Modelling of the Pipeline as a Lumped Parameter System

Abstract

The paper deals with the simplification of pipeline models. A nonlinear distributed parameters model is line- arised and its transfer function given. The pipeline is represented as a two-port system. Two causal representations - the hybrid ones which are used in practice - are studied further. They involve three different transcendent trans- fer functions which are then approximated by rational transfer functions using a Taylor series expansion. The de- rived models are valid for low frequencies and are used to discuss how to obtain better approximation. They equalise the high frequency gain of the transcendent and rational transfer functions and employ a Pade approxi- mation. Due to the approximation of the high frequency gain, the derived models are only valid for a class of models - namely - well damped pipelines. The derived models which describe the pipeline as a lumped parame- ter system were verified on a real pipeline using experiment data.