Water hammer simulation method in pressurized pipeline with a moving isolation device

Smart isolation devices (SIDs) are commonly used in pressurized subsea pipelines that need to be maintained or repaired. The sudden stoppage of the SID may cause large water hammer pressures, which may threaten both the pipeline and the SID. This paper proposes a simulation method by using a coupled dynamic mesh technique to simulate water hammer pressures in the pipeline. Unlike other water hammer simulations, this method is the first to be used in the simulation in pipelines with a moving object. The implicit method is applied to model the moving SID since it has the mutual independence between the space step and the time step. The movement of the SID is achieved by updating the size of the computational meshes close to the SID at each time step. To improve the efficiency of the simulation and the ability of handling complex boundary conditions, the pipe sections far away from the SID can also be simulated by using the explicit Method of Characteristics (MOC). Verifications were conducted using the simulated results from the Computational Fluid Dynamics (CFD) numerical simulation. Two scenarios have been studied and the comparisons between the simulated results by using the dynamic meshes in 1D methods and those by the CFD simulation show a high correlation, thus validating the new method proposed in this paper.