海底管道的弹塑性稳定性和屈曲传播

本文根据我国南海海底输油气铺管的要求系统分析了海底管道在弯曲与外水压力共同作用下的弹塑性稳定性和屈曲传播.研究了管道的极值型屈曲和分枝型屈曲.在考虑管道的初始非圆度和材料的物理非线性的情况下提出了临界屈曲载荷的计算方法.综述和评论了屈曲传播现象的本质和各种计算方法.介绍了我们所进行的全尺寸管道实验.在分析理论结果时与现行的有关设计规程进行了比较和评论.     

Numerical investigations of supercavitation around blunt bodies of submarine shape

Cavitation occurs when liquid is subjected to rapid changes of pressure. If the local pressure is lower than the liquid saturation pressure, the liquid changes its phase into vapor. A fast moving solid body underwater will reduce the local pressure around the body. Under certain conditions, the local pressure can be lower than the water saturation pressure, accordingly causing cavitation. If the velocity of the moving body increases further, a supercavitation will occur. In this paper, the cavitation and supercavitation were studied by the SST k–ω turbulence model combined with a finite-rate mass transfer modeling under the mixture assumption. The validations of these models were performed through comparisons between numerical simulations and experiments. After the validations, the supercavitation generated by a high speed moving body, which can be described as a large bubble, was studied. The studies were on several blunt bodies, such as a submarine hull shape, a submarine hull shape with appendages and a full submarine shape with sail and appendages. It was found that the naked submarine hull is difficult to have the supercavitation covering the whole body. The sail and appendages can help supercavitation occurs earlier. Furthermore the effects of the supercavitation on the submarine and generation mechanism of the supercavitation is discussed based on the simulations.     

海底地下水排泄及其对沿海海域生态环境的潜在影响

海底地下水排泄(SGD)是海岸带陆海相互作用的一个重要的自然过程.系统介绍SGD的发生过程及其定量测定的方法,并通过水文计算和野外调查,在估算了区域海底地下水排泄量和分析了海水与地下水中氮、磷、碳等营养物质差异的基础上,讨论了SGD对近海海域生态环境的潜在影响,这对正确区分近岸海域营养物质的来源和认识中国沿海水域频繁发生的赤潮藻暴发性增殖事件的原因,具有重要的理论和实践意义.     

粘质海底稳定性实例分析

本文对南海珠江口盆地大陆架区和东海浙江沿岸象山港的粘质海底进行了稳定性分析。通过实例分析判定了该地区不稳定性的原因, 并给出了稳定性估计的直观图。文中还指出了今后研究的方向。     

Assessment of Submarine Antennas for Millimeter-Wave Satellite Communication

This communication examines the theoretical basis for estimating the maximum gain of proposed millimeter-wave antenna systems when the space available for such antennas in the submarine mast is fixed. Limits derived in Harrington's classic paper are found to be applicable. The role of the gain-bandwidth product in assessing the system performance is also discussed.     

Acoustic signature of a submarine hull under harmonic excitation

The structural and acoustic responses of a submarine under harmonic force excitation are presented. The submarine hull is modelled as a cylindrical shell with internal bulkheads and ring stiffeners. The cylindrical shell is closed by truncated conical shells, which in turn are closed at each end using circular plates. The entire structure is submerged in a heavy fluid medium. The structural responses of the submerged vessel are calculated by solving the cylindrical shell equations of motion using a wave approach and the conical shell equations with a power series solution. The far-field radiated sound pressure is then calculated by means of the Helmholtz integral. The contribution of the conical end closures on the radiated sound pressure for the lowest circumferential mode numbers is clearly observed. Results from the analytical model are compared with computational results from a fully coupled finite element/boundary element model.     

西南印度洋超慢速扩张脊海底热液硫化物中金银矿物的富集特征及富集机制研究

通过电感耦合等离子体光谱仪(ICP-AES)以及扫描电镜等手段对超慢速扩张的西南印度洋中脊热液区的3个硫化物样品的金银含量及其赋存状态进行了研究。通过ICP-AES测定金银含量,结果发现3个样品均有Au和Ag富集的现象。通过能谱-扫描电镜联用(SEM/EDS),在三个样品中发现了大量的金银矿物。其中S27-4中,主要以不规则粒状的银金矿和自然金的形式赋存于硫化物中或者晶粒之间,而S35-22中,则发现了大量的银矿物和部分银金矿。能谱分析表明银矿物中常伴随有一定量的卤族元素,推测以卤化银的形式存在,银金矿除了以粒间金赋存还可以呈乳滴状被吸附在黄铁矿表面或者晶棱上,推测与黄铁矿表面缺陷有关。S35-17样品中银金矿是唯一被发现的矿物相,以包体金、吸附金和间隙金形式赋存。由于不同样品中,银金矿的摩尔比有所不同,指示形成环境有所不同。研究结果表明,S27-4的成矿流体中,Ag主要以AgCl-₂络合物迁移,Au经历了以AuCl-₂络合物到AuHS0络合物为主的转变,指示了其温度从中高温到中低温的变化过程,说明了传导冷却在这个变化过程中有重要作用。S35-22中金银矿物的形成也具有类似的富集机制,但S35-22中卤化银的形成显示了早期高温高氯度的流体环境。而黑烟囱样品S35-17中银金矿的形成则与热液流体与海水的混合作用有密切关系。     

