What are the Equations for Weirs in SWMM 5, Part 2?

Subject:   What are the Equations for Weirs in SWMM 5, Part 2?

What are the Equations for Weirs in SWMM 5, Part 2? by dickinsonre Subject:   What are the Equations for Weirs in SWMM 5, Part 2?  There are four types of Weirs in SWMM 5:  Transverse, Sideflow, V Notch and Trapezoidal.   The trapezoidal weir is a combination of the Sideflow and V Notch Weir and the Sideflow acts like a Transverse Weir when the flow is reversed (Figure 1).  The Weirs can have zero, one or two end contractions (Figure 2) and the Weir Length is a function of the Weir Setting and Horizontal Weir Length.  A V Notch weir works as Trapezoidal Weir when the Weir RTC Setting is less than 1.0   Figure 1.   Weir Equations in SWMM 5  Figure 2.   Valid Number of End Contractions   Figure 3.  Weir Length Calculations   via Blogger http://www.swmm5.net/2013/08/what-are-equations-for-we

What are the Equations for Weirs in SWMM 5?

Subject:   What are the Equations for Weirs in SWMM 5?

There are four types of Weirs in SWMM 5:  Transverse, Sideflow, V Notch and Trapezoidal.   The trapezoidal weir is a combination of the Sideflow and V Notch Weir and the Sideflow acts like a Transverse Weir when the flow is reversed (Figure 1).

Figure 1.   Weir Equations in SWMM 5

Weir Equations in SWMM 5

How to Approximate a Timer in the RTC Rules of SWMM 5

Subject:   How to Approximate a Timer in the RTC Rules of SWMM 5

How to Approximate a Timer in the RTC Rules of SWMM 5 by dickinsonre Subject:   How to Approximate a Timer in the RTC Rules of SWMM 5  SWMM 5 does not have a explicit timer in its Real Time Control (RTC) rules but you can approximate it by using a Control Curve as in the attached example model.  The Control Curve will modify the setting of the Weir by the Inflow to the Storage node.  You can have normal weir flow settings based on the invert elevation of the weir and the Surface node water surface elevation but in addition you can control the weir setting by:  1.   Closing the weir when the inflow is low, 2.   Closing the weir by staggered Storage node depth, 3.   Opening the weir gradually when the inflow increases 4.   Closing the weir by a combination of Node Depth IF statements and Control Curve rules  For example, you can have the Weir Setting controlled the Node Depth,  Link Inflow and Node Inflow  simultaneously approximately with the depth and the inflow parameters closing the weir by proxy instead of by time since the closing. via Blogger http://www.swmm5.net/2013/08/how-to-approximate-timer-in-rtc-rules.html

gate_timer.INP Download this file

How to Approximate a Timer in the RTC Rules of SWMM 5.docx Download this file

Node Comparison in InfoSWMM and InfoSewer

Node Comparison in InfoSWMM and InfoSewer by dickinsonre Note:  Node Comparison in InfoSWMM and InfoSewer  1)    Is there an option to set the manhole sealing method (i.e. locked  or unlocked) in InfoSWMM?  You set the Surcharged depth to a positive value to prevent flooding and keep the pipes under pressure.  You will still have flooding once the water surface elevation reaches the maximum depth + surcharge depth.  Unlike inInfoSewer the depths are not unlimited.  2)    Is defining manhole diameter in InfoSWMM available?  You can set the default surface area of a node or make it a storagenode.    3)    Does InfoSWMM allow me to create parallel pipes with the same  attributes similar to InfoSewer?  You can set the number of barrels in the attribute browser of DB Editor in InfoSWMM.    4)    Can you please confirm that the only element allowed to leave a  storage unit in InfoSWMM is a pump?  No, this is not true.  You can have a gravity main, orifice or weir leave a storage pond or lake.  5)    Is there a tool to check for pipe diameter discrepancies in  InfoSWMM similar to InfoSewer?  Yes, we have a similar Engineering Review and Network Audit Tools 6)    For load patterns, I do not see an option between stepwise and  continuous in InfoSWMM, or is there?  InfoSWMM really only has stepwise linear DWF pattern though you can have a time series of inflows as well which gives you complete flexibility.  7)    Does InfoSWMM offer modeling I&I using pipe length, pipe surface  area etc… like in InfoSewer?   You can but there in not an easy translation,  You have Rainfall Induced Infiltration at a Node. You can relate this to the pipe length but it is not straightforward.  8)    Is steady state simulation and design simulation available in  InfoSWMM similar to InfoSewer?  You can do Steady State easily but design uses a Genetic Algorithm technique if you have InfoSWMMSuite. via Blogger http://www.swmm5.net/2013/08/node-comparison-in-infoswmm-and.html

