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锥体导管架海洋平台冰激振动的DEM-FEM耦合分析及高性能算法 总被引：1，自引：0，他引：1
在寒区海域,冰荷载是影响海洋平台安全运行的主要环境荷载之一,由其引起的冰激振动给平台结构及其上部设备带来了严重危害。为分析不同冰况下平台的振动响应,本文建立了导管架海洋平台冰激振动的离散元（DEM）-有限元（FEM）耦合模型。采用具有黏接-破碎性能的等粒径球体离散单元对海冰的破碎特性进行模拟,通过由梁单元构建的海洋平台有限元模型获得结构的振动响应。在离散元与有限元的接触区域中实现了两个模型间计算参数的传递。为提高该耦合模型的计算效率和规模,发展了基于动力子结构方法的DEM-FEM耦合模型。为验证该耦合模型的有效性和可行性,将不同冰况下得到的冰荷载与ISO19906和JTS 144-1-2010标准进行了对比。结果表明,计算得到的冰荷载与标准相近,且冰厚与冰荷载呈二次非线性关系。同时,从冰速和冰厚两方面对比了渤海四桩腿JZ20-2 MUQ锥体导管架平台冰激振动加速度的数值结果和现场实测数据,发现冰速与振动加速度呈线性关系,冰厚与振动加速度呈二次非线性关系,并且振动加速度与冰速和冰厚平方的乘积呈线性关系。 相似文献
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应用ANSYS软件建立了平台和冰相互作用的有限元模型,构建了自升式平台的冰激振动模型,并计算基于2种冰力模型的自升式平台的动力响应。此动力分析方法具有建模方便和计算精度高的特点。以某自升式平台为例,计算了冰和平台结构相互作用的耦合效应,为自升式平台冰激振动安全评估提供了参考依据。 相似文献
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自升式钻井平台在设计时通常不考虑冰荷载的作用,要实现冰区作业,首先需要对该类平台的抗冰能力进行准确评估。本文通过开展冰池试验,对自升式钻井平台冰载荷作用机理、结构冰激特性以及抗冰方法等进行研究。海洋结构受到的冰荷载大小以及结构响应值与冰厚密切相关,冰激振动机理与冰厚无关,探究不同冰速和冰厚下冰荷载及振动响应的时程曲线,可发现低冰速下结构展现出的准静态响应特征以及高冰速下的随机响应特征。冰激振动的发生是结构固有特性、冰速、冰厚、冰材料参数等因素共同影响的结果,其作用机理尤为复杂,本研究侧重于桁架式自升式平台冰区作业中结构冰激振动特性研究。 相似文献
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针对渤海湾某风电场的海上固定式风机支撑结构,采用适用于大直径单桩结构的PSI曲线模拟桩土相互作用,并采用SACS软件建立支撑结构的动力分析模型。首先对支撑结构进行模态分析;其次考虑海冰结构的随机振动作用模式,根据适用于渤海湾的随机冰力谱构造随机冰载荷时程曲线,基于半耦合的时域方法,采用SACS软件对支撑结构进行冰激振动分析,输出塔筒顶部加速度、单桩基底剪力及倾覆力矩等响应参数的时程曲线和响应功率谱;最后针对冰厚、冰速和海冰强度等海冰参数对支撑结构的冰激振动进行敏感性分析。研究结果表明,在随机振动模式下,冰载荷及结构动力响应对冰厚和海冰强度较为敏感,在进行冰激振动分析时应合理确定冰厚和海冰强度等参数。 相似文献
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导管架平台安装锥体降低冰振效果研究 总被引：1，自引：0，他引：1
冰荷载是寒区海洋结构的控制荷载.在圆柱结构上安装锥体用以降低极值冰力,这一概念已得到理论与模型实验的验证,但是安装锥体对降低结构冰激振动的效果还没有得到充分论证.首先分析和比较了圆柱结构和加锥结构的交变冰力与冰振响应形式.基于现场原型监测系统的实测数据,无论是圆柱结构和加锥结构都能发生强烈的冰激振动,圆柱结构上的稳态冰激振动最为严重.通过一座单腿圆柱结构加装锥体前后的冰振响应监测和分析,得到安装破冰锥体对降低冰振的实际效果.理论分析和实测数据表明,破冰锥体从根本上避免了冰激结构稳态振动的发生. 相似文献
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一种冰-海洋模式的热力耦合方案 总被引：4，自引：1，他引：3
冰与海洋的热力耦合对冰与海洋环流的模拟有极其重要的影响,是冰-海洋相互作用的一个重要方面.对其精确确定需要详细考虑冰-海洋界面附近的湍流过程,这在长时期的模拟特别是气候模拟中,常受到技术条件的限制.过去的研究常常假设冰下海洋混合层的温度为冰点,特别是在单纯冰模式的模拟中,但考虑海冰漂移和冰点变化的效应时,这一假设是不精确的.因此,弱化冰下海洋混合层温度为冰点的约束,不考虑详细的冰-海洋界面和海洋混合层的湍流过程,根据冰-海洋耦合系统的能量收支关系,设计了一个简化的冰-海洋热力耦合方案.对该方案引起的海洋混合层适应、热力结构和海冰发展的影响进行了分析,并将其用于全球冰海洋耦合模式的数值试验,结果表明,在大气热力强迫下该耦合方案既可使冰区混合层海水温度向冰点适应,又使冰边缘带海水温度与冰点保持明显差异,能够较好地反映冰-海洋热力相互作用.利用该耦合方案构造的全球冰-海洋耦合模式模拟的海冰范围及季节变化与实际观测非常接近. 相似文献
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冰激锥体振动物理模拟实验 总被引：3，自引：0，他引：3
应用DUT 1非冻结可破碎模型冰进行冰激锥体振动模拟实验的实验设备和模型的设计 ,给出了低冰速和高冰速两种情况下的结构位移曲线、冰力曲线及其幅值谱分析结果 ,得出了结构卓越频率和冰速与特征长度之比的关系 ,发现冰激锥体振动同冰激柱体振动一样有“频率锁定”现象。将实验结果与已有的冰排与圆柱相互作用实验结果进行比较 ,发现冰激锥体振动和冰激柱体振动有着相似的机理 相似文献
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冰激结构振动的非线性分析 总被引：3，自引：1，他引：3
冰对结构的作用表现为冰的变形和破碎两个阶段,具有间隙非线性特性.考虑到这个特性,我们利用非线性分析方法建立了非线性的冰-结构相互作用的动力学模型,从理论上阐明,冰激柔性结构的振动是一种多频干扰、自激和强迫的耦合振动系统,并研究了试验中观察到的锁频现象的机理.本文得到的冰力计算公式可用于海洋工程结构的设计计算. 相似文献
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冰激振动及冰荷载动力特性的试验研究 总被引：2，自引：0，他引：2
