海底管道沙粒侵蚀的数值模拟及侵蚀公式评价

海底管道中颗粒侵蚀是油气输送过程面临的一个重要问题,也是流动保障的一个重要分支。弯头和T型堵头管是油气生产中最易于发生颗粒侵蚀的管道组件。首先使用剪切压力传输模型(SST)计算管道内流场,使用拉格朗日方法跟踪颗粒运动轨迹,结合颗粒随机反弹模型,建立跟踪复杂流场中大规模颗粒运动轨迹的一般方法;之后引入四种颗粒侵蚀公式,预测弯头、T型堵头管的砂粒侵蚀结果,并结合实验数据,比较分析各侵蚀公式的精度与适用性。分析结果表明,对于弯头,四种侵蚀公式的数值结果与实验结果均吻合良好,其中Tabakoff的侵蚀公式具有较高的精度和较好的适用范围;对于T型堵头管,数值方法对颗粒运动机理的模拟尚存缺陷,需做进一步改进。     

垂直提升管道输送过程中的流固耦合效应分析

以垂直悬臂提升管道为研究对象,应用有限元软件ADINA对其输送过程进行流固耦合效应特性分析。本文应用有限元软件ADINA对扬矿管道进行管内流体—管道—管外流体三者流固耦合模态分析。首先建立了扬矿管道流固耦合有限元模型,得到了不同输送矿石体积浓度、管道截面尺寸下的前6阶固有频率和振型,继而比较了上述条件下三者耦合、二者耦合及无耦合情况的固有频率,讨论了流固耦合作用对管道固有频率的影响。研究结果表明:(1)扬矿管道流固耦合效应下其固有频率随着管内输送矿石颗粒浓度的增大而降低,考虑管内流体—管道—管外流体三者流固耦合时的管道固有频率较只考虑管内流体—管道二者耦合和不考虑流固耦合时要小,影响系数也相应降低;(2)流体对管道流固耦合固有频率的影响程度随着相对厚度d值的增大而减小,在考虑管内流体—管道—管外流体三者流固耦合时管道固有频率较只考虑管内流体—管道二者耦合相对误差增大;(3)在实际的扬矿管道输送中应该考虑输送流体颗粒浓度、不同相对管道壁厚、管内流体—管道—管外流体三者流固耦合作用对固有频率的影响,尽量使管道固有频率远离工作频率,避免共振情况的发生分析结果对扬矿管道的动态响应计算、结构设计和减振研究具有一定的指导意义。     

钢悬链线立管与海床土体接触问题的ANSYS有限元分析

钢悬链线立管(SCR)与海床土体的接触问题对立管的疲劳寿命影响很大.运用ANSYS有限元软件中的接触单元模拟SCR与海床接触处的相互作用,考虑海床土体的非线性,建立SCR与海床系统有限元模型,并同已有的等价梁-弹簧模型进行了比较和验证.运用该模型进行计算分析,探讨了管道重量、土体模型和摩擦系数等对管道入土深度和弯矩的影响,为进一步研究SCR与海床的相互作用提供参考.     

基于动力条件改变的笔架山连岛坝侵蚀原因分析

利用MIKE21软件的波浪谱模型及潮流模型对辽宁锦州大笔架山岛连岛坝海域的波浪、潮流等水动力条件进行了数值计算,并对锦州港建设前后的动力条件变化进行了分析.结果表明：锦州港的建设完全阻断了偏西向波浪对连岛坝的塑造作用,坝体的侵蚀确系单侧（偏东向）波浪作用的结果,坝体局部侵蚀严重区域形成四处明显的潮沟,潮沟处流速增大,加剧了对坝体的侵蚀.     

海底管道水下气体扩散FLUENT仿真分析

海底管道气体扩散到自由表面的半径及泉涌高度是进行水下气体泄漏风险分析的关键因素。利用FLUENT软件中的VOF模型和DPM模型耦合方式,对海底管道气体竖向扩散进行了仿真。模拟了水气两相交界面的行为,研究了气泡粒子扩散过程,分析了气泡粒子的扩散半径及轴向位移,讨论了不同泄漏速率对水下气体上升时间及水气两相交界面中泉涌高度的影响。通过模型中的水气两相交界面中泉涌高度和上升时间与实验结果的比较,验证了模型在一定条件下的正确性。     

海底矿石软管中水力输送数值模拟研究

海底矿石在软管中的水力输送是深海采矿的重要过程。采用计算流体动力学—离散元耦合的计算方法（CFD-DEM）,对矿石颗粒在软管中的输送进行数值模拟,重点关注矿石颗粒的运动、分布规律以及管壁受到的颗粒作用力,分析输送速度和输送浓度（入射颗粒的体积分数）对输送过程的影响规律,探索管道中易发生堵塞、易受颗粒磨损的区域。结果表明,软管中颗粒的动力学特性与管道倾角、输送速度和输送浓度有关。颗粒主要沿管道截面底部推移,倾角较大的上升段出现处于悬移状态的颗粒;管道横截面内颗粒运动速度从上至下递减,截面中心处颗粒的速度接近输送速度。输送过程中颗粒的局部浓度（该区域颗粒与固液两相流的体积比）始终大于输送浓度,局部平均速度始终小于输送速度。上升段颗粒体积分数大于下降段,颗粒速度小于下降段。管道拱顶和谷底位置管壁所受颗粒作用力最明显,管壁最可能受颗粒磨损。     

