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Hill Instability Analysis of TLP Tether Subjected to Combined Platform Surge and Heave Motions 总被引：1，自引：0，他引：1
This paper presents the Hill instability analysis of Tension keg Platform （TLP） tether in deep sea. The 2-D nonlinear beanl model, which is undergoing coupled axial and transverse vibrations, is applied. The governing equations are reduced to nonlinear Hill equation by use of the Galerkin＇ s method and the modes superposition principle. The Hill instability charted up to large parameters is obtained. An important parameter M is defined and can be expressed as the functions of tether length, the platform surge and heave motion amplitudes. Some example studies are performed for various envirotnnental conditions. The results demonstrate that the nonlinear coupling between the axial and transverse vibrations has a significant effect on the response of structure. It needs to be considered for the accurate dynamic analysis of long TI2 tether subjected to the combined platfolna surge and heave motions. 相似文献
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整体式止屈器可有效抑制海底管道屈曲传播并避免管道的大规模屈曲失效。为探究整体式止屈器的止屈特性,预测其穿越压力,利用ABAQUS软件建立有限元模型,分析了整体式止屈器厚度、长度、径厚比等参数对穿越压力和穿越形式的影响机制,揭示了整体式止屈器的止屈特性。研究结果表明:在平行穿越阶段,增加止屈器厚度、有效长度可明显提升穿越压力;而在垂直穿越阶段,穿越压力增长速率明显放缓。结合有限元模拟结果,拟合得到了整体式止屈器在不同穿越形式下的穿越压力预测公式,其相较于已有经验公式准确性更高,对整体式止屈器的设计和建造具有重要的指导意义。 相似文献
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在一定来流条件下,张力腿平台(tension leg platform,简称TLP)的立柱后缘出现周期性的交替旋涡脱落,致使立柱受到垂直于来流方向的升力和平行于来流方向的阻力作用,导致TLP产生大幅度往复运动,显著增加平台结构和系泊系统的负载。目前,关于单柱、多柱结构绕流问题的研究较多,但对于TLP绕流特性的研究较少,机理尚存不明确的地方。为研究TLP的绕流力变化情况和流场特征,开展了数值模拟分析。利用计算流体动力学数值模拟软件,基于雷诺平均(RANS)法和分离涡模拟(DES)法对TLP绕流场进行仿真分析,揭示了TLP的绕流特性。结果表明,在3种来流角度和多个折合速度Vr下,TLP绕流的流体力系数存在明显差异,升力系数时域曲线呈现脉动性。TLP的上、下游立柱间存在明显的相互作用,影响了旋涡的形成与发展。TLP的旋涡脱落大多集中在平台固有频率附近,且在Vr=7,来流角度为0°时,升力系数频谱峰值最大,旋涡脱落集中。 相似文献
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Prediction of streamwise flow-induced vibration of a circular cylinder in the first instability range 总被引：1，自引：0，他引：1
The streamwise flow-induced vibration of a circular cylinder with symmetric vortex shedding in the first instability range is investigated, and a wake oscillator model for the dynamic response prediction is proposed. An approach is applied to calibrate the empirical parameters in the present model; the numerical and experimental results are compared to validate the proposed model. It can be found that the present prediction model is accurate and sufficiently simple to be easily applied in practice. 相似文献
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The behavior of vortex-induced vibration of a two-degree-of-freedom cylinder near a deformable wall in steady flow is investigated experimentally.The typical phenomenon of the two-degree-of-freedom cylinder’s VIV is discussed.The influences of initial gap between the cylinder and the wall on the dynamic responses of the cylinder are analyzed.The comparison is made about dynamic responses of the cylinder with one and two degrees of freedom.Experimental results show that the vibration of the cylinder near a deformable wall with a small value of initial gap-to-diameter ratios can generally be divided into two phases.The initial gap-to-diameter ratios have a noticeable influence on the occurrence of transverse vibration.The transverse maximum amplitude of the cylinder with two degrees of freedom is larger than that of the cylinder with one degree of freedom under the condition with the same values of other parameters.However,the vibration frequency of the cylinder for the two degrees of freedom case is smaller than that for the one degree of freedom case at the same value of Vr number. 相似文献
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海洋立管、海底管线和浮式平台系泊缆等柔性圆柱结构的流激振动会造成严重的疲劳损伤。目前,关于单根柔性圆柱流激振动的研究较多。为研究多根柔性圆柱系统的流激振动特性,开展了双柔性圆柱流激振动的模型试验。采用模态分析法将试验测量应变转化为位移。通过分析双柔性圆柱在并列、串列和交错排布方式下的响应位移、控制频率,揭示了双柔性圆柱的流激振动特性。研究结果表明:柔性圆柱并列排布时,两圆柱的相互作用使结构顺流向位移增大;柔性圆柱串列排布时,受遮蔽效应的影响,下游圆柱控制模态较低。由于柔性圆柱的多模态响应特性,"锁频"区后下游圆柱的位移并未显著增大;柔性圆柱交错排布时,下游圆柱发生"Wake-flutter",横流向和顺流向的控制频率接近,顺流向的位移显著增大。 相似文献
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面对通航区很可能发生的船舶抛锚、落物以及沉船等事故造成的危险,使用新型沉箱防护设施对水下生产系统进行安全防护,但目前撞击载荷下沉箱防护设施的安全评估标准并无明确界定。采用有限元方法对水下生产系统沉箱安全防护设施的撞击损伤进行了深入研究,考虑不同落物形状、下落速度、落物质量、碰撞位置对沉箱防护设施撞击损伤的影响。结果表明,锚、长方体落物对沉箱撞击最严重;撞击速度和落物质量与撞击应力成正比;对于非对称开孔的沉箱顶盖,距离开孔较近区域为应力敏感区,受到撞击时撞击应力较大。 相似文献