A numerical model for simulating flows in either sewer or open channel systems is presented. The physical phenomenon of one-dimensional unsteady flow described by the St. Venant flow equations is examined for a more accurate and stable solution under a wide variety of physical conditions experienced in sewer or channel systems. A sparse matrix technique associated with a staggered grid numerical system is developed to solve the flow equations implicitly. Use of this sparse matrix technique leads to a substantial reduction in the order of the sparse matrix and the requirement of computer memory. The model is established without any omission of the terms in the St. Venant equations under the flow and depth conditions experienced in the sewer or open channel systems. The application of the model to a large complex looped sewer system shows that the model achieves a significant improvement in computational speed compared with the USEPA EXTRAN model and can still maintain similar accuracy. The model is especially suitable for real time control purposes since the simulation time of the model is almost negligible in comparison to the real time physical process even for a large looped system. The simulation also shows that base flow is practically not required far the model when the system is dry. Copyright (C) 1996 IAWQ. Published by Elsevier Science Ltd.