多跨海底管道横流向涡激振动预报模型

基于欧拉-伯努力梁理论确定了多跨管道结构振动方程,采用非线性Van der pol方程描述旋涡脱落的尾流动力特性,利用弹簧模拟两端和中间的复杂边界约束,构建了多跨海底管道横流向涡激振动预报模型。基于模态正交性展开流-固耦合作用方程,对各阶主坐标响应进行数值求解。对比了本模型预报结果与试验结果、软件分析以及DNV规范推荐值,吻合情况比较理想。本模型可为深海多跨管道涡激振动的研究、防范和治理提供有效的分析方法。     

铺设过程中海底管道的非线性分析

本文运用弹性杆理论建立了铺设过程中海底管道的综合相容的力学模型。该模型考虑了由于管道的大挠度变形引起的几何非线性和由于流体动载荷引的的载荷非线性的影响,考虑了随管道变形而变化的边界条件。介绍了差分法在求解该非线性模型中的应用,并对如何模拟边界条件提出了一整套方法。本数值方法的结果与已有的直接积分法计算结果比较,二者吻合较好。     

轴线倾斜海底管道冲刷速率试验研究

通过物理模型试验研究水流作用下轴线倾斜海底管道的三维局部冲刷问题。利用超声波探头监测管道下部冲刷沿管轴线方向的扩展过程,分析海底管道三维局部冲刷的动态发展机理。由模型沙的冲蚀试验,建立沙床面剪切应力与泥沙表观侵蚀速率之间的关系式,并引入经验公式对沙床面剪切应力放大系数、泥沙表观侵蚀速率以及远场床面剪切应力之间的关系进行表达。由倾斜管道模型试验,在分析冲刷扩展位置随时间变化数据的基础上,结合上述经验公式以及沙床面剪切应力放大系数与管道埋深的关系,建立轴线倾斜海底管道冲刷扩展速率的预测公式。     

基于ABAQUS的卷管式铺管法管道变形敏感性分析

卷管式铺管法在海管铺设中的应用愈发广泛,在铺设作业中管道会发生几何非线性变形,导致出现复杂的力学性能变化。针对管道在上卷、退卷过程中的屈服变化过程,通过弹塑性理论进行分析,推导出管道退卷后残余轴向应力的解析解;随后利用有限元软件ABAQUS建立模型实例,对比解析解与有限元模型,两者的计算结果基本吻合。基于上述有限元模型,研究上卷时的张力和退卷时的后张力对椭圆度、截面轴向应力和剪切应力的影响,并进行敏感性分析。模拟结果表明张力和后张力变化会影响管道截面的变形程度,退卷后截面上残余的轴向应力远高于剪切应力,并且通过敏感性分析,得到了残余椭圆度、残余应力随张力和后张力变化的规律。研究可为卷管铺设过程中张力和后张力的选择提供参考和借鉴。     

海上大直径钢管桩打桩过程中桩周土强度弱化研究

海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。     

Phylogenetic diversity and phenotypic characterization of cultivable bacterioplankton isolated from polar oceans

A set of 27 marine planktonic bacteria isolated from the polar regions was characterized by 16S rDNA sequencing and physiological and biochemical testing. More than half of these bacteria were positive for caseinase, gelatinase and 13-glucosidase, and could utilize glucose, maltose or malic acid as carbon source for cell growth. Twelve isolates expressed nitrate reduction activities. Except for one antarctic isolate BSwlO175 belonging to Actinobacteria phylum, these isolates were classified as γ-Proteobacteria, suggesting that γ-Proteobacteria dominated in cultivable marine bacterioplankton at both poles. Genus Pseudoalteromonas was the predominant group in the Chukchi Sea and the Bering Sea, and genus ShewaneUa dominated in cultivable bacterioplankton in the Prydz Bay. With sequence similarities above 97%, genus Psychrobacter was found at both poles. These 27 isolates were psychrotolerant, and significant 16S rDNA sequence similarities were found not only between arctic and antarctic marine bacteria （ 〉 99% ）, but also between polar marine bacteria and bacteria from other aquatic environments （ ≥ 98.8% ）, including temperate ocean, deep sea, pond and lake, suggesting that in the polar oceans less temperature-sensitive bacteria may be cosmopolitan and have a bipolar, even global, distribution at the species level.     

