Pre 2014 Blogs

Here is one way to model multiple pumps between the same downstream and upstream nodes using the pump curves and the Real Time Control Rules (RTC) in SWMM 5.  Here are the steps:

1.   Enter the data for three pumps in the browser by using the Add Pump Icon

2.   Enter three Pump Head/Flow Curves so that the 2^nd and 3^rd Pump Curves are the sum of the flows in the 1^st and 2^nd Pumps together and the sum of the flows in the 1^st, 2^nd and 3^rd respectively for the 2^nd and 3^rd Pump Curves

3.   Enter a RTC Rule in the Control Editor so that when the 1^st Pump is turned on – the 2^nd and 3^rd Pump is turned off

4.   Enter a RTC Rule in the Control Editor so that when the 2^nd  Pump is turned on – the 1^st  and 3^rd Pump is turned off

5.   Enter a RTC Rule in the Control Editor so that when the 3^rd  Pump is turned on – the 1^st and 2^nd Pump is turned off

Using these rules you can see that for the 1^st Pump turns on when the Node WetWell has a depth below 2 feet, the 2^nd Pump turns on when the Node is between a depth of 2 to 5 feet and the 3^rd Pump turns on when the Node Depth is above 5 feet.

RULE Pump1

IF Node WetWell Depth <= 2

THEN PUMP PUMP2 STATUS = OFF

AND PUMP PUMP3 STATUS = OFF

Priority 1

RULE Pump2

IF Node WetWell Depth > 2

AND Node WetWell Depth <= 5

THEN PUMP PUMP1 STATUS = OFF

AND PUMP PUMP3 STATUS = OFF

Priority 2

RULE Pump3

IF Node WetWell Depth > 5

THEN PUMP PUMP1 STATUS = OFF

AND PUMP PUMP2 STATUS = OFF

Priority 3

The entrance, exit and other losses in SWMM 5 are computed at the upstream, downstream and midpoint of the sections of the link.  However, if the normal flow equation is used for the link during a time step then these losses are zero as the flow in the link is based solely on the upstream area and upstream hydraulic radius of the link.   If you add loss coefficients and the normal flow equation is used then you will not see any change in the flow as you modify the loss coefficients.

St. Venant equation – this is the link attribute data used when the St. Venant Equation is used in SWMM 5.  Simulated Parameters from the upstream, midpoint and downstream sections of the link are used.

Normal Flow Equation – this is the link attribute data used when the Normal Flow Equation is used in SWMM 5. Only simulated parameters from the upstream end of the link are used if the normal flow equation is used for the time step.

I saw this on the Daily Dish, http://andrewsullivan.thedailybeast.com/2011/07/roo.html, it is an extremely green roof but a roof that can be simulated in SWMM 5.  You simulated it as a Bio Retention Cell with a Surface, Soil, Storage and an Underdrain to the Gutters of the roof.  You can also have a rain barrel connected to the gutters to storage and drain the rainfall. 

If you use a weir in SWMM 5 then two flow equations are used

1.       The weir uses the weir flow equation when the head at the weir is between the invert elevation of the weir and the crown of the weir and

 2.      An orifice equation when the head is above the weir crown or the weir is submerged.

If you are using Non linear Reservoir Modeling in SWMM 5 there are

1.   Five parameters for Horton Infiltration,

2.   Three parameters for Green-Ampt and

3.   Two parameters for CN infiltration, one parameter (conductivity) has been deprecated by the EPA in SWMM 5.   The Drying Time is used to regenerate the Infiltration Rate for continuous simulation.  Only two parameters are now used for CN infiltration:  The CN value itself and the drying time.

The dynamic wave flow in SWMM5 and InfoSWMM is calculated from the following equation

Q  =   (Qold – dq2 + dq3*sigma +  dq4*sigma ) / ( 1  + dq1 + dq5)

Where,

Qold               =         Last Time Step Flow in the Link

dq1                 =         friction loss term

dq2                 =         water suface slope + bed slope term

dq3                 =         midpoint area non linear term

dq4                 =         upstream and downstream area non linear term

dq5                 =         Entrance, Other and Exit Loss Term

sigma            =         function of the Froude number and a function of the Three Intertial Term Options

Figure 1 shows how Sigma is set based on the user selection of the Three Intertial Terms.  Figure 2 shows how Sigma is calculated for the Dampen Option.  If you use Ignore then dq3 and dq4 are ignored all of the time, if you use Dampen then dq3 and dq4 are used for a Froude number less than 0.5 and then the terms gradually fade away until a Froude number of 1 is reached.   If you use Keep then the non linear terms are used all of the time no matter the value of the link Froude Number.  There is one exception to this rule: If a closed link is full then the value of sigma is set to 0.0 no matter what is selected for the Intertial Term.

Figure 1.  The value of Sigma for each of the Three Inertial Term Options in SWMM 5 and InfoSWMM/H2OMAP SWMM

Figure 2.  At each iteration for each link during the simulation the link Froude Number is calculated and based on the Froude Number the value of Sigma is Set.

