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1.
平台运动下悬垂立管动力响应及疲劳损伤特性试验研究 总被引：1，自引：0，他引：1
悬垂立管因其经济性被广泛应用在深海油气开发中。悬垂立管在顶端平台运动作用下,会不断产生横流向以及顺流向动力响应,循环累积造成疲劳损伤。为了研究悬垂立管在平台运动作用下的疲劳损伤特性,开展了大尺度悬垂立管模型试验。采用小波分析、模态分析、雨流计数法等方法处理分析试验数据。分析平台运动下无内流作用下大尺度悬垂立管动力响应及疲劳损伤特性,发现横流向弯曲应变结果较为复杂,局部呈现行波特性,主导频率具有时变性。相比之下,顺流向弯曲应变结果比较有规律性,整体呈现行波特性,主导频率不具有时变性,并始终保持与顶端平台运动频率相同。平台运动引发的悬垂立管涡激振动疲劳损伤和KC数有关。各点面内疲劳损伤值延管长分布趋势和面内应变RMS延管长分布趋势相似。横流向(CF方向)的疲劳损伤的数量级为顺流向(IL方向)的10-2倍左右。 相似文献
2.
不考虑波浪、海流以及平台运动的作用,研究管内流动对冷水管动力性能的影响。基于悬臂输液管道梁模型,通过轴向流速比α、流速角比ψ和切向流速比φ三个进流口流场参数描述自由端边界条件,获得冷水管在内流作用下的控制方程。从流体动力项对管道做功的角度分析发现,φ对管道失稳的临界流速有很大的影响,并且φ=0被认为是对进流口流场的正确描述;然而,通过Galerkin法分析发现,φ=0的进流口流场模型不能解释进流口压降Δp对动态失稳基本没有影响的试验现象。相反,φ≠0的进流口流场模型在使得进流口压降Δp的影响几乎为零的同时,还能够获得较大的临界流速,与Kuiper观察的试验现象相符。切向流速比φ的正确评估是准确预测临界流速的前提条件。 相似文献
3.
海底管道管跨段在内外流体作用下的竖向动力特性研究 总被引：2，自引：0，他引：2
根据在复杂的海洋环境条件下,管道的动力特性受到内外流体的综合作用影响,呈现与陆地管道不同的特点。研究了结构受到外界流体所产生的涡激作用,同时考虑管内恒定流的影响,利用有限元方法对海底管道管跨段竖向振动的微分方程进行求解。在此基础上得出了管跨段在不同外流流速情况下,内流流速与结构动力响应幅值的关系及其对管跨段振动频率的影响,并进一步探讨了管跨失稳时的极限管内流速与跨长的关系,这些结论对于海底管道设计具有一定实际指导意义。 相似文献
4.
通过大长细比海洋立管物理模型试验,研究内流对其顶张力的影响。在不同的外流流速下用电子流量计读出内流流速,用动态电阻应变片测试得到顶端张力;然后直接分析内流对顶张力的影响规律。试验研究表明:内流的增加会使顶张力减小;施加的初始顶张力较大时,内流的影响较小;施加的外流较小时,内流对顶张力的影响较大。 相似文献
5.
在深海采矿车布放回收中,准确预报脐带缆在底部自由悬垂边界条件和顶部波浪载荷随机激励等共同影响下的动力响应是关键点之一。基于三维势流理论与集中质量法,结合水面支持船运动和海流联合激励,对深海布放回收中脐带缆的顶端张力等力学特性进行研究。结果表明：在布放回收过程中,轴向张力在结构载荷中占主要成分;由波浪引起的轴向张力极值与均值差距最大可达到54%;轴向张力的频谱存在双谱峰,分别为 0.14 Hz的主峰和0.10 Hz 的次峰;当浪向角为180°时,轴向张力处于峰谷。 相似文献
6.