回顾了解决海冰引起结构振动分析方法的要求，通过室内冰力模型试验得出了冰激振动的重要参数－冰力频率，幅值的特性。研究表明，在低冰速时，冰力频率与冰速对冰厚之比呈线性关系；高冰速时，冰力步与冰速对冰厚之比呈现恒定性，文章还根据试验数据以及统计分析，推荐了冰力幅值计算公式和取值范围。 相似文献
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Arne Schnack-Friedrichsen Angela M. Davis Jim D. Bennell Dei G. Huws 《Marine Georesources & Geotechnology》2001,19(4):221-243
The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths. 相似文献
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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。 相似文献
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Shigehisa Nakamura 《Marine Geodesy》2000,23(1):55-61
Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone. 相似文献
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The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics. 相似文献
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《海洋学报(英文版)》2014,(9):F0003-F0003
<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology, 相似文献
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Phylogenetic diversity and phenotypic characterization of cultivable bacterioplankton isolated from polar oceans 总被引：1，自引：0，他引：1
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. 相似文献
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The relationship between the flux of exotic benthic foraminiferal tests (i.e. tests which are supplied from open-sea sources alone) in a tidal inlet and that of bulk sediment was analysed, which can be expressed as two first-order linear equations. According to this relationship, in order to determine net sediment transport directions in the entrance, the test concentration in surficial sediments of the tidal basin can be compared against a ‘ critical level ’. The critical level is determined for the conditions that no net transport of bulk sediment is present within the entrance. If the observed concentration (averaged over the tidal basin) is higher than the simulated critical level, then the net sediment transport is directed to landward. This method is applied to the analysis of net sand transport at Christchurch Harbour, a tidal inlet system located in southern England. In this investigation, concentrations of exotic foraminiferal tests in the surficial sediments of the tidal basin and ebb tidal delta area were obtained from the analysis of sea-bed sediment samples. A series of probable critical levels were calculated based upon the data sets with regard to: (1) sediment discharge from the rivers; (2) magnitude of sediment discharge within the entrance during the ebb; (3) the test concentration outside the harbour; (4) the thickness of the moving layer; and (5) two parameters associated with dispersive processes. The results show that the concentration in the tidal basin sediment is higher than a number of simulated critical concentrations for representative cases. Consequently, the high level of the concentration of exotic benthic foraminiferal tests within the harbour should be explained as a result of landward net transport of sands within the entrance. 相似文献