Hydraulic Modeling of Water Distribution Systems Grady Hillhouse M. Eng. Water Resources Engineering Texas A&M University

Introduction A large percentage of EWB projects involve water. Many of these project include a transmission or distribution component. A basic understanding of pressure conduit hydraulics is essential when designing water infrastructure. In situations where solving pipe networks is too complex, modeling becomes necessary.

Outline Introduction to pressure conduit hydraulics Introduction to EPA NET Basics of Modeling Only an introduction If you have questions, ask!

Pressure Conduit Hydraulics Summed up in two equations: constant

Head Loss Darcy-Weisbach head loss equation

Head Loss (cont.)

Pipe Networks Demand

Solving Pipe Networks Continuity at nodes

Solving Pipe Networks Fixed grade node paths

Solving Pipe Networks Loop Equations

Hydraulic Grade Line Total energy less velocity head

EPANET Public domain (free!) Relatively simple Uses the gradient method to solve pipe networks for flows and pressures.

Components in Models Node – junction between other model elements. Can have external demands. Pipe – convey water between nodes. Reservoir – infinite source of water with a constant or periodically changing water surface elevation. Tank – stores water . Water surface is at atmospheric pressure. Pumps – impart energy to water Valves – various methods of controlling flow or pressure

Skeletonization Depending on the complexity of the system you’re modeling, in may benefit you to simplify the model.

What you provide the model Layout and parameters of infrastructure Demands Initial conditions

What the model provides for you Flow rates in pipes and tanks Pressures at nodes

Examples

Final Notes A model is only as good as the input data you provide. Reference the user’s manual! Never ask the model to do something you don’t understand. Always verify results by checking with hand calculations. Questions?