共查询到19条相似文献，搜索用时 78 毫秒
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为了研究毛发长度和毛发密度对毛发缆减阻性能的影响，设计并进行了水池试验。通过研究6种不同毛发长度、不同毛发密度拖缆的阻力系数随航速的变化，找到减阻效果最优的缆型，得到最佳缆型的减阻率。结果显示：在相同的迎流角下，圆缆的阻力系数在1~1.1左右，毛发缆的阻力系数随速度变化不明显；在毛发长度为9~11倍拖缆直径、毛发密度为60根/m时，毛发缆的减阻效果最优，减阻率可达20%。验证了毛发缆具有很好的减阻性能，为大深度拖曳系统的缆型设计提供了参考依据。 相似文献
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为了深入研究亚临界雷诺数下光滑和沟槽圆柱绕流阻力及流场特性。采用SSTk-w模型对雷诺数Re分别为2×104,6×104,1×105和1.4×105的光滑圆柱和V型沟槽圆柱绕流进行三维流场数值模拟,首先以光滑圆柱绕流为算例与相关实验研究结果进行了对比,验证了SSTk-w方法的准确性,然后在不同雷诺数条件下,开展了V型沟槽圆柱绕流数值模拟研究;与光滑圆柱相比,V型沟槽圆柱具有较好的减阻效果,最大减阻率达28.4%;在相同雷诺数下,沟槽圆柱表面边界层分离点与光滑圆柱表面分离点相比更靠后。V型沟槽织构可有效改变尾流区旋涡脱落频率和尾流区湍流的发展,为隔水管减阻和提高隔水管柱系统的稳定性提供参考。 相似文献
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为了研究沟槽圆柱在亚临界雷诺数下的阻力特性,采用数值模拟与水槽试验相结合的方法,对沟槽圆柱的减阻性能进行研究.开展三维流场数值模拟,确定最佳仿真模型参数,研究沟槽参数、雷诺数以及迎流角对减阻效果的影响,设计了一种减小端面绕流干扰的水槽试验,验证仿真结果.结果表明:在雷诺数为40000时,沟槽深度为0.0075D(D为圆... 相似文献
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近年来微气泡减阻技术应用于水面舰船的相关研究取得重要进展，许多舰船已经采用了此类技术。然而该技术在潜航器上的应用整体上仍处于理论分析和试验测试阶段。以回转体潜航器简化模型为研究对象，利用多孔介质来简化喷气小孔，并结合不可压缩水体和可压缩理想气体的流体体积（VOF）方法，建立了Realizable ε-k湍流计算模式。通过拖曳试验验证了多孔介质等效喷气小孔的合理性和数值模式的准确性，结合试验和数值结果探究了微气泡减阻技术对潜航器航行阻力的影响。数值结果显示，气泡对潜航器尾流低速区的改变使尾部压力分布产生变化从而导致压差阻力增高。同时气泡可以显著降低其覆盖区域的黏性阻力。并且随着来流速度的提高，气泡覆盖范围扩大，黏性减阻率持续增加。进一步地，建立了加长改进模型，数值模拟结果表明，微气泡减阻技术不仅能大幅减小黏性阻力，还能有效减小模型总阻力。 相似文献
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海底管道是海洋油气输送的重要纽带。为解决海底管道面临的水合物生成和堵塞问题,文章结合海底多相流管道水合物生成的数学模型,采用OLGA对海底管道不同含水率、气油比和流量下水合物的生成情况进行数值模拟。研究结果表明：在某海底管道的工艺参数条件下,水合物生成风险随着含水率和流量的增大而降低,随着气油比的增大而增加;海底水平管路和立管都有可能生成水合物,尤其立管常是水合物最大生成量的位置;模拟结果可为海底管道水合物的防治和保障海底管道的安全运行提供参考。 相似文献
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针对吸力式沉箱在黏性底床中沉贯安装的减阻问题,基于黏性泥沙的流变特性,开展了一系列不同振动荷载作用下的室内沉贯模型试验,分析了振动荷载对吸力式沉箱沉贯过程的影响和沉贯减阻效果。试验结果表明：在压力沉贯阶段或吸力沉贯阶段施加高频振动荷载,均能促使吸力式沉箱侧壁周围的土体发生流化,有效降低沉箱的沉贯阻力;减阻效果与振动频率和沉箱的长径比有关,与振动频率成正比,与沉箱的长径比成反比;存在一个临界频率,当振动频率大于该频率后,沉贯阻力随频率的减小不明显;施加高频振动荷载有助于减小吸力沉贯阶段沉箱内的土塞高度,促进沉箱沉贯到位。研究成果可为黏性泥沙流变减阻技术在吸力式沉箱中的应用提供理论依据和技术参考。 相似文献
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近壁圆柱绕流问题在海底悬跨管道的研究中具有重要的意义。在绕流阻力、升力以及海底土壤的耦合作用下,海底管道所发生的移位、悬跨等现象对于海底管道的安全运行构成了很大的威胁。正确预测各种绕流条件下管流之间的作用力是保证油气管道安全的首要任务。海底管道在极端海洋环境条件下的管、流相互作用为高雷诺数绕流问题,处于高雷诺数下的绕流模拟比处于低雷诺数下的绕流模拟要复杂很多,它需要更精细的网格以及合适的湍流模型。此文对处于悬跨状态下的海底管道进行数值研究,给出不同间隙比下海流绕流海底管道的流场结构形态,分析了间隙比对绕流阻力和绕流升力的影响,为进一步研究海底悬跨管道的受力和变形提供载荷边界数据。 相似文献
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在海洋油气开发中,水下节流阀作为水下生产系统的重要组成部分,用于调节生产单元的流量,冲蚀是其主要失效因素之一,因此研究水下节流阀冲蚀失效的影响机理尤为重要。以某笼套式角型水下节流阀为研究对象,建立了水下节流阀的三维流体域模型,采用ANSYS Fluent的标准k-ε湍流模型、DPM离散相模型和Generic冲蚀模型进行了不同开度下的流场数值模拟计算和冲蚀分析,研究了流场环境参数对冲蚀的影响。对水下节流阀流场数值模拟结果进行分析,得到了水下节流阀流场内流速、压力的分布规律。对不同开度下水下节流阀的冲蚀数值模拟结果进行分析,发现节流孔处是冲蚀最为严重区域,得到了冲蚀率随开度的变化曲线。对不同流场环境参数下水下节流阀的冲蚀数值模拟结果进行分析,得到了最大冲蚀率和最大冲蚀深度随流场环境参数的变化规律。根据数值模拟的分析及结论可以对水下节流阀结构进行改进,并在油气生产中对流场环境参数进行控制,提高海洋油气开发的经济效益。 相似文献
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该文研究了海洋平台输液管道振动流的行为特性。依据振荡流体力学基本原理 ,建立了输液管道非定常、不可压缩、粘性振动流的物理模型和数学模型。推导出了关于流场速度、压力系数的微分方程组 ,得到了不同条件下流动的速度和压力分布。结果表明流体诱发的海洋平台输液管道振动流的行为特性受管道结构形状及流体性质的影响。比较等截面管道的变分解和数值解 ,说明本文所选用的方法用于研究海洋平台输液管道振动流是有效的。 相似文献
