共查询到19条相似文献,搜索用时 187 毫秒
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利用水动力经验模型,用简易的图解法预报不同功能载荷和边界条件下的深水悬跨管道涡激振动响应频率和振幅.分析内流流速、阻尼和管土耦合作用等因素对涡激振动响应及锁定范围的影响.指出对于低流速内流,特别是有效张力比较大的时候,内流流速对结构固有频率影响很小;管土耦合边界对悬跨振动响应的主要作用在于减小结构固有频率和提高阻尼,有利于减少疲劳累积损伤预报值. 相似文献
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为有效预测腐蚀条件下海底悬跨管道的涡激振动响应,基于Euler-Bernoulli梁理论和改进范德波尔尾流振子方程,引入裂纹梁的等效抗弯刚度,建立考虑腐蚀作用的海底悬跨管道涡激振动模型。运用该模型对海底悬跨管道进行振动分析,并将计算所得结果与通过有限元建立的腐蚀管道模型所得结果相对比,验证该模型的准确性。通过分析不同腐蚀深度下海底悬跨管道的涡激振动特性发现:考虑腐蚀作用的管道在固有频率、位移响应和应力响应等方面与完整管道差异较大,且随着腐蚀深度的增加,变化率逐渐增大;考虑腐蚀作用的管道在发生涡激振动时的不稳定性比未考虑腐蚀作用的悬跨管道更强。 相似文献
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波流共同作用下隔水管动力响应非线性分析 总被引:2,自引:1,他引:2
为了探讨在波浪海流共同作用下隔水管的动力响应及涡激振动力分析,根据三维空间中隔水管运动的微分控制方程,以:MatteoIuca改进的Vanderpol尾流振子模型为基础计算涡激振动时隔水管与流体之间的相互作用.通过Hermite插值函数对隔水管的运动微分方程进行有限元离散,基于非线性分析理论利用当前拉氏描述(UL)建立了考虑几何非线性、预应力、涡激流固耦合等复杂因素影响的综合非线性增量平衡方程,并采用New-ton-Raphson迭代法和Newmark方法相结合的方法建立了空间隔水管非线性涡激动力响应的增量迭代算法.最后给出了考虑几何非线性与对外界荷载作用简化的位移分布包络线.以及横向涡激振动响应曲线.计算结果表明,所采用的方法正确、有效,可以为隔水管的生产没计及理论分析提供依据. 相似文献
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多跨管道由于其自振频率低且相邻模态频率临近,容易在低流速下产生多模态涡激振动.针对长期作业的海底多跨管道,考虑遭遇海流流速变化以及涡激振动响应本身的随机性,多模态响应采用单频响应的等效组合,利用 N-S曲线和Miner线性累积损伤准则进行悬跨涡激振动疲劳损伤简化预报,为深水悬跨管道初始设计提供参考.通过一输气多跨管道的疲劳累积损伤度的影响因素分析,结果表明:疲劳损伤对土壤刚度选取敏感;DNV RP-105规范中多模态响应缩减系数较振幅权重形式更保守;用Rayleigh分布描述涡激振动响应进程计算的疲劳损伤要高于恒幅稳态振动描述. 相似文献
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悬链线立管会在半潜平台运动带动下出现涡激振动现象,对立管疲劳寿命造成影响.借助海工结构物动力分析软件Orcaflex建立立管模型,使用Iwan-Blevins尾流振子模型进行数值模拟.通过与试验结果对比验证了该方法的可行性.同时建立实尺度悬链线立管模型,并考虑背景海流的影响,分析平台垂荡、纵荡运动下的立管涡激振动响应和疲劳损伤.研究表明,平台运动产生的非定常流场将引起悬链线立管发生涡激振动现象,并在背景洋流激励的基础上增大疲劳损伤,在立管结构实际工程设计时应予以关注. 相似文献
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由于高阶响应对结构涡激振动存在显著影响,文中在考虑其影响的前提下利用经典Van der Pol尾流振子模型研究了立管在均匀流中的涡激振动特性。在尾流振子与结构模型的相互作用中同时考虑了一阶响应和高阶响应的影响,从而推导了一种考虑了一阶—高阶响应的涡激振动模型。并在此基础上,分析了考虑位移、速度和加速度三种不同右端耦合项作用下的响应特性。此外,还针对不同的质量阻尼比,比较了考虑高阶响应影响和未考虑高阶响应影响情况下系统的涡激振动特性。结果表明,考虑一阶—高阶响应的理论模型能更精确地反映该系统的振动特性。尾流振子和立管的运动幅值都有一定程度的增大。尽管计算结果显示高阶响应比一阶响应小若干个量级,但是不可以忽视高阶响应,因为它对一阶响应存在明显的影响。 相似文献
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本文应用改进的尾流振子模型对振荡流下悬链线式立管的涡激振动特性进行了研究。首先基于向量式有限元建立了悬链线式立管振动控制方程,利用独立性原理和改进的尾流振子模型模拟时变的涡激升力,然后采用中央差分法求解立管的涡激振动响应。利用相应的试验结果验证了本文模型的有效性。最后,对振荡流下悬链线式立管涡激振动响应特性进行了分析。研究结果表明:振荡流下悬链线式立管响应幅值出现“振幅调制”现象,大KC(Keulegan-Carpenter)数下,进一步出现典型的“间歇涡激振动”现象;KC数对质点振动相图形状以及流固能量传递有显著影响;振荡流下立管响应峰值随流速呈“多峰”现象,KC=20时多峰现象更为明显;在小KC数范围内,较小的KC数会激励立管产生较大的涡激振动位移。 相似文献
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在海底悬跨管道安装和操作过程中会产生的高轴向力和高压力,功能载荷对管道涡激振动的影响小可忽略.本文首先基于Hamilton原理,推导并求解了简单支撑的输液张力管道自由运动方程,在此基础上利用DNv.RPl05规范评估悬跨涡激振动响应,对悬跨管道受不同功能载荷(特别是有效轴向力和内流流速)进行计算.结果显示功能载荷通过改变管道的固有频率来影响涡激振动响应,而且由于实际内流流速一般不高,其影响较有效轴向力要弱.结果可以为悬跨管道的许用长度选取提供参考. 相似文献
