Modeling in Complex Large-Scale Topologies Applied to Urban Water Systems

Abstract

The increasing frequency of extreme rainfall events and the growing reliance on underground conveyance infrastructure have heightened the need for reliable simulation tools that can capture rapid pressurization and mixed‐flow dynamics in urban water networks. This dissertation advances the state of the art in one‐dimensional hydraulic modeling by addressing two complementary problems: (1) accurately representing air-phase interactions during transient filling in complex, large‐scale stormwater tunnels and intermittent drinking‐water supply systems; and (2) integrating air‐phase compressibility into the existing solver SWMM without prohibitive computational cost and version constraints. Chapter 1 presents the introduction and objectives of the dissertation. In Chapter 2, an idealized stormwater collection networks (SCNs) with dendritic and looped topologies are subjected to uniform rainfall in EPA SWMM 5.1 to characterize pressurization onset and propagation. Eight nondimensional flow indices (NDFIs) are introduced to quantify system responses across conduit slopes, roughness, and rainfall rates, providing a framework for system‐wide vulnerability assessment. Looped networks are recommended over dendritic, as the results indicate more resiliency of looped topologies to systemwide pressurization due to flow spread out. In Chapter 3, SWMM’s algorithms (EXTRAN, Preissmann slot, and custom high‐celerity slots) are benchmarked using the Richmond Transport Tunnel, to incorporate the effects of complex geometries with an abrupt discontinuity of 4.27 m to 1.07 m in diameter. Three spatial discretizations and eight Courant‐based time steps are systematically varied and compared against a finite‐volume HAST solver. Continuity errors and Nash–Sutcliffe efficiencies reveal the limitations of standard SWMM implementations at abrupt geometry changes. The DxD10 spatial algorithm coupled with a time step that yields a Courant condition close to unity are recommended, along with the SWMM’s standard Preissmann slot algorithm. Results also indicate that the Sjöberg’s transition reduced the numerical instabilities of the slot algorithms, agreeing with the literature. The study presented in Chapter 4 introduces a methodology to estimate systemwide air pressure in complex topologies using EPANET. Controlled experiments on a looped laboratory network simulate water‐supply priming were conducted. An adapted emitter formulation is proposed to simulate air pressure behavior under filling conditions using EPANET up to the slamming of water against the ventilation points. Results indicate that limiting the inflow rates into the system are recommended to prevent excessive pressure pulses from water hammering regardless of ventilation. Results also indicated a reasonable agreement between measured and modeled air pressure; however, caution must be taken when extrapolating these results to a real scenario. Finally, in Chapter 5, Surge-SWMM model is introduced, a model under development that couples SWMM’s dynamic‐wave hydraulics with a polytropic air‐phase model proposed by Zhou et al. (2002). By coupling these two models, Surge-SWMM retains SWMM’s computational efficiency while capturing air compressibility effects. Benchmarks on single pipe filling scenarios demonstrate the feasibility of the approach. Collectively, this work potentially delivers a new methodology and a software framework for pipe filling modeling in urban drainage and distribution networks.