The EPA Web Site has three manuals that you can download at http://www.epa.gov/nrmrl/wswrd/wq/models/swmm/#Downloads

1.   SWMM Applications Manual

2.   SWMM 5 Quality Assurance Report

3.   SWMM 5 Users Manual

The process is easy if you use Domain and Facilities.  

Step 1.  Use the Trace Upstream Network Command in Utilities to find the upstream network from your node of interest.  The upstream network is saved to a Domain.

Step 2.  Use the Facility Manager to 1^st deactivate the whole network and then 2^nd to add the Domain to your Facility or the nodes and links that you will simulate

You now have a smaller network to examine in Detail.  You may have to make a temporary Outfall node to run the model if there are no Outfalls in the model.

Dry weather flow can be added to any node in SWMM 5.  The dry weather flow is computed as the average flow * the monthly pattern * the daily pattern * hourly pattern * the weekend daily pattern to give the Dry Weather Flow at any time step (Figure 1).   Since the four types of patterns (Figure 2) are all multiplied together then for Saturday and Sunday the hourly pattern and the weekend hourly pattern will both be used.   This will have the effect of overestimating the flow if the multipliers are greater than 1 and underestimating the flow if the multipliers are less than one.  You should enter the  Pattern X for the Weekend Hourly Pattern in SWMM 5  where

X  = Weekend Hourly Pattern / Hourly Pattern

So that when the pattern X is multiplied by the Hourly Pattern the program will use the intended Weekend Pattern.

Figure 1.  How Dry Weather Flow is Computed in SWMM 5

Figure 2.  The Four Types of Time Patterns in SWMM 5.0.022

The report feature of the HGL plot helps you understand in more detail the pump flows, forcemain flows and node heads.

Step 1. Load the Domain in the HGL Plot using Report Manager

Step 2. Click on the Report Command to Show the HGL Data in Tabular Format

Step 3.  Format the Results Table from the HGL Plot to see the data better.

Step 4.  Now we have the heads, flows and velocities for the pumps, nodes and force main links in our Domain around the pump of interest at time steps of 2 seconds,  We can now see how the flows, heads and velocities change downstream from the pump.

Step 5.  Force Mains, Nodes and Pumps in our Table

Step 6.  The pump turns on and the flow moves downstream to the force mains – the heads in the nodes increase to balance the flow at each node.  As you can see there is a 1 to 2 GPM decrease due to attenuation as the flow from the pump moves into the force mains.

Step 7.  The pump turns off and flows downstream decrease.  You can get negative flow if the downstream head is higher than the upstream head of the link.

Step 8.  Use Advanced Labeling and the HGL Plot Stepping Interval to see all of the data in your Plot.

If you want to save the output at a small report time step (2 seconds in this case) and you have a long simulation or large model then the reading of the graphicalo results may not be as speedy as you want.  You can save ONLY the DOMAIN to the output binary file however to make this smaller and faster to react.

Step 1.  Define your Reporting Time Step and Your Routing Time Step.  In this case we are routing at 1 second but saving the DOMAIN results every 2 seconds.

Step 2.  Clear your existing DOMAIN and Create a DOMAIN based on the area you are most interested in during the simulation.

Step 3.  Use the Advanced Tab in Run Manager and select Domain as the Output Scope – this will save only the Domain to the output binary file.

Step 4.  Run the simulation using Run Manager and then look at the output.  You are restricted to 8800 graph points but the number of points in the Report Table is unlimited.

Step 5. You can use the Data Plot Option (right mouse click) to see a subset of the larger than 8800 data points.

If you have a fixed boundary outfall condition in your model and want to prevent reverse flow when you run your simulation the best way is to use the Hot Start files to fill up the links and nodes at the start of the simulation.

1^st Step:  Turn off the DWF inflow so that ONLY the flow from outfall enters the network.  Use the Process Models in Run Manager to turn off and turn on the Dry Weather flow.

2nd Step:  Run the simulation first SAVING a Hot Start File using zero initial node depths and link flows.

3rd Step:  Save and Use Hot Start Files until the initial and final volume in your Network stays the same. 

4th Step:  Check the Initial and Final Stored Volume in the output text file

5th Step:  Check to see if you nodes are stable by using a Junction Group Graph

6th Step:  Now Run the Simulation with flows turned an and the network will start out with the Boundary Condition depths and stable flows

This Database Query (DB) will find all loading Manholes with a Load1 and a Load2 greater than 0.  InfoSewer has up to ten possible loads in a Manhole.  You can use the DB Query (Figure 1) to create a Query Report to show all of the Manholes with a non zero loading for both Load1 and Load2.  New Queries can be made to show any combination of the ten Manhole Loadings either by altering the DB Query or creating a new DB Query.

Figure 1. DB Query to find Manholes with Load1 and Load2 greater than 0.0 

Figure 2.  Query Report for the DB Query