中文摘要：

油管柱失效的主要形式是油管螺纹连接失效。目前对油管螺纹连接失效的研究主要集中在载荷作用下的螺纹受力和变形分析,对螺纹连接处流场突变导致失效的研究较少。利用流体动力学计算方法,对API圆螺纹油管接箍流场内部的流体建立控制方程,采用FLUENT软件进行流场模拟,对接箍连接的＂J＂形区的压力、速度分布情况进行了分析,并提出了改进措施,对流道进行优化。＂J＂形区的流场模拟计算发现,流体因高速流动产生涡流和压力突变,进一步影响流体性质并冲击接箍内壁。API油管接箍结构优化后,避免了压力和速度的突变,有利于流体流通,为油管的优化设计提供了理论依据。

英文摘要：

The thread connections invalid of API tubing is the main form of tubing string failure according to the statistics from oilfields.Study on thread connection failure has been mainly focused on the force and deformation analysis under loads,few have been related to the flow field mutations of threaded connections.Therefore,it is necessary to study the failure mechanism by flow field mutations.In this paper,based on the computation fluid dynamics,governing equations of flowing fluid in thread connection have been built.Then,flow characteristics（distribution of pressure and velocity）in the connection of API round thread tube were simulated by FLUENT.Finally,technical measures that can improve the flow mutations have been proposed.According to the simulation and calculation of flow field in the ＂J＂-shaped area,it was concluded that vortex and pressure mutation induced by high-speed flow would affect the fluid properties,leading the fluid to attack the inner wall of the connection.The newly designed API round thread could avoid the mutation of pressure and velocity,which was favorable for fluid flow,providing theoretical basis for the optimization design of tube.