How to Make a Break Node in SWMM5 and InfoSWMM for Force Mains with Emojis

🔍 The central issue being highlighted is ensuring Force Mains are kept full (or d/D equal to 1) when the pumps activate. Achieving this in SWMM 5 can be a challenge due to its single Q link solution, compared to the 4 or more flow points in the IWCS solution. 🔄 There have been past suggestions to add a break node at the end of force mains to ensure they remain full. However, this doesn't always work, especially when a gravity main exists at the end of the rising force main. The gravity main instantly takes up the flow from the long force main, keeping the downstream node depth minimal, which results in the force main not being fully filled – leading to customer dissatisfaction. 😤 A potential solution is to amplify the gravity main roughness, simulating the transition from the force main to the gravity main, which keeps the depth elevated and the force main filled most of the time.

📝 Here are the eight suggestions:

1. ⚙️ Use a Flap Gate for the rising main with HW Force Main Coefficients.
2. 🔧 Add a Break Node at the end of your longer Force Mains with a Surcharge Depth using the Insert Manhole Tool.
3. ⛓️ The d/D values for the force main usually being less than 1 is due to the downstream node of the Force Main having a low depth. Adding a Break Node ensures it remains fuller.
4. 🌊 Change the link AFTER the Break Node to a Gravity Main, and increase the roughness n value (2 to 3 times rougher) to simulate the transition losses.
5. 📈 This action will boost the node's depth at the Force Main's downstream end, ensuring it remains full most of the time.
6. 📊 As highlighted, the force main link has a single Q and three depths. The d in the d/D graph is derived from the midpoint depth or the average of the link's upstream and downstream depths.
7. 🚰 In model reality, the force main is always full at the link's upstream end but is affected by the low downstream depth.
8. 🌟 Increasing the roughness in the gravity main makes results align more closely with user expectations for the d/D value, offering a realistic representation.

🌩️ Use a Flap Gate for the rising main with HW Force Main Coefficients.
🌩️ Introduce a Break Node at the end of longer Force Mains with a Surcharge Depth using the Insert Manhole Tool.
🌩️ The typical d/D values for the force main are less than 1 due to the downstream node's low depth. Adding a Break Node ensures it remains fuller.
🌩️ Post the Break Node, change the link to a Gravity Main. Increase the roughness n value for a realistic transition.
🌩️ This ensures the node's depth at the Force Main's downstream end remains high.
🌩️ The force main link has one Q and three depths, with the d in the d/D graph derived from the midpoint depth.
🌩️ In model reality, the force main remains full at the link's upstream end.
🌩️ Increasing the gravity main's roughness offers results that align closely with user expectations and offer a touch of reality.

Advanced Force Main Solution and Gravity Main Attenuation in InfoSewer for better Pump, Force Main, Gravity Main Simulations

This blog is about using the Advanced Force Main Solution and Gravity Main Attenuation in InfoSewer for better Pump, Force Main, Gravity Main Simulations  

1. Select Advanced Force Main Solution and Flow Attenuation the Run Manager
2. The overall Continuity Error will be Better
3. Gravity mains will be closer to the Force Main Flows
4. Force Main Flows will be closer to the Pump flows 

5. Select Advanced Force Main Solution and Flow Attenuation the Run Manager	Force Main Flows will be closer to the Pump flows
   The overall Continuity Error will be Better	Gravity mains will be closer to the Force Main Flows

Advanced Force Main Solution and Gravity Main Attenuation in InfoSewer for better Pump, Force Main, Gravity Main Simulations

One Second View of a Pump Event in InfoSWMM / SWMM5

"Master the dynamics of pump operations in fluid simulations with a one-second timestep 🔍⏱️:

1️⃣ Activation: The pump engages once the Wet Well reaches the predetermined 'Pump On' depth. 2️⃣ Flow Calculation: Leveraging the pump curve, the system calculates the flow based on the differential head across the pump. 3️⃣ Head Gain Adjustment: Post-activation, the head gain begins to decrease due to the elevated flow in the force main and the rising depth at the downstream node. 4️⃣ Stabilization: Shortly after starting, the pump enters a phase of constant flow, stabilized by the steady head gain across the pump. 5️⃣ Initial Surge: Observe a brief spike in flow at the onset of the pump cycle, a result of the rapid shift in pump head gain.

Unlock the nuances of pump behavior with each simulation second, enhancing the precision of your hydraulic models 💦🔄📊."

