Accounting for uniformly distributed pipe demand in WDN analysis: enhanced GGA

The global gradient algorithm (GGA) is the most widely adopted method for steady-state analysis of water distribution networks. It is used to solve the non-linear system of equations describing mass and energy conservation laws. Nonetheless, it has been recently proved that the usually adopted representation of distributed pipe demands as lumped withdrawals at ending nodes causes inconsistent calibration results and pipe head loss errors which could be non negligible in some network conditions. The original GGA has been contextually modified by introducing a correction of pipe hydraulic resistance under the assumptions of a friction factor independent from the flow regime. This paper aims at providing researchers and software developers with a general formulation of the GGA which entails both the adoption of any generic monomial head loss formula and pipe hydraulic resistance dependence on flow regime. The results could be easily extended to other methods of network analysis.