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在浅水海域,采用单层保温管结构代替双重钢管保温结构具有很好的发展应用前景,但在单层管的铺设过程中管线各层之间和保温层内将产生较大的剪应力,如何防止各层间的错动和保温层材料的剪切破坏是设计所必须解决的两个主要问题。以渤海某油田海底管线建设项目为例,根据单层保温管的结构特点,力的层间传递特性和变形协调条件,建立了单层保温管各层层间剪切力和保温层中剪应力的计算方法,为海底单层保温管的设计提供了依据。 相似文献
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基于粒子图像测速技术(PIV)对小间距比比L/D=1.5工况下方形布置四圆柱在不同来流角角α(α=0°、15°、30°、45°)条件下的尾流流场特性进行了试验研究,分析了不同来流角度条件下四圆柱瞬时和时均尾流流场特征,获得了瞬时和时均速度矢量、涡量等值线、流线拓扑及雷诺应力分布随来流角度变化的规律。试验结果表明,来流角度对方形布置四圆柱尾流形态有显著影响。四圆柱瞬时尾流形态随来流角度增大可分为延伸体流动流态(α=0°)、尾流剪切层附着流态(α=15°、30°)及尾流剪切层共同脱落流态(α=45°)三种流态。当来流角度增大时,四圆柱下游断面平均流向速度分布由"W"形向"U"形转变,时均雷诺正应力及雷诺剪切应力等值线分布特征也会发生明显改变。 相似文献
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简要回顾了潮汐河口环流、湍流、混合与层化的基本物理概念、内涵、研究方法、研究成果,指出了主要的研究进展,最后,展望了今后的研究方向。本文不考虑悬沙和风浪的影响。经典的河口环流也因潮汐应变的出现而受到挑战,河口环流由重力环流和潮汐应变环流构成。"涡黏度-剪切协方差(ESCO)"概念的提出,又区分出重力ESCO环流与潮汐ESCO环流。横向环流,尤其具有曲率的弯道中的横向环流,也得到进一步的理解。涡度方法的应用,揭示横向环流不仅由各种不同物理机制造成,而且对纵向河口重力环流有重要的影响。分层流中剪切湍流的理论加深了人们对潮汐河口湍流、混合的物理学的认识,势能差异方程更是使得定量理解潮汐河口混合与层化的三维时间、空间变化成为可能。 相似文献
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黏性泥沙在黄河水下三角洲广泛分布,其在外部载荷作用下易引发泥沙淤积、冲刷、海床流化等问题,对港口、航道、海底管线等工程设施构成巨大威胁。利用黄河水下三角洲埕岛海域所取海底表层沉积物,制备不同固结时间和不同含水率的高浓度黏性泥沙样品。采用R/S流变仪,对所制备高浓度黏性泥沙样品进行全剪切速率下的流变试验,分析黄河水下三角洲高浓度黏性泥沙流变特性及含水率和固结时间对流变特性的影响。结果表明,高浓度黏性泥沙在剪切荷载作用下流化失稳,发生相态转化;屈服应力在固结120 min后增加了35%;含水率50%以上高浓度黏性泥沙在高剪切速率下表现出剪切增稠行为,且随含水率增加剪切增稠行为越明显;Power模型适用于含水率大于50%的高浓度黏性泥沙在高剪切速率下的流变行为。本研究可为海底黏性泥沙运动过程数值模拟与海底重力流等灾害预测提供参考。 相似文献
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我国近海海底有超过3 000km的输油气管线,定期对海底输油气管线进行检测是保障海底输油气管线安全和海洋环境安全的重要手段。为保护海洋环境和海底油气管线安全,对广东近海某段海底输油气管线进行了安全检测,采用浅层剖面测量、侧扫声呐测量和多波束测量手段,对管线路由区域进行了勘测。勘测结果表明:检测区域油气管线路由没有裸露和悬空,路由周边地层较稳定,根据侧扫声呐和多波束测量结果,发现在路由区海底存在影响管道安全的因素,路由区海底拖锚等痕迹较多,距离路由大约950m处有人工采沙坑存在。建议相关部门对该区域应加以重视,加大海上巡逻执法力度,加强宣传工作,增强大众的海底管道保护意识。 相似文献
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细长海洋立管在复杂来流作用下的涡激振动（VIV）是海洋工程领域备受关注的热点问题。采用双向流—固耦合方法,对立管在指数剪切来流作用下的涡激振动实施了数值仿真研究。基于均方根振幅包络图的显性模态分析发现,与线性剪切流工况相比,当流速较小时,立管模型在指数剪切流作用下振幅最大值相对较小;流速较大时,指数剪切流的非线性分布致使立管的振动响应增强。通过对立管模型均方根振幅包络峰、谷处的振动响应频率分析发现,在波峰位置处振动频率单一且较为稳定,而在相邻波谷位置处多频共存现象显著,两者有显著差异。沿管的轴向波形主要表现为驻波主导和驻波—行波混合模式,行波一般间歇发生,流速越大发生频次愈高,其在横流向的传播方向通常由高流速区段传递至低流速区段。指数剪切流作用下,沿管体轴向各截面位置处的旋涡脱落模式差异显著,高流速段尾流区的旋涡发放具有较强的周期性,涡管完整且与管轴存在一定偏离角度,低流速段蜂窝状离散涡旋较多。 相似文献
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采用弯曲元剪切波测试方法对在南黄海中部采集到的沉积物样品进行了剪切波速度测试,基于所获得的剪切波速度数据,分析了研究区沉积物剪切波速度特性及分布规律。分析表明,沉积物剪切波速度为12.05~74.55m/s,总体相对较低。浅表层沉积物剪切波速度呈现出分区域分布特征,可分为东北部低速区、西南部高速区、北西-南东向梯度带以及测区东南部的低速背景上的串珠状高速异常区四个区域。通过回归分析,建立了剪切波速度与密度、含水率、孔隙比、孔隙度、液限、塑限、压缩系数、抗剪强度等沉积物物理力学参数之间相互关系的经验回归公式。回归分析结果表明,海底沉积物剪切波速度与上述物理力学参数之间均具有较好的相关性,相关系数R均大于0.80。 相似文献
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- With the rapid development of the offshore oil industries, submarine oil / gas pipelines have been widely used. Under the complicated submarine environmental conditions, the dynamic characteristics of pipelines show some new features due to the existence of both internal and external flows. The paper is intended to investigate the vortex-induced vibration of the suspended pipeline span exposed to submarine steady flow. Especially, the effects of the flow inside the pipeline are taken into account. Its influences on the amplitude of pipeline response, and then on the fatigue life, are given in terms of the velocity of the internal flow. 相似文献