One Second View of a Pump Event in InfoSWMM / SWMM5

Rules for Force Mains in InfoSewer and H2OMap Sewer

The image at the bottom shows the rules for Force Mains in InfoSewer and H2OMap Sewer:

1.      Gravity Main
2.     Wet Well
3.     Pump
4.     Chamber Manhole
5.     Force Main  if you have many force mains the node BETWEEN two force mains has to be a Chamber Manhole

a.     The error messages for this are now rigorously enforced and they may not  have been in past versions

6.     Loading Manhole
7.     Gravity Main

Hazen Williams and Force Mains in SWMM 5

A few tips for using Hazen Williams and Force Mains in SWMM 5.   A key fact is to remember ONLY one flow in the middle of the link is computed in SWMM 5 so you may have to add Break nodes, use a smaller time step and use a flap gate depending on how often your pumps turn on.  If you do not have numerical problems with the time step you should get exactly the same head loss as you do in steady state Hazen Williams calculators when you use InfoSWMM, H2OMap SWMM and SWMM 5.

Figure 1.  Larger Tip Image 

Figure 2.  SWMM 5 compares well to the Hazen Williams Head loss calculators

How to use the Report Feature of the HGL Plot in InfoSWMM

Subject:   How to use the Report Feature of the HGL Plot in InfoSWMM

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.

SWMM 5, H2OMap SWMM and InfoSWMM Time Step Guide

Subject:    SWMM 5, H2OMap SWMM and InfoSWMM Time Step Guide

If you use a variable time step in SWMM 5 or InfoSWMM/H2OMAP SWMM it is hard to gauge the proper value of the conduit lengthening.  You want to use a value that does not increase the volume of the network yet does increase the length of the shortest links so you can use a longer time step.  A good approximation to the time step that you want to use is shown in the image.  

The Time Step Guide in seconds is Link Length / [Velocity + sqrt(g*Maximum Depth)] with the assumption that the velocity at maximum depth is about the value of the wave celerity for closed links or sqrt(g*Maximum Depth).  Normally (unless pumps are involved) the average time step used during the simulation is a good gauge of the time to use for the simulation.  For example, in this model run the time step used is 13 seconds which is about the conduit lengthening time step of 20 seconds * adjustment factor of 0.75

InfoSWMM and H2OMap SWMM Pump Summary Table

Subject:   InfoSWMM and H2OMap SWMM Pump Summary Table

The Pump Summary Table in Report Manager tells you how often the pumps turn on (Start-Up Count), the percent of the simulation time it was used (Percent Utilized) and the maximum, minimum and average flow for the pumps.

You can also see flows in the downstream links from the pumps in the force mains along with the pumps.

 

If you use the Mixed Graph Control you see the Pump flows and Link Flows on the same Graph

You can control the replay of the HGL Plot by altering the stepping time in Graph Settings

InfoSWMM Report Manager and Field Statistics

Subject:  InfoSWMM Report Manager and Field Statistics

You can also use the mixed graph feature to plot the pump flow and the downstream flows on the same graph.  If you click on the Report command then you can also use aField Statistics command to see the Statistics for each Link and Pump.   The right mouse button for the Report also allows you to make a scatter plot and graph the flows in theforcemains versus the flows in the pumps.  

How to Use the Map Display for the Maximum Adjusted d/D or Maximum q/Q in an EPS InfoSewer Simulation

How to Use the Map Display for the Maximum Adjusted d/D  or Maximum q/Q in an EPS InfoSewer Simulation

You can do a Map Display of the adjusted d/D values (Figure 1)  from the Gravity Main Range Report (Figure 2) to show those pipes that are full thematically.  For example, the links in red in Figure 1 show the effect of the pump blockage and the links in green are those NOT full due to the pump blockage.  You will need to copy the adjusted d/D or the maximum q/Q values from the Range report to the Link Information Table to have some values to Map (Figure 3 and 4).   The maximum adjusted d/D or the Maximum q/Q can be mapped using the new link information (Figure 5).

Figure 1  Map Display of the Maximum Adjusted d/D from the Gravity Range Report.

Figure 2.   Maximum Adjusted d/D or Maximum q/Q can be copied from the EPS Range Gravity Main Report.

Figure 3.  Create a new variable In the Link Information Table.

Figure 4.  New variables for the Map Display from the Range Report in the Pipe Information Tables for Each Link.

Figure 5.  Link Information new Parameters of Variables can be used to Display the maximum d/D or q/Q during the EPS simulation.

How Does a TYPE1 Pump Work in SWMM 5?

Subject:   How Does a TYPE1 Pump Work in SWMM 5?

A SWMM 5 Type1 pump is called an offline pump but the name comes from SWMM 4 and the Pump is controlled by volume instead of depth or head as in the SWMM 5 TYPE2, TYPE3 and TYPE4 Pumps.  The attached example SWMM 5 model has an offline storage node that pumps flow INTO the Offline Storage unit during high flow and FROM the Offline Storage Unit during low flow.  The SWMM 5 Real Time Control (RTC) rules determine which of the two pumps operate based on the flow in an upstream link (Figure 1). 

Figure 1.   RTC Rules and Schematic of an OffLine Pump in SWMM 5.

