Abstract

For several ailing water distribution networks in the world, during conditions of excessive withdrawals or insufficient water production, pressures fall to very low or even negligible values and consequently, no water can be supplied. Usually, most pipes have water which either fills or nearly fills their cross sectional areas but the pressure to push it out is absent. With conditions changing from pressurized to no pressure (free surface flow), existing water supply models are unable to simulate either free surface flow or the transition between free surface to pressurized flow. In this study, transient “low pressure-open-channel flow” (LPOCF) conditions were analyzed. The interest of this research lies in the coexistence of free surface and pressurized flow regimes with the aim of understanding the pressurization process of pipes. This was represented by a flow regime transition from free surface to pressurized flow through a moving interface along the pipeline. Results revealed the merits of applying full dynamic wave equations in the solution of transient LPOCF conditions in water distribution networks.

Key words: Free surface flow, full dynamic equations, low pressures, open channel flow, pressurization, water supply, flow regime transition, mixed flow.