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The stability of submarine pipelines has been extensively studied by coastal engineers in recent years. Seismic-induced pore pressure and effective stresses in the saturated porous seabed and pipeline are the main important factors in the analysis of foundation stability around submarine pipelines. The majority research of the seismic-induced dynamic response around an offshore pipeline has been limited to two-dimension cases. In this paper, a three-dimensional finite element model including buried pipeline is established by extending DYNE3WAC. Based on the proposed numerical model, a parametric study is conducted to examine the effects of soil characteristics and pipeline configurations on the seismic-induced soil response around offshore pipelines. 相似文献
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考虑阻尼海底悬跨段管道的动力特性及允许悬空长度 总被引：8，自引：0，他引：8
以海底悬跨段输液管道为研究对象,考虑管道结构阻尼、流体附加阻尼、管内流体流动及管道轴向力和压强的作用,对其进行受力分析,导出管道振动微分方程,进而得到管道动力特性方程。用Hermit插值函数对管道的动力特性方程进行离散得到有限元表达式,采用复模态分析法,求得管道的自振频率。为防止管道发生横向涡激振动,用约化速度作为控制条件,确定管道允许悬空长度。结果表明,管道允许悬空长度随着内流流速、轴向压力和管内压强的增加而减小,随着轴向拉力的增加而加大。 相似文献
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Mechanism of local scour around submarine pipelines based on numerical simulation of turbulence model 总被引：2，自引：2，他引：0
1 IntroductionSubmarine pipelines are important ocean engi-neeringequipm ents, especiallyfortheoiland gasin-dustries. M anyresearchershavebeendedicatedtotheproblem of local scour around the submarinepipelines, butmostoftheirwork arelaboratory testsand foc… 相似文献
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内流对海底管线涡致振动与疲劳寿命的影响 总被引：2，自引：0，他引：2
在复杂的海洋环境条件下，管道的动力学特性受到内外部流体的作用而呈现出新的特点。本文通过对处在海底平稳流动作用下的悬跨管道的涡致振动进行分析，特别地考虑到管道内部流动的作用，给出了内流速度对管道响应幅度的影响，进而指出其对管道疲劳的意义。 相似文献
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考虑流固耦合时的海底管道悬跨段非线性动力分析 总被引：6，自引：0，他引：6
通过对管道的涡激振动试验,提出了考虑流固耦合的非线性涡激升力表达式,并用该式进行了海底管线悬跨段非线性动力响应时程分析。对考虑流固耦合与未考虑流固耦合情况下得到的管道动力响应时程进行对比,算例表明:当管外流场流速与管道顺流向振动速度值较接近时,不考虑流固耦合时的计算结果明显小于考虑流固耦合时的计算结果。分析认为,在管外流场流速与管道顺流向振动速度值较接近的情况下,管道的涡激振动计算宜采用非线性涡激力模型。 相似文献
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Jingbo Su Jianfeng Li Ruihu Zhu Wanggen Qin Qiu Zhai 《Marine Georesources & Geotechnology》2016,34(7):689-702
To assess the impact of pile driving on adjacent submarine pipelines during the reconstruction of a pier berth, the local damage model of submarine pipelines is established to explore the safety thresholds of the particle peak velocity and horizontal displacement. The results are analyzed and adjusted by the existing standards and the corresponding literatures. Then, a three-dimensional numerical model is presented to assess the feasibility of the construction of piles by the obtained safety limits, in which the nonlinear behavior of the soil and stress–seepage coupling analysis are considered. After the construction, the safety of submarine pipelines is rechecked by the measured value of the particle peak velocity and horizontal displacement. Meanwhile, the propagation law of vibration, the horizontal displacement of underground soil, and the pore pressure during pile driving are explored. The results indicate that the construction of piles of 2# mooring pier did not cause damage to adjacent submarine pipelines. However, the construction of piles of 1# mooring pier which is nearer may cause damage to submarine pipelines. 相似文献