基于声场精细积分算法的潜艇流激噪声预报

建立了Suboff潜艇流场、结构场和声场耦合模型,对其水下航行时流激引起的艇体低频结构振动及水下辐射噪声进行了研究。采用CFD方法对潜艇三维流场进行非定常计算,以此得到艇体表面的脉动力,并通过数据映射将该脉动力加载到潜艇有限元模型进行响应分析。以潜艇壳体响应结果为边界条件,采用声场精细积分算法对潜艇流激引起的水下辐射噪声进行预报,该算法可对Helmholtz边界积分方程(HBIE)中的弱奇异积分系数及近场积分系数进行自适应求解,当细化步数达到6时,积分以10-4的残差单调收敛。结果表明,流激作用下,潜艇水下辐射声功率及声辐射效率皆出现明显峰值,其中流激的线谱成份引起艇体受激强迫振动,辐射较强水声,宽带谱成份则引起艇体结构共振,可辐射更强的水声。因此,降低潜艇的流激噪声,需同时优化艇体型线及内部结构以改善伴流,降低湍流强度,重点是避免流激共振。     

Imaging of echo data of submarine sedimentary beds layer-by-layer with acoustic wave equation refraction correction method

I.IntroductionThcobjcctofsubmarincstratasurvcyisforgco1ogicalintcrprctation,inwhichsubmarinccchodataarcuscd.Rightgcologicalintcrprctationisbascdonthedatawithhighsignal-to-noiseratio(S/N)andhighrcsoIution.ThcusualmcthodofimprovingS/Nistocollcctwide-anglcechodatahyasystcmcomposcdofanacousticsourceandahydrophoncsfrcamcrtOwedbchindaprofilerandstackthcdataincommon-dcpth-point(CDP)gathcr,whichcansupprcsssomctypcsofintcrfcrcnce.a..s[1'2].Bcsidcs,combincdmcthodsoffic1dco11cctionandfi1teringmcthods…     

分体式原向反射法水下武器速度测试技术研究

水下动态参数的测试是特种武器、两栖武器、水下专用武器性能考核的必备环节，而水下运动体的速度信息是评价水下武器性能的重要指标之一。针对现有的水下高速目标参数测试系统中存在的成本高、安装调试复杂、设备体积庞大等问题，提出一种以激光光幕为有效区域水上、水下分体式，实时、非接触的测速方法。通过分析Lambert-Beer定律和体散射函数等数学原理，确定了水下光谱传输规律综合考虑性价比获得最佳峰值波长；将1m的圆柱体作为散射体模拟光在水中的散射情况，追迹空间区域内的光线总数为1×105，获得位于传播方向上1，3，5和7 m处的接收面上辐照度的光能量分布，从而获取系统激光光源的最佳峰值功率。以此为依据，采用定距测时原理和一维原向反射技术，由峰值波长为532 nm的半导体光纤耦合绿光激光器、光纤耦合式鲍威尔棱镜防水扩束器、一维原向反射器等构建光学系统。激光光源、光电转换部分和信号调理部分位于水上，激光光幕和原向反射器位于水下，通过光纤束完成两路光信号的发射和反射光的回收。发射端光纤一端与光源耦合，另外一端与鲍威尔棱镜耦合置于水下形成扇形光幕。接收端光纤一端均布于鲍威尔棱镜出口，另一端与PIN型光电传感器耦合。设计齿形一维原向反射器并完成加工制造，光线将沿着入射光方向原向返回，另外一维方向则仍为镜面反射，将接收系统置于发射点垂直光面内附近即可接收大部分光能量，解决了现有原向发射器因水介质折射率不同于空气而导致原向反射特性消失的问题。实验采用波长为(532±5) nm绿光激光器，功率稳定性<1%，光学噪声< 0.5%，准直后耦合至长度为2 m的单模光纤再经过鲍威尔棱镜展宽为60°扇形一字线光幕，扩束模块封装采用尼龙防水材料，接收光纤均布于光源周围形成环形光纤束，光纤另外一端均匀排列与PIN光敏二极管直接耦合。光敏二极管前加中心波长为532 nm的光学滤光片，FWHM=(3±1) nm，透过率为70%。PIN型光敏二极管有效尺寸为5.0 mm×5.0 mm。采用多档可调的光电信号调理电路以适应不同尺寸的测试对象。该系统进行了不同目标速度参数测试实验，以钢弩为发射装置，信号经过光纤回收、信号调理，采集至计算机处理获得波形及区间内平均速度，两激光光幕之间的距离为定值300 mm，波形峰值作为计时时刻。成功获取了较高信噪比的波形信号和目标速度值。利用水下运动体模型与模拟结果进行比较得到其绝对误差。实验结果表明： 本方法结构简单、重复性好，可实现有效区域达到1 m×1 m，最小可测目标尺寸为5 mm，理论测速上限可达1 000 m·s-1，实验数据通过与理论经验公式结果比对表明，系统测试精度可达0.2%。