Evaluating SWMM capabilities to simulate closed pipe transients

Abstract

One of the most used 1D tools to model collection systems is the Storm Water Management Model (SWMM). Solving the full form of the Saint Venant equations, this model represents typical unsteady flow conditions in sewer systems. However, it may be insufficient to address fast transient flow conditions that can be present during extreme events or unscheduled operational conditions. SWMM version 5.1.013 was implemented the Preissmann slot as an alternative method to handle pressurization. To date, no studies were found analysing the applicability of SWMM to represent closed-pipe fast transient flows applying the Preissmann slot pressurization algorithm. Therefore, the present work investigates the ability to model different fast transients conditions in SWMM under various spatial and temporal discretizations along with variations in the Preissmann slot algorithm. Using an alternative implementation of the SLOT pressurization algorithm, along with artificial spatial discretization and routing time-steps estimated by the Courant stability condition, it is shown that SWMM is capable to perform satisfactory certain types of closed pipe transient simulations.

Keywords:

• Dynamic flows
• Preissmann slot
• stormwater systems
• SWMM
• transients
• waterhammer

Notation

$A$	=	cross-sectional area (m2)
$\mathrm{B}$	=	slot width (m)
$c$	=	celerity (m s−2)
$C_r$	=	Courant Number (−)
$D$	=	conduit diameter (m)
$g$	=	gravity acceleration (m s−2)
$H$	=	hydraulic head (m)
$h_L$	=	local energy loss per unit length of conduit (–)
$H_o$	=	static water level (m)
$H_{sim}$	=	simulated head change (m)
$L$	=	conduit length (m)
$L2$	=	L2 norm (−)
$Q$	=	flow rate (m3 s−2)
$S_f$	=	friction slope (−)
$V$	=	velocity (m s−1)
$t$	=	time (s)
$x$	=	distance (m)
$\mathrm{\Delta }H$	=	magnitude of pressure wave (m)
$\mathrm{\Delta }{H}_{anl}$	=	analytical instantaneous head change (m)
$\mathrm{\Delta }{H}_{anl}^{\ast }$	=	normalized analytical head change (−)
$\mathrm{\Delta }{H}_{sim}^{\ast }$	=	normalized simulated head change (−)
$\mathrm{\Delta }V$	=	instantaneous change of flow velocity (m s−1)
$\mathrm{\Delta }t$	=	temporal discretization (s)
$\mathrm{\Delta }x$	=	spatial discretization (m)

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.