海洋立管复模态动力特性分析 总被引：1，自引：0，他引：1
考虑阻尼的影响,研究海洋立管的动力特性。通过分析管内流体及管外海洋环境荷载的共同作用,建立海洋立管涡激振动偏微分方程,进而得到立管动力特性方程,用复模态分析法求解动力特性方程得到立管考虑阻尼的自振频率。算例计算表明:考虑阻尼的立管自振频率略小于不考虑阻尼的立管自振频率;立管的自振频率随着内流流速的增加而减小,但内流流速不大时,影响较小;管道长度对立管的自振频率影响较大。 相似文献
7.
深海采矿系统中的软管段是连接中继仓和集矿车必不可少的环节。因受力学特性、海底地形及回采工艺等多种约束条件的作用,其空间形态复杂,对输送工艺和参数匹配要求比较苛刻。基于深海采矿软管输送模拟试验系统,分析了不同工况条件下软管形态动态变化特征及其规律,其结果表明:软管空间形态影响因素主要有集矿车移动距离、内流流速和内流密度,其中,当拱顶高度不受水面高度限制时,集矿车自由移动距离增大和内流流速增加均使软管角度呈线性增长趋势;而当内流为浆体时,软管形态变化趋势与清水内流一致,但软管隆起幅度较小,主要是因为浆体密度远大于清水密度,单位流体重力增幅大于流体向上冲力的增幅,且两侧下垂更加明显。通过研究软管形态变化规律及内在机理,为深海采矿系统输送参数优化及匹配提供研究基础。 相似文献
8.
海洋输流立管耦合动力分析 总被引：1，自引：1，他引：0
综合考虑黏性内流以及立管轴向和流向的耦合效应等多种因素对立管动力响应的影响,基于Hamilton原理推导得出海洋立管耦合振动方程,采用Galerkin法进行数值求解。首先分析波流载荷与平台运动联合激励和仅在平台运动作用下立管动力响应的差异,然后讨论黏性内流和顶部张力对立管动力特性和响应峰值的影响。计算结果表明:波流与平台运动耦合作用和仅在平台运动作用下的立管各阶振动模态和振动峰值存在明显差异,波浪和海流对立管的直接作用不可忽略;内流运动黏性会改变立管振型峰值,立管流向一阶固有频率随内流流速增大而减小,流向和垂向振动峰值分别随之增加和减小,但这种影响很有限,且可以通过增大立管顶部预张力来抵消。 相似文献
9.
海底输液管道内流、轴向力和压强对允许悬空长度的影响 总被引：1，自引：0，他引：1
以海底悬跨段输液管道为研究对象,考虑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。由于内流流速项的影响,使得导出的管道振动微分方程不能用振型分解法直接求解,故本文将解表示为具有正弦和余弦的对称和反对称的各个空间振型的总和,从而求出悬跨段管道固有频率。为防止管道发生横向涡激振动,用约化速度作为控制条件,求解出管道允许悬空长度。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,随着轴向拉力的加大而增大。 相似文献
10.
多跨输液管的稳定性及动力响应 总被引：2，自引：0，他引：2
本文研究了在工程中常见的支承在多个弹性支座上的输液管系，用Ｈａｍｉｌｔｏｎ原理和有限元法建立管道系统的运动方程，通过求解带有陀螺矩阵的振动方程组的特征值问题计算了这种管系的临界流速，结果表明，前两阶模态的临界流速相同，且明显高于单跨管的最低临界流速；用威尔逊－θ逐步积分法考察了管系在临界流速附近对扰动的响应，结果表明，当小于临界流速时，响应主要是低频周期振动；反之，则位移随时间按指数增长 相似文献
11.
Numerical study about vortex-induced vibration(VIV) related to a flexible riser model in consideration of internal flow progressing inside has been performed.The main objective of this work is to investigate the coupled fluid-structure interaction(FSI) taking place between tensioned riser model,external shear current and upward-progressing internal flow(from ocean bottom to surface).A CAE technology behind the current research which combines structural software with the CFD technology has been proposed.According to the result from dynamic analysis,it has been found that the existence of upward-progressing internal flow does play an important role in determining the vibration mode(/dominant frequency),vibration intensity and the magnitude of instantaneous vibration amplitude,when the velocity ratio of internal flow against external current is relatively high.As a rule,the larger the velocity of internal flow is,the more it contributes to the dynamic vibration response of the flexible riser model.In addition,multi-modal vibration phenomenon has been widely observed,for asymmetric curvature along the riser span emerges in the case of external shear current being imposed. 相似文献
12.
