NUMERICAL-METHODS FOR MODELING WATER-QUALITY IN DISTRIBUTION-SYSTEMS - A COMPARISON

A comparison is made between the formulation and computational perform ance of four numerical methods for modeling the transient behavior of water quality in drinking-water-distribution systems. Two are Eulerian -based (the finite-difference and discrete-volume methods) and two are Lagrangian-based (the time-driven and event-driven methods). The Eule rian approaches move water between fixed grid points or volume segment s in pipes as time is advanced in uniform increments. The Lagrangian m ethods update conditions in variable-sized segments of water at either uniform time increments or only at times when a new segment reaches a downstream pipe junction. Each method is encoded into an existing dis tribution-system simulation model and run on several pipe networks of varying size under equal accuracy tolerances. Results show that the ac curacies of the methods are comparable. The Lagrangian methods are mor e efficient for simulating chemical transport. For modeling water age, the time-driven Lagrangian method is the most-efficient while the Eul erian methods are more memory-efficient.