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To obtain a better understanding of the oscillatory soil liquefaction around an offshore pipeline, a three-dimensional integrated model for the wave–seabed–pipeline interaction (WSPI) is proposed by combining the Reynolds-Averaged Navier–Stokes equations for flow simulations and the dynamic Biot’s equation (“u-p” approximation) for the poro-elastic seabed model. Compared with previous investigations, the wave–current interaction is included in the present WSPI system. At a given time step, the wave pressure extracted from the flow model is applied on the seabed surface to determine the corresponding oscillatory seabed response around an offshore pipeline. The integrated numerical model is first validated using previous laboratory experiments. Then, a parametric study is conducted to examine the effects of flow obliquity and pipeline burial depth on the soil response around an offshore pipeline. Numerical results indicate that the soil under the pipeline is more susceptible to liquefaction at a reduced flow obliquity and pipeline burial depth. Moreover, the liquefaction depth in the case where the wave travels along the current can increase by 10%–30% compared to that in the case where the wave travels against the current, when the magnitude of the current velocity is 1 m/s. 相似文献
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埕岛油田海底管道安装应力计算方法的研究及应用 总被引：1，自引：0，他引：1
海底管道的施工质量直接关系到海底管道能否长久地安全运行。对施工期间各种环境荷载、施工荷载作用下的海底管道在力和变形进行计算,分析和监控、是确保底管道施工质量的不可缺少的重要手段。本文通过计算实例对浮拖法敷设海底管道安装计算分析的方法作了研究,并对胜利海洋石油开发公司与天津大学合作研究开发的涨底管道安装分析软件在胜利岛油田海底管道工程建设中的应用作了介绍。 相似文献
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A numerical model is developed to predict the onset of local scour below offshore pipelines in steady currents and waves. The scour is assumed to start when the pressure gradient underneath the pipeline exceeds the floatation gradient of the sediments. In this model, the water flow field above the bed is determined by solving the two-dimensional (2-D) Reynolds-averaged Navier–Stokes equations with a k-ω turbulence closure. The seepage flow below the seabed is calculated by solving the Darcy's law (Laplace's equation) with known pressure distribution along the common boundaries of the flow domains-seabed. The numerical method used for both the turbulent flow around the pipeline and Darcy's flow in the seabed is a fractional finite element method. The average pressure gradient along the buried pipe surface is employed in the evaluation of onset condition with a calibration coefficient. The numerical model is validated against experimental data available in literature. A unified onset condition for steady currents and waves is proposed. Influences of flow parameters, including water depth, embedment depth, boundary layer thickness, Reynolds number (Re) and Keuleagan–Carpenter (KC) number, on the pressure drop coefficient over the pipeline are studied systematically. 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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简要介绍了国内浅海油田的发展现状和胜利浅海油田采用“卫星平台—海底管线—中心平台—海底管线—陆上联合站”的生产运行开发模式,以及国外管道维修技术和装备的手段。重点介绍了一种能潜入海底自动探测跟踪和准确定位坐底、对管线进行维修的水下装置,它在结构型式、操作控制定位方式、管线探测跟踪、维修手段等方面有独到之处。 相似文献