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The flexible cantilever riser, as a special form of the marine riser, can be encountered in a deep-sea mining system, where the bottom of the long vertical lifting pipeline is connected with the intermediate warehouse. The main objective of this paper is to investigate the effects of the bottom weight caused by the intermediate warehouse and the flow speed on the dynamic responses of the cantilever pipeline. A quasi-3D coupling algorithm based on the discrete vortex method and finite element method is employed to calculate the unsteady hydrodynamic forces and vortex-induced vibrations of this pipeline in the time domain, respectively. We first simulate the VIV of a long flexible riser with two fixed ends in a stepped flow to validate the feasibility of the present method. Then, systematic simulations of cross-flow VIV of the cantilever riser are carried out under a wide range of bottom weights and different current speeds. The number of the vibration mode shows the decreasing tendency with the increase of the bottom weight. In a certain range of the weight, the number of the dominant mode remains unchanged, while the vibration amplitude declines with increasing weight. An amplitude jump phenomenon can be observed when the transition of the dominant mode in two contiguous mode clusters occurs. Moreover, the higher-order modes are excited with the increase of the current speed. 相似文献
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讨论了目前用于海底悬跨管线涡激振动预报的主要数值模型,针对海底管线悬跨段涡激振动问题编制了有限元分析程序,程序采用梁单元模拟管跨结构,动力响应计算方法采用VIVANA模型,模型控制方程采用Newton-Raphson迭代算法求解。采用Larsen,Koushan等人(2002)和Larsen,Baarholm等人(2004)给出的两组不同的用于确定升力曲线的参数曲线进行计算,将计算结果与Tsahalis(1984,1987)的模型实验结果进行了比较。结果表明本文的涡激振动模型能够预报间隙比e/D=∞时海底悬跨管线的涡激振动响应;采用Larsen,Koushan等人(2002)参数曲线得到的计算结果与间隙比e/D=∞时的实验结果符合较好,Larsen,Koushan等人(2002)参数曲线较Larsen,Baarholm等人(2004)参数曲线更适合于海底悬跨管线的涡激振动预报。 相似文献
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复杂悬跨条件下的管线涡激振动分析(英文) 总被引:1,自引:0,他引:1
Spans occur when a pipeline is laid on a rough undulating seabed or when upheaval buckling occurs due to constrained thermal expansion. This not only results in static and dynamic loads on the flowline at span sections, but also generates vortex induced vibration (VIV), which can lead to fatigue issues. The phenomenon, if not predicted and controlled properly, will negatively affect pipeline integrity, leading to expensive remediation and intervention work. Span analysis can be complicated by: long span lengths, a large number of spans caused by a rough seabed, and multi-span interactions. In addition, the complexity can be more onerous and challenging when soil uncertainty, concrete degradation and unknown residual lay tension are considered in the analysis. This paper describes the latest developments and a .state-of-the-art. finite element analysis program that has been developed to simulate the span response of a flowline under complex boundary and loading conditions. Both VIV and direct wave loading are captured in the analysis and the results are sequentially used for the ultimate limit state (ULS) check and fatigue life calculation. 相似文献
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基于ANSYS的高精度管路系统抗冲击仿真方法及试验验证 总被引:1,自引:0,他引:1