Estimation of Sediment Properties during Benthic Impact Experiments

Sediment properties, such as water content and density, have been used to estimate the dry and wet weights, as well as the volume of sediment recovered and discharged, during benthic impact experiments conducted in the Pacific and Indian Oceans. The estimates show that the weights of dry (355-1332 t) and wet sediment (1651-4888 t) recovered during the experiments, are not only a function of the total duration and distance covered during the experiment, but also depend on water content and density of the sediment. Estimation of dry sediment and its volumetric ratio in the discharge, are key parameters for calculating the discharged volume. The estimated volume of wet sediment recovered (1427-4049 m 3 ) as well as discharged (2693-6951 m 3 ) during the experiments, provide important inputs to evaluate the sediment resettlement and migration. Using these estimates, the average depth of excavation on the seafloor, can also been calculated. However, the stages of sediment recovery and discharge are expressed differently in some of the experiments. In order to standardize these, different stages have been identified, and definitions of certain terms have been suggested, for use in the future. The methods of calculating different properties, as well as weight and volume of discharged sediment are described in the paper for use in other applications concerning deep-sea discharges.     

A Tidal Flow Model for the Gulf of Kachchh, India

A vertically integrated model has been used to study the tidal circulation and currents in the Gulf of Kachchh along the west coast of India. The model is fully nonlinear and uses a semiexplicit finite difference scheme to solve the basic hydrodynamic equations on a staggered grid. The model is forced by prescribing the tides along the open boundary of the model domain. The flow is simulated both with and without the presence of the proposed tidal barrage across the Hansthal Creek in the Gulf of Kachchh. The results show a considerable change in the behavior of the tidal flow in the presence of the barrage.     

利用中国GF-3卫星SAR和HY-2A卫星微波散射计的首次台风联合定量观测

<正>The typhoon,as a mature tropical cyclone that develops in the western part of the North Pacific Ocean with high wind speed and heavy rainfall,is one of the most lethal and costly of natural disasters for the densely populated countries of East Asia.It can be easily detected by space-borne sensors operated at microwave,visible or infrared bands(Liu et al.,2014).Synthetic Aperture Radar(SAR)is     

离子交换—原子吸收光谱法测定海水中痕量铜、铅、锌、镉、铁、锰

本文介绍了用国产D401型螯合树脂分离富集海水中铜、铅、锌、镉、铁、锰等痕量元素,并用原子吸收光谱仪测定其含量的方法。讨论了各元素的分离条件选择及干扰元素的影响,并与溶剂萃取法的结果作了比较。各元素检测的定量下限为:铜0.5μg/L、铅0.1μg/L、锌1.0μg/L、镉0.01μg/L、铁2.0μg/L、锰2.0μg/L。方法精密度在4—8％之间,回收率为90—102％。     

Biogeochemistry of Mangrove Soil Organic Matter: a Comparison BetweenRhizophoraandAvicenniaSoils in South-eastern Brazil

Soil core samples fromRhizophora mangleL. andAvicennia schauerianaStapf & Leech forests from south-eastern Brazil were analysed for their total organic matter content and their sugars, amino acid and amino sugars composition. Organic carbon and nitrogen contents were higher inAvicenniathan inRhizophorasoils. The contribution of sugars and amino acids to the total organic carbon pool was constant with depth inRhizophorasoils whereas inAvicenniasoils it increased. Spectral distribution of sugars and amino acids showed a dominance of Ca-affine monomers, particularly acidic amino acids, and the sugar arabinose. Biogeochemical indicators derived from ratios of individual sugar and amino acid monomers confirm previous studies which showed that organic matter in both soils is mainly of mangrove origin. The results further suggest accumulation of organic matter inRhizophorasoils and a continuing degradation of organic matter inAvicenniasoils. The latter may thus release more nutrients to adjacent ecosystems thanRhizophorasoils.     

A review of orange roughy Hoplostethus atlanticus fisheries,estimation methods,biology and stock structure

Orange roughy Hoplostethus atlanticus are unusual fish. They form dense aggregations that have fuelled lucrative fisheries at great depths (600–1 400 m), especially off Namibia, New Zealand and Australia. They are thought to be very long-lived (>100 years, maturity at 22 – 40 years), and to have exceptionally low natural mortality (M = 0.045–0.064 year^?1) and slow growth rates (K = 0.055–0.070 year^?1). In addition, they spawn large eggs and have low fecundity. These factors combine to make orange roughy highly susceptible to overfishing; most stocks are below 30% of pristine levels. Assessments are obtained from indices of catch rate and trawl, acoustic and egg surveys. Acoustic estimates are the most direct, but are confounded by the species' low target strength (?50 to ?53 dB)–attributable to the wax-filled swim bladder. Extracellular wax esters are stored in abundance and comprise mostly mono-unsaturated fatty acids, with low concentrations of the ω-3 fatty acid family. This unusual composition (resultant from the species' diet) ensures neutral buoyancy. Stock separation has been inferred mainly from biological studies, but genetic studies have also found differences among stocks within New Zealand and Australia. Deep-water habitat may be damaged by trawling operations and may take many years to recover, so in some quarters there is a call for a portion of suitable habitat to be set aside for preservation. Although Namibian orange roughy are shallower, smaller and younger than those in other stocks, the Namibian fishery sustained high catches for only a few years before quotas were reduced, from 12 000 to 1 875 tons. Three management lessons are suggested for developing orange roughy fisheries based on the Namibian experience: (1) imposition of catch limits during exploratory fishing; (2) starting the acoustic surveys earlier in the fishery, if possible; (3) greater reliance on trends in catch rate until a survey series has been established.