Dynamic analysis and simulation of long pig in gas pipeline

• We derived the motion equations of long pig considering the pig's length.
• In modeling the long pig, pig is considered as a chain body not a particle.
• An algorithm is proposed to solve the equations of motion of the long pig and simulate the pig's motion in gas pipeline.
• Comparison of the particle model's and long pig model's result shows that the particle model cannot be used for long pigs.

This paper deals with the dynamic analysis and simulation of long pig through the two-dimensional gas pipelines. In the modeling, the pig's length is noticed. The long pig is considered as a chain body not a particle. Pig is divided into a number of elements, Newton's second law is written for all the different elements of pig and then all the equations are added to get the dynamic equation of the pig's motion. An algorithm is used to solve the differential equation of the motion based on Runge–Kutta method. Continuity, momentum and the state equations are employed to achieve the gas flow parameters like density, velocity and pressure along the pipeline since the dynamic behavior of the pig depends on the flow field characteristics. It is assumed that pig is long and there is a bypass valve in pig's body. The path of the pig or geometry of the pipeline is considered as 2D curve. Numerical examples are chosen to show the application of the proposed formulation and algorithm. The simulation results illustrate the validity and efficiency of the derived equations for online estimating of the position and velocity of the long pig in gas pipelines at any time of the motion.