SWMM5 Weir Rules, Head Calculations and Weir HGL Plots

Note:  SWMM5 Weir Rules and Head Calculations

This note attempts to explain both how the head upstream and the head downstream of a weir in SWMM 5 is calculated compared to the weir crest elevation and also to explain how the weir is presented in the HGL plot of SWMm 5.  There has been confusion in the past concering how the weir is shown compared to the actual weir calculations.  The node head is calculated obviously at both ends of the weir but the head over the weir is always based on H1-Crest or H2-Crest (Figure 1) and hence the weir should look flat – to the weir the downstream head is important but NOT the downstream node invert so the weir really is flat and should look flat in the HGL Profile across the weir (Figure 2).    The crest elevation is always relative to the upstream node invert elevation NOT the downstream node invert elevaation

Figure 1.  How the Head across a Weir is calculated in SWMM 5

Figure 2.   HGL Profile across a Weir in SWMM 5.0.022.  The black line should be shown flat.

Weir and Orifice Flow Equations for a Weir in SWMM 5 by dickinsonre Note:  Weir and Orifice Flow Equations for a Weir in SWMM 5 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. via Blogger http://www.swmm5.net/2013/08/weir-and-orifice-flow-equations-for.html

Weir and Orifice Flow Equations for a Weir in SWMM 5

Note:  Weir and Orifice Flow Equations for a Weir in SWMM 5

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.

Weir and Orifice Flow Equations for a Weir in SWMM 5 by dickinsonre

Note:  Weir and Orifice Flow Equations for a Weir in SWMM 5

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.

via Blogger http://www.swmm5.net/2013/08/weir-and-orifice-flow-equations-for.html

SWMM 5 Clocktime RTC Rules for Pumps, Weirs and Orifices

Subject:  SWMM 5 Clocktime RTC Rules for Pumps, Weirs and Orifices

You can use the Control or RTC rules in SWMM 5 to adjust the settings of the weirs, pumps and orifices based on the clock time each day of your simulation.  Here is an example that will adjust orifice height every ½ hour for 7 orifices at one time using two sets of rules.

RULE R1a 
; Half hour setting
IF SIMULATION CLOCKTIME = 0:30:00 
OR SIMULATION CLOCKTIME = 1:30:00  
OR SIMULATION CLOCKTIME = 2:30:00 
OR SIMULATION CLOCKTIME = 3:30:00 
OR SIMULATION CLOCKTIME = 4:30:00 
OR SIMULATION CLOCKTIME = 5:30:00 
OR SIMULATION CLOCKTIME = 6:30:00 
OR SIMULATION CLOCKTIME = 7:30:00 
OR SIMULATION CLOCKTIME = 8:30:00 
OR SIMULATION CLOCKTIME = 9:30:00 
OR SIMULATION CLOCKTIME = 10:30:00
OR SIMULATION CLOCKTIME = 11:30:00
OR SIMULATION CLOCKTIME = 12:30:00 
OR SIMULATION CLOCKTIME = 13:30:00  
OR SIMULATION CLOCKTIME = 14:30:00 
OR SIMULATION CLOCKTIME = 15:30:00 
OR SIMULATION CLOCKTIME = 16:30:00  
OR SIMULATION CLOCKTIME = 17:30:00 
OR SIMULATION CLOCKTIME = 18:30:00 
OR SIMULATION CLOCKTIME = 19:30:00 
OR SIMULATION CLOCKTIME = 20:30:00 
OR SIMULATION CLOCKTIME = 21:30:00 
OR SIMULATION CLOCKTIME = 22:30:00
OR SIMULATION CLOCKTIME = 23:30:00
THEN ORIFICE R1 SETTING = 0.90
AND  ORIFICE R2 SETTING = 0.90
AND  ORIFICE R3 SETTING = 0.90
AND  ORIFICE R4 SETTING = 0.90
AND  ORIFICE R5 SETTING = 0.90
AND  ORIFICE R6 SETTING = 0.90
AND  ORIFICE R7 SETTING = 0.90

