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A lot of tests on ice forces on vertical cylindrical piles are conducted in the ice basin of ice laboratory in Tianjin University to identify the characteristics of ice forces on fixed platforms in the Bohai Gulf. A function of ice forces is simplified on basis of test data, and the charateristics of the ice forces including the amplitude of the force and the breaking frequency of the ice sheet is detailed by use of the Fast-Fourier-Transform method. The results show that the ice breaking frequency presents a linear relationship with the ratio of ice moving velocity to ice thickness at low velocities. At high velocities, the frequency remains constant with the increase of the ratio of ice moving velocity to ice thickness. These conclusions are compared those published in literature. 相似文献
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依据模型冰物理性质控制其力学性质的原则 ,利用能量平衡观点建立了冰内未冻结液体含量同制冰过程中的冰池温度、降温及升温时间、模型冰厚度 (喷雾时间×流量 )的理论关系 ,以其量纲表达式作为预测模型冰物理和力学参数的综合控制指标 ;通过系统测量酒精溶液冰点温度、冰池大厅气温、模型冰温度、冰内未冻液含量、冰密度、冰压缩强度、冰弯曲强度和冰变形模量 ,获得了不同冰点温度模型冰的物理和力学参数同该综合控制指标的实验关系 ;实现了用人为可控制因子定量控制模型冰物理和力学参数的目的 相似文献
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2006年冬末春初,在德国POLARSTERN科学考察船执行南极威德尔海西北海域考察期间,调查了考察区海冰物理和海洋生物。本文观测了航线上钻取的27支海冰冰芯的组构和71个冰晶体薄片;分析得到393组冰温数据;348组盐度、密度数据和311组叶绿素a和脱镁叶绿素含量数据;通过302组冰内相同深度孔隙率和叶绿素a含量数据分析,发现海冰物理参数影响冰内叶绿素a含量的新证据;利用收集的雪、冰厚度数据以及环境容量制约生态平衡的规律,建立了雪、冰厚度对冰底叶绿素繁荣的影响以及;确立了南极粒状冰和柱状冰内叶绿素a上限含量同卤水体积的关系。从而表达了冰晶体对卤水排泄的效应和冰物理性质对南极春季冰底和冰-水界面叶绿素a增长的贡献。此外,还得出海冰物理性质影响冰藻,并且是南极冰区水体浮游植物繁荣的关键控制因素。 相似文献
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With improved observation methods, increased winter navigation, and increased awareness of the climate and environmental changes, research on the Baltic Sea ice conditions has become increasingly active. Sea ice has been recognized as a sensitive indicator for changes in climate. Although the inter-annual variability in the ice conditions is large, a change towards milder ice winters has been detected from the time series of the maximum annual extent of sea ice and the length of the ice season. On the basis of the ice extent, the shift towards a warmer climate took place in the latter half of the 19th century. On the other hand, data on the ice thickness, which are mostly limited to the land-fast ice zone, basically do not show clear trends during the 20th century, except that during the last 20 years the thickness of land-fast ice has decreased. Due to difficulties in measuring the pack-ice thickness, the total mass of sea ice in the Baltic Sea is, however, still poorly known. The ice extent and length of the ice season depend on the indices of the Arctic Oscillation and North Atlantic Oscillation. Sea ice dynamics, thermodynamics, structure, and properties strongly interact with each other, as well as with the atmosphere and the sea. The surface conditions over the ice-covered Baltic Sea show high spatial variability, which cannot be described by two surface types (such as ice and open water) only. The variability is strongly reflected to the radiative and turbulent surface fluxes. The Baltic Sea has served as a testbed for several developments in the theory of sea ice dynamics. Experiences with advanced models have increased our understanding on sea ice dynamics, which depends on the ice thickness distribution, and in turn redistributes the ice thickness. During the latest decade, advance has been made in studies on sea ice structure, surface albedo, penetration of solar radiation, sub-surface melting, and formation of superimposed ice and snow ice. A high vertical resolution has been found as a prerequisite to successfully model thermodynamic processes during the spring melt period. A few observations have demonstrated how the river discharge and ice melt affect the stratification of the oceanic boundary layer below the ice and the oceanic heat flux to the ice bottom. In general, process studies on ice–ocean interaction have been rare. In the future, increasingly multidisciplinary studies are needed with close links between sea ice physics, geochemistry and biology. 相似文献
