SWMM5+ Status and Future Plans

The SWMM5+ parallel finite-volume hydraulic solver was released to the public in 2023. This presentation will discuss the current capabilities of the solver, its performance relative to EPA SWMM, and limitations/problems that users might experience. The new solver uses a finite-volume approach with sub-discretization of network links based on the user's choice of a nominal (target) element length. At a minimum, each link of an EPA SWMM system must be broken up into three sub-elements to capture hydraulic transitions between junctions. The SWMM5+ solver is stable and mass conservative to machine precision but shows some unphysical junction oscillations --- typically in the last stages of drawdown when flows are small. A major advance in the SWMM5+ solver is a new Dynamic Preissmann Slot (DPS) algorithm that is smooth and stable while providing users direct control over the celerity of a pressure wave in a surcharged pipe. For small to medium size systems, the SWMM5+ solver is noticeably slower than EPA SWMM. Testing is presently underway for simulating large parallel systems, where SWMM5+ should be more efficient.

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