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Showing posts from March, 2010

Steady State Option in SWMM 5

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The skip steady state periods uses the last computed flows in the conveyance system instead of computing new flows. In the sample graphs you can see where the change in lateral flow is below 0.05 cfs (the blue arrow in the second image). The network solution used the steady flows about 27 percent of the time. The time step summary in the text output file tells you how often the model was in steady state.

Skip Steady State Periods
Checking this option will make the simulation use the most recently computed conveyance system flows during a steady state period instead of computing a new flow routing solution. A time step is considered to be in steady state if the change in external inflow at each node is below 0.5 cfs and the relative difference between total system inflow and outflow is below 5%.

Lead and Lag Pump Options in SWMM 5

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Introduction: If you have a lead and lag pump connecting the same upstream and downstream nodes the normal behavior for the two pumps is to have the the lead pump turn on first followed by the lag pump. The turn on and turn off depths for the pumps determine when the pumps turn of. The pump will work as a simple lead and lag pump based on a wet well elevation without any real time controls.



If you want to add real time controls (RTC) to the lead and lag pumps you can add more sophisticated controls. For example, if you wanted to turn on and off the lead pump at successive time steps then you can add these RTC rules
; New Real Time Control (RTC) Rules RULE RULE-1 IF PUMP LEAD_PUMP STATUS = ON AND PUMP LAG_PUMP STATUS = ON THEN PUMP LEAD_PUMP STATUS = OFF PRIORITY 1.000000
RULE RULE-2 IF PUMP LEAD_PUMP STATUS = OFF AND PUMP LAG_PUMP STATUS = ON THEN PUMP LEAD_PUMP STATUS = ON PRIORITY 1.000000
RULE RULE-3 IF PUMP LEAD_PUMP STATUS = OFF AND PUMP LAG_PUMP STATUS = ON THEN PUMP LEAD_PUMP STATUS = ON PRIORI…