This paper introduces modeling and simulation results for pipeline inspecti
on gauge (PIG) with bypass flow control in natural gas pipeline. The dynami
c behaviour of the PIG depends on the different pressure across its body an
d the bypass flow through it. The system dynamics includes: dynamics of dri
ving gas flow behind the PIG, dynamics of expelled gas in front of the PIG,
dynamics of bypass flow, and dynamics of the PIG. The bypass flow across t
he PIG is treated as incompressible flow with the assumption of its Mach nu
mber smaller than 0.45. The governing nonlinear hyperbolic partial differen
tial equations for unsteady gas flows are solved by method of characteristi
cs (MOC) with the regular rectangular grid under appropriate initial and bo
undary conditions. The Runge-Kuta method is used for solving the steady flo
w equations to get initial flow values and the dynamic equation of the PIG.
The sampling time and distance are chosen under Courant-Friedrich-Lewy (CF
L) restriction. The simulation is performed with a pipeline segment in the
Korea Gas Corporation (KOGAS) low pressure system, Ueijungboo-Sangye line.
Simulation results show us that the derived mathematical model and the prop
osed computational scheme are effective for estimating the position and vel
ocity of the PIG with bypass flow under given operational conditions of pip
eline.