Transient Pig Motion Through Non-Isothermal Gas and Liquid Pipelines

Simulation of the dynamics of pigs moving through non-isothermal pipelines is presented. The differential mass, linear momentum and energy equations were numerically solved by a finite difference numerical scheme, for compressible flow through pipelines. The fluid flow equations were combined with an equation representing a force balance on the pig. Pressure forces developed due to flow through by-pass holes in the pig, pig acceleration and pig/pipe contact forces were considered. A stick/slip model was developed to account for the distinct friction regimes that prevail depending on whether the pig is stopped or in motion. An adaptive grid technique was employed to account for the moving pig. Heat losses to the ambient play an important role in the fluid temperature distribution. However, for the test cases conducted, the temperature variations caused virtually no effect on the pig dynamics.