InfoSewer By Discharge Control for a PUMP

InfoSewer By Discharge Control for a PUMP

You can control the pumps in InfoSewer and H2OMap Sewer by using a Pump Control which will control the pump based on:

1.       Volume
2.      Level
3.      Discharge
4.      Inflow
5.      Time

If you use a By Discharge control the pump speed of the pump is increased or decreased to pump the incoming Wet Well flow based on the pump rules and the geometry of the Wet Well (Figure 1).

Figure 1.  By Discharge Control for  PUMP in InfoSewer and H2OMAP Sewer will change the Pump Speed of the pump to follow the Base Pump Flow Rules.

InfoSewer Inflow Control for a PUMP

InfoSewer Inflow Control for a PUMP

You can control the pumps in InfoSewer and H2OMap Sewer by using a Pump Control which will control the pump based on:

1.       Volume
2.      Level
3.      Discharge
4.      Inflow
5.      Time

If you use a By Inflow control the pump speed of the pump is increased or decreased to make the Upstream Wet Well Level Constant (Figure 1).

Figure 1.  Inflow Control for  PUMP in InfoSewer and H2OMAP Sewer will change the Pump Speed of the pump to make the Wet Well level constant

InfoSewer to InfoSWMM Import Tips

Subject:   InfoSewer to InfoSWMM Import Tips

The direct import of InfoSewer to InfoSWMM (Figure 1) is both direct and robust but you need to be aware of Run Manager changes to optimize the InfoSWMMmodel:

1. Make sure that the Flow Units in InfoSWMM Run Manager match the default flow units in InfoSewer so that the DWF values are comparable,
2. Make sure that the Output Flow Units in InfoSWMM match the Output Flow Units in InfoSewer so direct comparisons are easier,
3. Add a Pump On and Pump Off depth to the Pumps in InfoSWMM so that the pumps work better in a fully dynamic solution,
4. The Fixed Pump Curves of InfoSewer should be checked in the Pump Curve section of InfoSWMM to make sure they are comparable,
5. The InfoSWMM conduit step lengthening option should be used to speed up the model if you have short links in InfoSewer,
6. You can check the overall balance in the two modeling platforms by comparing the System Load Graph in InfoSewer to the Total Inflow Graph inInfoSWMM.

Figure 1   Dialog for Importing InfoSewer to InfoSWMM

Example FM SWMM 5 model with and without Surcharge Depth

Subject:   Example FM SWMM 5 model with and without Surcharge Depth

You need to use the surcharge depth for a Force Main in SWMM 5 to allow the engine to find the right point on the pump curve and pump up the rising main.  If you do not use a surcharge depth then the flow MAY be very small in the rising main due to a small head difference.  Of course the flow in the force main depends on the pump curve you have entered but having the right downstream head of depth for the link matter as well.  The attached model was created in SWMM 5.0.022 

Force Main Friction Loss in InfoSWMM and the Transition from Partial to Full Flow

Subject:  Force Main Friction Loss in InfoSWMM and the Transition from Partial to Full Flow

You can model Force Main friction loss in InfoSWMM using either Darcy Weisbach or Hazen Williams as the full pipe friction loss method (see Figure 1 for the internal definition of full flow).   A function called ForceMain in InfoSWMM whose purpose is to compute the Darcy-Weisbach friction factor for a force main using the Swamee and Jain approximation to the Colebrook-White equation .  No matter which method you use for full flow the  program will use Manning's equation to calculate the loss in the link when the link is not full (see Figure 2 for the equations used for calculating the friction loss – variable dq1 in the St Venant equation for InfoSWMM).   The regions for the different friction loss equations are shown in Figure 3.    

There is no slot in InfoSWMM for the full pipe flow as a surcharged node in InfoSWMM uses this point iteration equation (Figure 4): 

dY/dt = dQ / The sum of the Connecting Link values of  dQ/dH 

where Y is the depth in the node, dt is the time step, H is the head across the link (downstream – upstream), dQ is the net inflow into the node and dQ/dH is the derivative with respect to H of the link  St Venant equation.  If you are trying to calibrate the surcharged node depth, the main calibration variables are the time step and the link  roughness:

 1.   Mannings's N

2.   Hazen-Williams or

3.   Darcy-Weisbach 

The link roughness is part of the term dq1 in the St Venant solution and the other loss terms are included in the term dq5.  You can adjust the roughness of the surcharged link  to affect the node surcharge depth.   The point iteration continues until the sum of the flow in the node is zero – basically the new depth in the node either increases or decreases the friction loss in the force main so that net flow at the node is zero.  This is why it is important to use the right time step to ensure that the net flow is zero when the pumps turn on and off. 

Figure 1.  How the full pipe condition is defined in InfoSWMM - both ends have to be full

Figure 2:  Friction equations used in SWMM 5 for a Force Main. Figure 3:  Regions of Friction loss equations in SWMM 5.

Figure 4.  The Node Surcharge Equation is a function of the net inflow and the sum of the term dQ/dH in all connecting links. Generally, as you increase the roughness the value of dQ/dH increases and the denominator of the term dY/dt = dQ/dQdH increases.