| From municipal water supply to wastewater collection, pressurized pipe networks form the basis of many urban water systems. Numerical models are essential for analyzing their unsteady hydraulics, but there are multiple types of models with poorly understood ranges of applicability. Water hammer models feature greater physical accuracy, making them suitable for highly dynamic conditions. They are, however, more computationally demanding than the simpler yet less accurate rigid water column (RWC) and quasi-steady models. Unsteady hydraulic analyses require solution methods that are both physically accurate and computationally efficient; accordingly, there is an accuracy-efficiency trade-off. To balance these competing demands, this thesis presents an adaptive hybrid transient model (AHTM) capable of simulating the full range one-dimensional unsteady pipe network hydraulics.;In developing the comprehensive AHTM, a number of gaps in the literature are addressed. A novel RWC formulation is first proposed, one that overcomes the numerical challenges of previous published work. This is subsequently combined with unsteady flow characterization indices and an adaptive scheme to form an incompressible flow AHTM. Essentially, a more demanding yet more physically accurate model is used only when necessary for efficiency; though powerful, the framework does not consider unsteady-compressible flow. The third objective concerns models for such conditions. A flexible water hammer formulation is introduced that generalizes the method of characteristics and the wave characteristics method, two predominant numerical approaches. Finally, the culmination of this thesis combines each of the aforementioned into a single comprehensive, flexible, and efficient AHTM. The AHTM is shown to adapt to the degree of unsteadiness and, more importantly, individual analyses.;Results of this work ultimately benefit practical analyses of unsteady pipe network hydraulics. Not only can simulations be performed more efficiently, but they may encompass multiple transient flow regimes. Moreover, the key advantages of the comprehensive AHTM are its generality and adaptability. |
