Surge Modeling in Sewers using the Transient Analysis Program (TAP)
This chapter presents a new type of computational hydraulics program that is appropriate for simulating rapidly-varying transients (e.g. surges) in sewers. The hydraulics program was validated using experimental surge data in a pipeline obtained in a hydraulics laboratory. The validation data are presented along with two case study applications for the program.
The Transient Analysis Program (TAP) is a state-of-the-art computational hydraulics program that was developed to simulate steady-state, gradual time varying, and rapidly-varying flow conditions in a system of channels/conduits. TAP properly simulates the one-dimensional open channel, transitional and pressurized wave fronts that result from opening/closing gates, turning pumps ON/OFF, raising/lowering of inflatable dams and rapid filling. TAP was developed because the existing available computational programs commonly used for simulating sewer system hydraulics (e.g. EPA-SWMM, XP-SWMM, MOUSE and InfoWorks) do not properly represent the wave fronts and the resulting surges that are of concern during these situations.
TAP has been used to evaluate sanitary and combined sewer systems, CSO control facilities including capture and flow-through tunnel systems, and storm drains. Conduits with diameters that range from 4 inches to 40 feet have been modeled with TAP. TAP is especially useful in analyzing deep relief sewers and tunnels. Rapid filling of these systems can result in the transitions from open channel to pressurized conditions with the creation of hydraulic bores. These hydraulic bores have steep wave fronts and can create surges in the hydraulic grade line (HGL) that rise above ground surface elevations. Surges are important to evaluate and control in deep relief sewers and tunnels since they can cause high internal pressures that can stress the conduit walls, and rise to grade and damage manholes, pavement and surface structures.
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