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The spoiler is a kind of device to disturb current and promote burying.At present,all submarine pipeline spoilers at home and abroad are parallel spoilers,that is,the plane of the spoiler is parallel to the vertical plane of the pipeline axis.According to the results of indoor experiments,when the pipeline with the forward spoiler is installed perpendicular to the direction of water flow,the spoiler will accelerate the seabed erosion and cause the pipeline to endure downward pressure,which will eventually cause the pipeline self-buried to form a protection.However,when the pipeline direction is consistent with the flow direction,the self-buried behavior and protective effect is vanished.By aiming at the defect that the forward spoiler cannot be self-buried when the direction of the pipeline and the flow are basically parallel,the spoiler burying aid device perpendicular to the pipeline axis has been innovatively developed,and the hydrodynamic changes and sediment erosion characteristics near the pipeline after the installation of the device were studied based on the experiment.Results reveal that although the perpendicular spoiler cannot generate downforce,it can greatly increase the turbulent kinetic energy of the flow and the rate of sediment erosion.The larger the angle between the pipeline axis and the spoiler plane is,the larger the increase in turbulent energy will be.The increase in turbulent energy near the bed surface can reach up about 70%when the angle is 90°,while serious sediment erosion mainly occurs along both sides of the pipeline with a distance of about 2?4 times the pipe diameter.In the future,we can further explore the influence of the perpendicular spoiler size and installation position on the pipeline downforce and the effect of burying promotion.At the same time,field tests on the perpendicular spoiler burying aid device currently developed will conduct to observe the actual effect of perpendicular spoiler promoting pipeline scouring and burying,and improve submarine pipeline safety protection technology. 相似文献
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海底混输管线严重段塞流动的预测与控制 总被引：1，自引：0，他引：1
随着海洋油气田开发向深水海域发展,海底混输管线距离过长,且存在立管系统,容易形成严重段塞流动的现象日益严重.在严重段塞流工况下,管线的流动参数,如压降、段塞长度、段塞频率、持液率都随时间变化,并且表现为周期性变换的压力波动以及间歇出现的液塞.严重段塞流的不稳定性给油气田集输系统的设计及运行管理造成了巨大的困难.本文介绍了海底混输管线中严重段塞流动预测与控制的实验与理论研究进展,同时,对于节流、气举、分离等8类15种控制严重段塞的方法分别进行了评述,旨在为进一步开展海底油气混输管线严重段塞流动的研究提供借鉴,为工程实践提供参考. 相似文献