Data Requirements and Boundary Conditions

The data requirements of hydraulic models increase with the complexity of the phenomena being simulated. A steady-state model's simple dataset and system representation are sufficient to determine whether the network can supply enough water to meet a certain average demand. An extended-period simulation (EPS) model requires additional data, but it can indicate whether the system can provide an acceptable level of service over a period of minutes, hours, or days. EPS models can also be used for energy-consumption studies and water-quality modeling.

Data requirements for hydraulic transient simulations are greater than for EPS or steady-state runs. In addition to the information required by a steady-state model, you also need to determine the following:

Pipe elasticity (i.e., pressure wave speed)
The fluid's vaporization limit (i.e., vapor pressure)
The pumps' combined pump and motor inertia and controlled ramp times, if any.
Pump or pump-turbine characteristics for hydropower systems.
The valves' controlled operating times and their stroke to discharge coefficient (or open area) relationship.
The characteristics of surge-protection equipment.

You can use simple methods to estimate each of the above parameters, as described elsewhere in this documentation and in the HAMMER software.

Note: If you are analyzing a subsection or skeletonized version of the system, care should be taken when considering how to represent the boundary condition at the connection point. For example if you're analyzing the transient effects in a transmission main only, you will need to consider if the downstream end of the transmission main should be represented as a known hydraulic grade (tank or reservoir) or known outflow (junction with demand or discharge to atmosphere node). It is important to consider the effects of wave reflection, which will be different depending on the boundary condition used. See Wave Reflection and Transmission in Pipelines.