Numerical Analysis Of Fluid-structure Interaction Under Multiple Working Conditions For Differential Pressure Pipeline Robot

Differential pressure pipeline robot is widely used in the internal detection of the long-distance pipeline,but in the face of some complex structures such as elbow or tee position,there is a detection blind area,which can not grasp the influence of the flow field in the pipeline and the pipeline itself.To determine the working flow field and the change of pipeline stress when the pipeline inspection robot works in different forms of pipelines,the CFD(Computational Fluid Dynamics)method is used to simulate the working flow field of the pipeline robot,and the fluid-structure coupling analysis of the pipeline is carried out.Firstly,aiming at the flow field environment of the pipeline robot,the Navier-Stokes equations(hereinafter referred to as N-S equations)are discretized,and the discrete format and solving algorithm are determined.SIMPLE(semi-implicit Method for Pressure Linked Equations)algorithm based on fully Implicit time integral is derived.Then,the transient flow field in the working area of the pipeline robot is analyzed by using the moving grid technology,and the flow field changes of the pipeline robot in straight pipe,T-tee,and 90° bend are obtained.At the same time,the fluid-structure interaction analysis of three types of pipelines is carried out to determine the influence of the robot working in the pipeline on the pipeline stress change.Since the speed of the pipeline robot is not constant at work,the velocity of the pipeline robot is changed several times to explore the pressure and velocity changes of the flow field in the pipeline when the pipeline robot runs at different speeds.The results show that the velocity and dynamic pressure change little while the static pressure increases obviously when the pipeline robot works in the pipe.In the straight pipe,the dynamic pressure and velocity peak increase by 5% and 3%respectively,and the static pressure increases by nearly 50%,and the pipe stress increases by nearly 50%.In the t-tee,the increase of static pressure decreases gradually as the robot moves to different positions,and its peak increase rate is about 92%.The pipeline stress also decreases gradually with the decrease of static pressure,and its peak increase rate reaches 73%.The increase rate of velocity and dynamic pressure is less than 1%,which can be regarded as a calculation error.In the right Angle bending pipe,the variation range of velocity and dynamic pressure in the pipe is not more than 1%,but the static pressure in the pipe increases by 80%,and the stress in the pipe increases by more than 70%.When the robot velocity is changed in different pipes,it is found that the influence of the robot velocity on the flow field parameters tends to be the same in the three pipes,and the static pressure and dynamic pressure in the flow field decrease with the increase of the velocity.