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New dynamics parameterizations in Version 5 of the Los Alamos Sea Ice Model, CICE, feature an anisotropic rheology and variable drag coefficients. This study investigates their effect on Arctic sea ice volume and age simulations, along with the effects of several pre-existing model options: a parameter that represents the mean cumulative area of ice participating in ridging, the resolution of the ice thickness distribution, and the resolution of the vertical temperature and salinity profiles.By increasing shear stress between floes, the anisotropic rheology slows the ice motion, producing a thicker, older ice pack. The inclusion of variable drag coefficients, which depend on modeled roughness elements such as deformed ice and melt pond edges, leads to thinner ice and a more realistic simulation of sea ice age. Several feedback processes act to enhance differences among the runs. Notably, if less open water is produced mechanically through ice deformational processes, the simulated ice thins relative to runs with more mechanically produced open water. Thermodynamic processes can have opposing effects on ice age and volume; for instance, growth of new ice increases the volume while decreasing the age of the pack. Therefore, age data provides additional information useful for differentiating among process parameterization effects and sensitivities to other model parameters.Resolution of thicker ice types is crucial for proper modeling of sea ice volume, because the volume of ice in the thicker ice categories determines the total ice volume. Model thickness categories tend to focus resolution for thinner ice; this paper demonstrates that 5 ice thickness categories are not enough to accurately resolve the ice thickness distribution for simulations of ice volume. 相似文献
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本文详细介绍了SIS海冰模式中引进两种盐度参数化方案即等盐度方案和盐度廓线方案对海冰模拟所存在的差异。利用盐度廓线方案导出的表征盐度与海冰温度间关系的方程比等盐度方案多出一项,将定义为盐度差异项。盐度差异项对海冰厚度的热力作用表现为：在海冰厚度增长季节（11月到次年5月）,盐度差异项通过升高海冰内部温度,抑制海冰增长;在消融的第一阶段（6．8月）,盐度差异项通过升高海冰内部温度加快海冰消融;在消融的第二阶段（9．10月）,盐度差异项通过降低海冰内部的温度抑制海冰消融。但尺度分析表明,盐度差异项要比方程中队海冰温度作用最大项小1．2个量级,如果采用一级近似,可以略去盐度差异项,因此盐度差异项对海冰增长和消融影响很小。同时利用冰洋耦合模式（ModularOceanModel,MOM4）,分别采用两种盐度参数化方案模拟北极海冰厚度和海冰密集度的季节性变化,模拟结果也表明两种方案模拟得到的海冰厚度和海冰密集度的季节性变化相差甚小。 相似文献
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基于非线性有限元分析方法和LS-DYNA计算软件,使用黏聚单元法建立层冰的数值模型,并进行了层冰与锥形立柱相互作用的数值模拟,研究抗冰锥角、冰厚等参数对立柱所受冰载荷的影响。模拟结果与实测和试验结果吻合良好。研究结果表明:使用黏聚单元法建立的层冰模型可以较好地模拟出层冰的破碎和堆积过程,冰载荷计算结果与ISO冰力标准结果以及离散单元法计算结果吻合较好;锥形立柱的抗冰锥角大小对冰载荷影响明显,随着锥角增大,水平方向的最大冰力增大而竖直方向上最大冰力减小;锥形结构改变了碰撞过程中层冰的破坏形式;结构物所受冰力大小与层冰厚度呈正相关,且增加速度接近线性。 相似文献
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基于黏聚单元法的抗冰海洋平台与层冰相互作用数值模拟 总被引：1，自引：1，他引：0
通过商业有限元软件LS-DYNA采用黏聚单元法模拟层冰的断裂问题,在IIHR冰池模型试验相同缩尺比参数下对KULLUK抗冰平台受到的冰力进行数值计算,探究冰厚与冰速等冰况参数对平台冰力的影响。计算结果表明,在极地作业平台主要遭遇北极海域冰况范围下,相同冰厚情况时冰速变化对倒锥形结构平台的横向冰力影响不大,而同冰速时冰力随着冰厚的增加接近线性增加。同时将计算所得结果与同条件下IIHR冰池模型试验数据、ARCTEC、ACL非冻结模型冰试验数据、实船数据和通过ISO19906规范中提供的针对大锥面结构受到层冰冰力的经验公式计算所得数据等进行了对比,验证了选用冰参数的可靠性以及该数值模型在模拟大尺度宽锥形平台遭受层冰作用问题中的适用性。 相似文献
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对海冰的运动规律进行精确、连续和长周期的实时监测有助于海冰热力学和动力学的研究,也可保障冰区生产活动的安全进行。针对辽东湾海冰的运动特点和工程需求,在JZ20-2油气平台上建立了海冰雷达监测系统。采用数字图像处理技术对海冰雷达监测图像进行了分析和软件开发,可对海冰密集度、速度和冰块面积等海冰参数进行提取。采用该海冰雷达监测系统和数字图像处理软件,在2011-2012年冬季对该海域的海冰运动规律进行了全冰期的连续监测,在此基础上重点对海冰速度的雷达图像监测结果进行了分析,讨论了海冰速度场分布以及连续48 h的变化过程。以上结果为海冰的生消运移规律研究和油气作业区的海冰管理工作提供了可靠的现场监测数据。对海冰雷达现场监测及数字图像处理中的问题及改进方法进行了讨论。 相似文献
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冰脊对极地船舶及海洋工程结构的冰载荷设计及冰区安全运行具有重要的影响,其几何形态是重要的考虑因素。为研究冰脊的几何形态,本文基于Voronoi切割算法构造扩展多面体海冰单元,并使其相互冻结形成平整冰;采用离散单元法模拟海冰在相对运动时挤压形成冰脊的动力过程,统计分析脊帆高度、龙骨宽度、龙骨深度、龙骨水平倾角等主要几何参数,并确定这些几何参数间的对应关系。将离散元模拟结果同冰脊现场观测资料对比分析以验证扩展多面体离散元方法模拟冰脊形成过程的可行性。在此基础上讨论冰厚、冰速、海冰强度等因素对冰脊形态的影响。本文采用离散元方法对冰脊形成过程及几何特性的数值分析可为深入开展冰脊的形成机理及其对船舶、海洋工程结构物的冰载荷分析提供参考依据。 相似文献
