With respect to timing, there should be close agreement between the computed and measured periods of the system, regardless of what flow-control operation initiated the transient. With a well-calibrated model of the system, it is possible to use the model in the operational control of the system and anticipate the effects of specific flow-control operations. This requires field measurements to quantify your system’s pressure-wave speed and friction, with the following considerations:

• Field measurements can clearly indicate the evolution of the transient. The pressure-wave speed for a pipe with typical material and bedding can be determined if the period of the transient (4 L/a) and the length (L) between measurement locations is known. If there is air in the system, the measured wave speed may be much lower than the theoretical speed.
• If friction is significant in a system, real-world transients attenuate faster than the numerical simulation, particularly during longer time periods (t > 2 L/a). Poor friction representation does not explain lack of agreement with an initial transient pulse.

In general, if model peaks arrive at the wrong time, the wave speed must be adjusted. If model peaks have the wrong shape, the description of the control event (pump shutdown or valve closure) should be adjusted. If the transient dies off too quickly or slowly in the model, the friction losses must be adjusted. If there are secondary peaks, important loops and diversions may need to be included in the model.