针对船舶管路系统抗冲击性能仿真方法精度不足的问题,研究用于舰船管路系统的高精度抗冲击仿真方法。采用ANSYS有限元实体建模技术、冲击时域分析法对空间管路系统抗冲击性能进行研究,搭建管路系统抗冲击试验平台,对不同冲击载荷下管路系统的抗冲击性能进行试验验证,最后以舰艇典型管路系统为算例,研究三向冲击载荷作用下舰船管路的抗冲击性能。研究给出了基于接触单元、弹性约束、实体附件单元等高精确的管路建模技术,提出了船舶管路抗冲击时域仿真流程。研究表明,采用时域分析法和实体建模技术满足抗冲击仿真高精度的要求,舰船空间管路系统的横向抗冲击性能较差,法兰、直角弯管处、连接支管处等部位为管路系统薄弱结构。根据仿真结果,文章还提出了一系列用于工程实践的管路优化布置方法。 相似文献
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Vortex-induced vibration (VIV) of flexible risers with both internal and external flows has received much attention recently. Hence, VIV dynamics of a fluid-conveying flexible riser subjected to external shear current is investigated. The effect of internal flow velocity and fluid density on VIV response is mainly examined and analyzed. A time domain model is introduced and elaborated. Then the finite element method is adopted to discretize the governing equations. Firstly, the model is validated based on the comparison between the numerical and experimental results. Then the influence of the internal flow velocity and fluid density on VIV dynamics is studied. The results show that multi-frequency response occurs when the flexible riser with various internal flow velocities and densities is subjected to external shear current. Under same shear current velocity, the IL mean deflection is enlarged with the increase of the internal flow velocity and fluid density. In addition, the internal flow velocity and fluid density have an evident effect on the vibrating frequency and the root mean square (RMS) displacement in both in-line (IL) and cross-flow (CF) directions. Moreover, mode and frequency transitions can be observed under different internal flow velocities and fluid densities. 相似文献
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Existing VIV prediction approaches for steel catenary riser (SCR) typically employ truncation model without considering the interaction between the SCR and soil, and only allow for cross-flow (CF) VIV. In this study, a time domain approach accounting for the SCR-soil interaction is proposed to predict the CF and in-line (IL) VIV induced fatigue damage of a SCR at touchdown zone (TDZ). The hydrodynamic force resulting from the vortex shedding is modeled using the forced oscillation test data of a rigid cylinder and an empirical damping model, which are defined as functions of the non-dimensional dominant frequency and amplitude of the SCR response. Due to the coupling effect, the IL VIV force is magnified based on the CF VIV amplitude. By combining a linear hysteretic interaction model with a trench shape model, some particular phenomena during the vertical SCR-soil interaction are captured and qualitatively discussed, while for the horizontal direction, the seabed is simplified as nonlinear spring model. Based on these models, parametric studies are conducted to broaden the understanding of the sensitivity of VIV induced fatigue damage to the seabed characteristic. The results indicate trench depth, vertical and lateral stiffness, and clay suction are significantly affect the VIV induced maximum fatigue damage at TDZ. 相似文献
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