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Three types of ice loading, which are most commonly present when ice acts on structures, are chosen and simulated for use of fatigue crack propagation tests on offshore structural steel A131. The three types of ice categorized in accordance with the failure modes when acting on structures called crushing ice, bending ice, and buckling ice, respectively. This paper presents an experimental investigation on the fatigue crack propagation behavior of widely used high strength steel A131 for offshore jackets in the loading environment of ice crushing, bending, and buckling. The test results of fatigue crack propagation in steel A131 under these simulated ice loading at temperature 292K. are presented and analyzed in detail in this paper. The amplitude root mean square stress intensity factor is optimized to be the fundamental parameter of fatigue crack propagation for all types of ice loading histories. The results are also compared with constant amplitude fatigue crack propagation conclusions as in wave loa 相似文献
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海冰在结构前的破坏模式以及产生的冰载荷与结构尺度和海冰厚度密切相关。采用海冰离散元方法（DEM）模拟平整冰与直立结构相互作用过程中的海冰破坏模式及整体冰载荷。该离散元方法的计算参数通过与Norstr?msgrund灯塔的现场实测数据对比进行了可靠性验证。在此基础上,对不同宽厚比（结构宽度与海冰厚度的比值）工况下平整冰与直立结构作用过程中的海冰破坏模式和整体冰压力进行了离散元分析。模拟结果表明：当宽厚比＜10时,海冰破坏模式主要为挤压破坏;当10≤宽厚比＜30时,海冰混合破坏发生;当宽厚比≥30时,海冰屈曲破坏发生。从海冰断裂长度与平均冰压力两个方面进一步说明了海冰破坏模式的转变过程。最后,构建了直立结构极值冰压力计算公式。研究成果可为寒区直立结构的整体设计提供参考。 相似文献
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作用于平台桩腿的海冰屈曲破坏冰压力随机过程模型及其参数确定 总被引：2，自引：1，他引：2
冰对结构的作用过程是典型的随机过程。本文在冰压力过程为平稳过程的假设下，从渤海海冰对平台桩腿作用的大量实测冰压力数据中，选取了２１条冰屈曲破坏时的冰压力时程曲线，对它们进行谱分析后，得到了单点冰屈曲破坏的压力随机过程的谱密度，并确定了谱参数及其跟环境要素的关系，依据文献［１］中冰压力沿圆柱面的空间分布，建立了绕桩腿的冰压力随机场模型，并得到了作用于桩腿的总冰力随机过程及其谱密度。本文的研究成果为平台结构冰激随机振动和疲劳累积损伤分析提供了荷载基础 相似文献
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Sea ice drift is mainly controlled by ocean currents, local wind, and internal ice stress. Information on sea ice motion, especially in situ synchronous observation of an ice velocity, a current velocity, and a wind speed, is of great significance to identify ice drift characteristics. A sea ice substitute, the so-called "modelled ice", which is made by polypropylene material with a density similar to Bohai Sea ice, is used to complete a free drift experiment in the open sea. The trajectories of isolated modelled ice, currents and wind in the Bohai Sea during non-frozen and frozen periods are obtained. The results show that the currents play a major role while the wind plays a minor role in the free drift of isolated modelled ice when the wind is mild in the Bohai Sea. The modelled ice drift is significantly affected by the ocean current and wind based on the ice–current–wind relationship established by a multiple linear regression. The modelled ice velocity calculated by the multiple linear regression is close to that of the in situ observation, the magnitude of the error between the calculated and observed ice velocities is less than12.05%, and the velocity direction error is less than 6.21°. Thus, the ice velocity can be estimated based on the observed current velocity and wind speed when the in situ observed ice velocity is missing. And the modelled ice of same thickness with a smaller density is more sensitive to the current velocity and the wind speed changes. In addition, the modelled ice drift characteristics are shown to be close to those of the real sea ice, which indicates that the modelled ice can be used as a good substitute of real ice for in situ observation of the free ice drift in the open sea, which helps solve time availability, safety and logistics problems related to in situ observation on real ice. 相似文献
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