Time Discretization for Fixed Grid MOC in Pipeline Systems

Abstract Transient fluid flow is the means by which changes in steady state flow and pressure are achieved. When conditions in a pipeline are changed, such as by closing a valve or starting a pump, a series of waves are generated. These local disturbances propagate with the velocity of sound within the medium until dissipated down to the level of the new steady state by the action of some form of damping or friction. In the case of flow in a pipeline, these fluid transients are the direct means of achieving all changes in fluid velocity, gradual or sudden. It is for this reason that transient flow models can perform as the backbone of a general hydraulic analysis program capable of solving problems from steady state to full transient conditions. When sudden changes occur within in a network, the benefits of a transient model are obvious, since large pressure waves of considerable magnitude can occur and are capable of destroying the pipe. However, the benefits of an integrated approach also include (i) the need to maintain only one program and set of data would have to maintained, allowing records and data bases to be more conveniently up-dated; (ii) a variety of data could be easily and accurately assimilated, thereby encouraging more accurate, complete and reliable reporting of field data; (iii) compared to several dedicated programs, a single integrated code could have considerable programming benefits, including reducing code size and memory requirements, as well as run times.