《中国海洋工程》2020,(3)
An experimental investigation on the disturbance effect of jet-type active vibration suppression device on vortexinduced vibration of deep-sea riser was carried out in the wave-flow combined flume. The vibration suppression device was designed in which the jet pipe was horizontally fixed to the front end of the riser. By varying three different excitation spacings and multi-stage outflow velocities, the influence law of the dominant frequency,dimensionless displacement and other dynamic response parameters was studied under different excitation spacings,and the mechanism and sensitive characteristics of the disturbance suppression were explored. The results indicate that the variation of excitation spacing makes gas curtain enter the strong disturbed flow region at different velocities and angles, and the coupling relationship between excitation spacing and reduced velocity is the key factor to enter the strong disturbed flow region to achieve the optimal disturbance suppression. In the strong disturbed flow region,the influence of gas curtain on the dominant frequency is obviously affected by the flow velocity, while the vibration displacement is stable at the same amplitude and is weakly affected by the flow velocity. Gas curtain can effectively disturb the formation of vortex shedding, destroy the strong nonlinear coupled vibration of the riser, and achieve better vibration suppression effect. In the weak disturbed flow region, the vortex length of the riser tail is prolonged,the strong nonlinear coupled vibration of the riser is gradually restored, and the vibration suppression effect of the device gradually decreases. 相似文献
13.
The vibration response of a free-hanging flexible riser induced by internal gas-liquid slug flow was studied experimentally in a small-diameter tube model based on Froude number criterion. The flow regime in a curved riser model and the response displacements of the riser were simultaneously recorded by high speed cameras. The gas superficial velocity ranges from 0.1 m/s to 0.6 m/s while the liquid superficial velocity from 0.06 m/s to 0.3 m/s. Severe slugging type 3, unstable oscillation flow and relatively stable slug flow were observed in the considered flow rates. Severe slugging type 3 characterized by premature gas penetration occurs at relatively low flow rates. Both the cycle time and slug length become shorter as the gas flow rate increases. The pressure at the riser base undergoes a longer period and larger amplitude of fluctuation as compared with the other two flow regimes. Additionally, severe slugging leads to the most vigorous in-plane vibration. However, the responses in the vertical and horizontal directions are not synchronized. The vertical vibration is dominated by the second mode while the horizontal vibration is dominated by the first mode. Similar to the vortex-induced vibration, three branches are identified as initial branch, build-up branch and descending branch for the response versus the mixture velocity of gas-liquid flow. 相似文献
14.
Dynamic Characteristics of Marine Risers Conveying Fluid 总被引：10，自引：0，他引：10
The lateral vibration differential equation for a marine riser conveying fluid is derived by useof the small deflection theory.and the effect of internal flow velocity and top tension on the natural fre-quency of the riser is studied by use of FEM.At the same time,the preliminary relationship between thenatural frequency and riser span under different internal flow velocities is obtained,the effect of riser sup-ports on the vibration frequency is computed.It is found that the natural frequency of the marine riser in-creases with the increase of top tension.however decreases with the increase of internal flow velocity.In ad-dition,the frequency decreases drastically with the increase of riser span. 相似文献
15.
海洋环境荷载下输液立管的静、动力特性研究 总被引：1，自引：1，他引：1
考虑管内流动流体和管外海洋环境荷载共同作用 ,建立海洋立管侧向运动微分方程。用Hermite插值函数离散 ,在微机上编写海洋立管静、动力分析程序 ,通过计算分析研究管内流体对立管侧向变形和应力的作用 ;另外 ,探讨管内流体的流动速度和立管顶端的预张力对立管动力特性的影响。结果表明 ,立管变形和应力均随管内流体流动速度增加而增大 ,同时内流速度的增大会降低立管的固有频率 ,但适当增大立管顶端预张力会抵消内流流速增加引起的固有频率下降。 相似文献
16.
