Users select one (steady-state) time-step from an existing real-time hydraulic simulation, as the starting conditions for
the user's specified transient event (e.g. power failure).
A transient hydraulic simulation covers a user-defined duration. An acceptable duration is limited by:
- the time taken for the system to reach the stable conditions, representing the target steady-state; and
- the amount of free disk space available on the computer.
Long transient simulations at sub-second calculation intervals, can rapidly create output files that are many gigabytes in size.
During a transient simulation:
The Method of Characteristics computes the response as the system transitions from the prevailing steady-state to a new steady-state;
- time steps forward at a user-defined interval, which can be a small as one 100,000th of a second;
- demand from junctions on the system vary with the available
- autonomous, in-line devices such as pressure reducing valves, operate to match current hydraulic conditions;
- in-line valves and pumps operate to match user-defined, time-based changes in valve position or pump speed;
- surge-protection devices (such as air valves, surge tanks, pressure vessels) operate to match current hydraulic conditions;
- result reports are created at user-defined intervals (e.g. 5 seconds), with changes in device state reported in-between;
- maximum and minimum values for all locations and devices are records at every time step; and
- performance parameters for all components are graphed at a user-defined frequency (i.e. each Nth time step). This filtering improves
on-screen display performance.