Ability of software SWMM to simulate sewer smooth pressurization transient

As a consequence of heavy rainfall events or network malfunctioning, filling of sewers (pressurization) and network overflowing may occur. Several models are commonly used to simulate floods in drainage networks and their results are usually thought to be reliable and robust. Actually, mathematical models based on the momentum equation appear to be more suitable in correctly simulating the pressurization moving jump but models based on the energy equation are much more popular because of their greater simplicity in comparison to the former ones. In this paper, on the basis of laboratory pipe tests, the ability of software SWMM (Storm Water Management Model, probably the most popular software for drainage networks) to simulate transient pressurization is studied. Many numerical tests were carried out by SWMM varying the spatial and time steps as well as the Preissmann slot width in order to examine the performances of the software along even wider intervals of these parameters than usual in practical applications. The comparison between simulated and experimental surges allows one to draw interesting conclusions on the effectiveness of SWMM in simulating pressurization as well as on the choice of the parameters themselves.