The vortex-induced vibration test of the deep-sea riser was carried out with different excitation water depths in the wave-current combined water flume.By dimensionally changing the multi-stage water depth and hydrodynamic parameters such as outflow velocity at various water depths,the dynamic response parameters such as dominant frequency,dimensionless displacement and vibration trajectory evolution process of the riser under different excitation water depths were explored to reveal the sensitive characteristics of the dynamic response of vortexinduced vibration of the risers under different excitation water depths.The results show that different excitation water depths will change the additional mass of the riser and the fluid damping and other parameters,which will affect the spatial correlation and stability of the vortex shedding behind the riser.In the lock-in region,the distribution range of the characteristic frequency becomes narrow and centered on the lock-in frequency.The increase of the excitation water depth gradually advances the starting point of the lock-in region of the riser,and at the same time promotes the excitation of the higher-order vibration frequency of the riser structure.Within the dimensionless excitation water depth,the dominant frequency and dimensionless displacement are highly insensitive to the excitation water depth at high flow velocity.The change of the excitation water depth will interfere with the correlation of the non-linear coupling of the riser.The“8-shaped”gradually becomes irregular,and the vibration trajectories of the riser show“O-shape”,“X-shape”and“Crescent-shape”. 相似文献
17.
管内流动会影响输流管的振动响应,目前关于输流弹性管涡激振动方面的研究较少。基于计算流体力学(CFD)方法,开展内外流对细长输流弹性管振动特性影响的研究。首先在不考虑内流的情况下将弹性管涡激振动数值预报结果与模型试验数据进行对比,验证了数值方法的可靠性。再者考虑内外流耦合作用情况下,对不同内流流速下细长输流弹性管振动位移时—空分布、顺流向最大平均偏移、振动轨迹、内部横向涡的形成与分布等进行了对比分析。结果发现,与外流流速相比,内流流速的增加虽然难以改变弹性管的主振模态,但对沿管体的振动强度影响显著。顺流向最大偏移处管体运动轨迹发生明显的变形和跳跃。在剪切外流和均匀内流对弹性管的联合作用下,沿管跨方向模态间能量转换频繁,伴随着间歇性出现或消失的沿弹性管传播的行波组分,这主要归因于复杂的双重流固耦合系统(外流—管体,内流—管体)。在内流以附加质量力、离心力和科氏力形式的激励下,弹性管内二次流现象明显。在振动过程中,内部横向涡沿管壁生成、脱落并逐渐散布于整个横截面。 相似文献
18.
This study deals with the nonlinear dynamic response of deep-sea risers subjected to parametric excitation at the top of a platform.As offshore oil and gas exploration is pushed into deep waters,difficulties encountered in deep-sea riser design may be attributed to the existence of parametric instability regarding platform heave motions.Parametric resonance in risers can cause serious damage which might bring disastrous accidents such as environment pollution,property losses and even fatalities.Therefore,th... 相似文献
19.
Cold-water pipe (CWP) is a novel, most-challenging component of Ocean Thermal Energy Conversion (OTEC) floating structure which is installed to transport the deep seawater to the board. For commercial scale, the transported seawater flow rate will be in the order of 102 m3/s. This large amount of internal flow may trigger instability which leads to the failure of CWP. Considering this issue, the present paper aims to design commercial-scale OTEC CWP focusing on the effects of internal flow to the stability of the pipe. The design analysis is deliberated to select the pipe material, top joint configuration (fixed, flexible, pinned) and bottom supporting system (with and without clump weight). Initially, the analytical solution is built by taking into account the components of the pipe dynamics. Separately, a fully coupled fluid-structure interaction analysis between the pipe and the ambient fluid is carried out using ANSYS interface. Using scale models, the results obtained from the analytical solution are compared with the ones from numerical analysis to examine the feasibility of the analytical solution. After being verified, the analytical solution is used to observe the dynamic behavior of the CWP for 100 MW-net OTEC power plant in the full-scale model. The results yield conclusions that pinned connection at the top joint is preferable to decrease the applied stress, clump weight installation is necessary to reduce the motion displacement and Fiber Reinforced Plastic (FRP) is the most suitable material among the examined materials. 相似文献