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研究旨在提出波流联合作用下海底管道侧向运动数值模拟分析方法。通过建立三维离散刚体模拟海床,梁单元模拟海底管道,设置了两个载荷步模拟管道与土壤接触的过程,解决了实体模型不易收敛的问题。分析了不同管—土法向行为接触刚度、不同管—土切向行为摩擦系数、不同波流参数以及不同单位长度管道水下质量对海底管道侧向运动的影响。研究表明：海底管道的最大等效应力、最大侧向位移、最大接触压力以及最大横向摩擦剪应力对于管—土法向行为接触刚度的变化并不敏感;管道的最大侧向位移随着管—土切向行为摩擦系数增大而减小,呈现出线性变化的关系;当波高一定时,管道的最大侧向位移随着流速的增加而增大,并且波高越小,最大侧向位移随流速增加的速度明显越大;管道最大侧向位移随着单位长度管道水下质量的增加而减小,并且呈现出线性变化的关系。 相似文献
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Submarine pipelines that transport crude oil and natural gas are often in a complex marine geological environment and may become unstable and fail upon impact by submarine landslides. Previous research has mostly focused on the impact forces exerted by submarine landslides on suspended pipelines, but the impact of submarine landslides on pipelines laid on the seafloor at various impact angles, θ, have been relatively infrequently discussed, and the effects of suspended height, H, on the impact forces exerted by submarine landslides on pipelines have not been thoroughly investigated. In this study, based on the Herschel–Bulkley model, the impact forces exerted by a submarine landslide on laid-on or suspended pipelines at various impact angles θ were simulated using the computational fluid dynamics (CFD) approach. Equations for calculating the axial and normal drag coefficients of a submarine pipeline were proposed. The CFD numerical simulation results were rearranged based on the soil mechanics approach. By comparing the parameters, an essentially corresponding relationship was found between the soil mechanics and CFD approaches when the equations were used to calculate the impact forces exerted by a submarine landslide on a pipeline. In addition, a semi-analytical expression for the failure envelope was provided. Furthermore, the effects of H on the forces on a pipeline were discussed, and an equation for calculating the acting forces on a pipeline along the flow direction of a submarine landslide that comprehensively accounts for the effects of θ and H was proposed. The lift force was discussed preliminarily and the results provide a basis for further investigation. The achievement of this study is applicable for selecting locations of submarine pipeline routes and for designing submarine pipelines. 相似文献
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Li Yucheng Zhang Ningchuan
Professor Dalian University of Technology Dalian . Lecturere Delian University of Technology Dalian 《中国海洋工程》1994,(1)
- A composite pipeline is defined as a main big pipe composed of one or several small pipes. The flow behaviour around a submarine composite pipeline is more complicated than that around a single submarine pipeline. A series model test of composite pipelines in a wave-current coexisting field was conducted by the authors. Both in-line and lift forces were measured, and the resultant forces were also analyzed. The results of lift forces and resultant forces are reported in this paper. It is found that the lift force coefficients for composite pipelines are well related to the KC number. The lift force coefficients for an irregular wave-current coexisting field are smaller than those for a regular wave-current coexisting field. The frequency of lift force is usually twice the wave frequency or higher. The authors test indicates that the resultant forces are about 10 to 20 percent larger than in-line forces (horizontal forces). The effect of water depth is analyzed. Finally, the relationship between lift f 相似文献