This Specialty Forum is designed for students and professionals who may not be familiar with the Ocean and Offshore industry,as well as those who have just recently specialized in this field. 相似文献
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联合作战计划和执行系统 总被引:2,自引:1,他引:1
全球指挥控制系统(GCCS)实施当前美国海军网络中心战信息基础设施的联合计划网络。联合作战计划和执行系统(JOPES)支持GCCS实现联合计划。JOPES有两类计划:时间不限的精密预案计划生成作战计划、方案计划或职能计划;时间敏感的危机行动计划生成作战命令或战役方案。前者在和平时期创建的作战计划是后者的计划基础,加速应付危机的能力。 相似文献
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Recent measurements of wave induced hull strain and flexure in RN warships are presented together with the derivation of the current design criteria for extreme hull girder bending loads. The history of the development of the shipboard instrumentation used is given and recent developments to improve the quality and ease of analysis of the data are described. An unexpectedly high transverse asymmetry in the longitudinal strains measured in destroyers is shown to be the result of a combination of vertical and lateral bending in oblique seas. Finally recent theoretical comparisons between the loading of Deep-Vee hulls and conventional UK rounded bilge hulls are presented which demonstrate the higher loading experienced by this type of hull form. 相似文献
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《船舶与海洋工程学报》2014,(1)
正19–24 October 2014 SingaporeCONFERENCE THEMES The overall aim of the ICHD Conference is to provide a forum for participants from around the world to review,discuss and present the latest developments in the broad discipline of hydrodynamics and fluid mechanics.The first International Conference on Hydrodynamics(ICHD)was initiated in 1994 in Wuxi,China.Since then,9 more ICHD conferences were held subsequently in Hong Kong,Seoul,Yokohama,Tainan,Perth,Ischia,Nantes,Shanghai and St Petersburg.Evidently the ICHD conference has become an important event among academics,researchers,engineers and operators,working in the fields closely related to the science and technology of hydrodynamics.The 11th ICHD will be held in Singapore in 2014. 相似文献
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《船舶与海洋工程学报》2014,(2)
正November 4-6,2014Moody Gardens HotelConvention Center/Galveston,TX The Deepwater Operations Conference and Exhibition is celebrating its 12th anniversary this year.This growing event will continue the tradition of excellence in addressing operational challenges involved in developing deepwater resources.We will return to the Moody Gardens Hotel and Convention Center on November 5-7,2014 in Galveston,Texas. 相似文献
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In terms of equal sailing distances, where is the inflexion when ships depart from ports in the Asian Continent to New York via Suez and/or Panama?
The answer is China South Port Group (Hong Kong, Shenzhen and Guangzhou). 相似文献
The answer is China South Port Group (Hong Kong, Shenzhen and Guangzhou). 相似文献
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Gunnar Alexandersson Staffan Hultén Frode Longva 《Research in Transportation Economics》2010,29(1):212-218
Despite the many socio-economic similarities between Sweden and Norway, differences in jurisdiction, organisation, cooperation, and financing of long-distance passenger train and coach services have led to the development of four distinctively different ways of serving the markets. This paper describes how the train and coach markets have developed in the two countries, with emphasis on regulatory and industrial structure and a couple of performance variables.Looking at passenger rail, both countries separated infrastructure from operation over a decade ago. However, while Norwegian rail is characterised by an almost monopoly supplier, rail services in Sweden are partly decentralised to the responsibility of county authorities and are widely subjected to competitive tendering. The rest of the network is about to be opened up for on-the-track competition. Swedish Rail (SJ) has spent the last decades consolidating its core business (passenger rail) and sold out its other businesses. In contrast, the Norwegian state rail (NSB) has expanded its business to become a major bus operator and property owner, with extensions also into the Swedish market.The coach industry was more recently deregulated in both countries. The Swedish coach market is dominated by privately owned companies operating services to and from Stockholm. In Norway, state-owned NSB is a major coach operator on medium distance routes, and is also the largest partner of Nor-Way Bussekspress which totally dominates long-distance coach services. Further, the Norwegian coach market is characterised by cross-ownership and cooperation which has enabled an extensive route network which covers most of Norway.We find distinct differences in achievements in the two modes and in the two countries. Swedish rail services have succeeded in winning market shares and in renewing and developing both infrastructure and service levels to a greater extent than the Norwegian model. On the other hand, the Norwegian coach market seems to be more developed and efficient compared to its Swedish counterpart.The paper concludes with a discussion on the possible links between the different approaches and the performance observed, with the aim to stimulate further and more detailed research on some important issues. 相似文献