Building A Sewer Network Model Using NewC Scheme
Date Issued
2007
Date
2007
Author(s)
Su, Yu-Hao
DOI
zh-TW
Abstract
The first part of this study develops a one-dimensional storm sewer model with NewC scheme (Kutija and Hewett, 2002). It designs a control volume containing one manhole and all the connected half-length pipes and bases on volume-integrated water volume and the discharges through control surface. Given that free surface exists in manholes and that manholes can be considered as the Preissmann-slot applied to pressurized pipe flow, the de St. Venant Equation can be applied to solve both open channel as well as surcharge flow. The NewC scheme is adopted for it’s ability to simulate trans-critical flow with unconditionally stability. Unsteady case studies demonstrate that the model can stably simulate flows under both full and non-full conditions. Compare its output to that of SWMM, the differences of stages and discharges are all within 1%.
The second part devices an efficient algorithm to disjoin solution of sewer network into solving a collection of 1D sewer pipes and simultaneous equations of junctions. The algorithm of Sen and Garg (2002), which utilized non-staggered grid and Preissmann four point scheme, is adapted to the numeric scheme of NewC. Comparing to the continuity equation of junctions, the sign convention to assemble 1D sewer pipes is defined. The algorithm consists of three parts. (1) Use the first sweep of a double-sweep method to transform the tri-diagonal coefficient matrix into a bi-diagonal one. (2) Apply Gauss Elimination to decouple internal state variables from those at external boundaries or internal boundaries, i.e., junctions. The equations of junctions consist of 2 equations derived from each 1D sewer as well as 1 junction or boundary equation at each end. A total of 4N unknowns for N 1D sewer pipes are solved simultaneously. (3) Employ the double-sweep algorithm to solve for the internal state variables of each 1D sewer pipe with known boundary state variables. A Y-shape and a loop sewer network is designed to test the algorithm. The simulations prove the algorithm is stable and efficient.
The third part of this research is to couple the sewer network flow model with the open channel flow model of urban street network. We adopt Villemonte’s formula for submerged weir flow to compute the interchange discharge or lateral flow between sewer system and street flow. The lateral flow is based on the water levels of manholes and those of street flow. Through designed case studies, the coupled model smoothly and accurately simulates the street and sewer flow.
Subjects
迪聖凡南方程式
NewC法
明渠流
滿管流
下水道
管網
市街流
耦合
de St
Venant Equation
NewC scheme
Open channel flow
Surcharge flow
Sewer Network
Overland flow
Coupling.
Type
thesis
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