【作者】 付冰；

【导师】 戴光；

【作者基本信息】 大庆石油学院 ， 化工过程机械， 2008， 硕士

【摘要】 穿越河流管道在水流作用下,可能因冲刷而形成悬跨。管道悬跨段由于没有土壤支撑,在尾流旋涡的作用下易产生振动。若管道存在轴向裂纹型缺陷,其承压能力会下降,再加上旋涡引起的疲劳载荷,在服役中会导致其突然失效,影响正常生产、带来环境污染,给国民经济造成巨大损失。本文针对上述问题,对水流作用下悬空管道绕流场进行数值分析。并在此基础上,研究含轴向裂纹缺陷悬空管道在多种载荷联合作用下缺陷处的应力和管道疲劳寿命。主要内容如下:1、管道绕流特性及绕流理论水下管道形成悬跨后,在一定流速时,管道后面旋涡泄放频率可能接近管道的自振频率,从而出现垂直于水流的类似共振现象,并导致沿水流方向的振动和拖曳力的增大。管道两个方向的振动可产生很大的交变应力,使管道发生疲劳破坏。2、高雷诺数下静止管道绕流数值分析根据流体力学和计算流体力学理论,研究高雷诺数情况下静止管道绕流场,在计算模拟中监视管壁的升力系数和阻力系数,并得出管道绕流的涡量等值线分布、压力分布、切应力分布。3、均匀流中悬空管道横向振动数值分析研究悬空管道的横向振动,横向涡激振动对疲劳失效的影响远大于顺流向涡激振动的影响,因此,为避免发生横向涡激振动,计算不同频率比条件下的升力系数、阻力系数、升力系数功率谱及涡量等值线分布图,确定管道发生“锁频现象”的频率比,得出水下输油管道悬空段的临界长度。4、水流作用下含轴向裂纹缺陷管道数值分析建立悬空管道的计算模型,结合管道的支撑条件,研究含缺陷管道在多种载荷联合作用下的缺陷应力分析和疲劳寿命分析。更多还原

【Abstract】 In water, pipeline is possibility washed out to be suspended span. Because pipeline’s suspended span does not have the soil support, it is easy to vibrate under the vortex’s function. When existed axial crack flaw in pipe, coupled with fatigue failure caused by the vortex, its bearing pressure ability will drop. In the service the pipeline will lead to a sudden failure. It will affect the normal production , bring the environmental pollution and causing huge losses to the national economy.In this paper, numerical simulation of water flow around a suspended pipe is done. The suspended pipe with axial crack flaw has many kinds of load joint action. Using the results, pipe’s defects stress analysis, internal pressure analysis and fatigue life are studied. This paper main research content includes:1、Flow characteristic and theory around pipeIn a certain velocity, relief frequency eddy behind the suspended pipe could be close to the natural frequency channels. Thus similar resonance effect vertical to the flow appears. It leads the vibration along the flow direction and drag increase. Two directions of vibration could be produce great alternating stress, which causes the pipeline to have the fatigue failure.2、Numerical analysis of water flow around pipe under high reynold numberAccording to hydromechanics and computation hydromechanics theory, numerical analysis of flow around a pipe under high reynold number is studied. Lift and drag coefficients are monitored, and eddy contours of the distribution, pressure distribution, shear stress distribution are analyzed.3、Numerical analysis of viscous flow around a suspended pipe resonant transversely in a uniform streamThe fatigue failure of transverse vortex-induced vibration is far greater than the downstream. Therefore, in order to avoid the transverse vortex-induced vibration, lift coefficient, drag coefficient, vortex contours of the distribution and power spectrum of lift coefficient under the different frequency ratios are calculated. When“frequency-locking phenomenon”occurrences, control of suspended pipe’s vacant length is calculated.4、Numerical simulation of pipe with axial crack flaw underwaterComputation model of suspended pipe is established. The suspended pipe with axial crack flaw has many kinds of joint loads and different support conditions. Pipe’s defects stress analysis and fatigue life is analyzed.更多还原