RULE R1b
; hour setting
IF SIMULATION CLOCKTIME = 0:00:00
OR SIMULATION CLOCKTIME = 1:00:00
OR SIMULATION CLOCKTIME = 2:00:00
OR SIMULATION CLOCKTIME = 3:00:00
OR SIMULATION CLOCKTIME = 4:00:00
OR SIMULATION CLOCKTIME = 5:00:00
OR SIMULATION CLOCKTIME = 6:00:00
OR SIMULATION CLOCKTIME = 7:00:00
OR SIMULATION CLOCKTIME = 8:00:00
OR SIMULATION CLOCKTIME = 9:00:00
OR SIMULATION CLOCKTIME = 10:00:00
OR SIMULATION CLOCKTIME = 11:00:00
OR SIMULATION CLOCKTIME = 12:00:00 
OR SIMULATION CLOCKTIME = 13:00:00
OR SIMULATION CLOCKTIME = 14:00:00 
OR SIMULATION CLOCKTIME = 15:00:00
OR SIMULATION CLOCKTIME = 16:00:00
OR SIMULATION CLOCKTIME = 17:00:00
OR SIMULATION CLOCKTIME = 18:00:00 
OR SIMULATION CLOCKTIME = 19:00:00 
OR SIMULATION CLOCKTIME = 20:00:00 
OR SIMULATION CLOCKTIME = 21:00:00 
OR SIMULATION CLOCKTIME = 22:00:00 
OR SIMULATION CLOCKTIME = 23:00:00
THEN ORIFICE R1 SETTING = 0.5
AND  ORIFICE R2 SETTING = 0.5
AND  ORIFICE R3 SETTING = 0.5
AND  ORIFICE R4 SETTING = 0.5
AND  ORIFICE R5 SETTING = 0.5
AND  ORIFICE R6 SETTING = 0.5
AND  ORIFICE R7 SETTING = 0.5

Detention Basin Basics in SWMM 5

Subject:  Detention Basin Basics in SWMM 5

What are the basic elements of a detention pond in SWMM 5?  They are common in our backyards and cities and just require a few basic elements to model.  Here is a model in SWMM 5.0.022 that even has a fountain in the real pond – which we not model for now.   The components of the model are:

1.   An inlet to the pond with a simple time series – a subcatchment can be added to it in a more complicated model but for now we will just have a triangular time series,
2.   A pipe to simulate the flow into the pond from the inlet,
3.   A Storage Node to simulate the Pond that consists of a tabular area curve to estimate the depth and area relationship,
4.   A Storage Node to simulate the Outlet Box of the Pond
5.   Two Small Rectangular Orifices to simulate the low flow outflow from the pond at an elevation less than the weir
6.   A large rectangular orifice to simulate the normal inflow to the Box
7.   A rectangular weir to simulate the flow into the box when the pond water surface elevation is above the box
8.   The outlet of the Box is a circular link with a Free outfall as the downstream boundary condition
9.   The flow graph in the image shows the flow into the box starts from the two small orifices, next from the large orifice and finally from the top of the box or the weir.

http://api.ning.com/files/ZtT72Lr8bEOi83U3XrtN9x2vsbK-V--dbjfMZOFEzO4M22pEDeFsuOE5GdQV8Z354OTHNEpjEZwvHPXYyhvbRqPHSxM4DUjv/detetention_pond.INP

Cutoff Divider in the SWMM 5 Kinematic Wave Solution

Subject: Cutoff Divider in the SWMM 5 Kinematic Wave Solution

A divider node in the SWMM 5 Kinematic Wave solution will divide the inflow to a node for two downstream links based on three criteria:

1. Cutoff Divider,
2. Tabular Divider, and
3. Weir Divider

The rule for a Cutoff Divider is that the flow up to the Cutoff Flow will flow down the undiverted link and any flow over the cutoff flow will go down the diverted link. If the total inflow to a node the current flow in the undiverted link then the extra flow will go down the diverted link even though the flow in the undiverted link is not equal to the cutoff flow.

Figure 1.  How the Cutoff Divider Works in SWMM 5

Diversion LInks in SWMM 5 and 5.0.021

Subject:  Diversion Links in SWMM 5 and 5.0.021

Diversion links in SWMM 5 are Pumps (5 types), Orifices (2 types), Weirs (4 types) and Outlets (3 types).
  

Figure 1.  Diversion Links in SWMM 5

Types of Nodes and Links in SWMM 5 - with Emojis

Subject: 📌 Types of Nodes and Links in SWMM 5

Introduction: 🚀 SWMM 5 is a powerful tool used for simulating the hydrology and hydraulics of urban drainage systems. Central to its modeling capabilities are the nodes and links that constitute the drainage network. Let's delve deeper into understanding these critical components.

Nodes in SWMM 5 📍: Nodes are pivotal points or junctions in the drainage system where water collects and gets distributed. They can be categorized as:

1. Junctions 🚇: These are points where multiple links come together. They represent the convergence or divergence of flow paths. In SWMM 5, there's only one type of junction, but it plays a crucial role in defining the flow dynamics.

2. Storages 🛢️: Storages are areas where water is temporarily held before it's released at a controlled rate. In SWMM 5, there are three types of storage:

   • Surface Storage: Represents flat areas like ponds.
   • Tank Storage: Denotes vertical cylindrical tanks.
   • General Storage: A more flexible form that can represent any shape.

3. Dividers 🚧: Dividers distribute incoming flow into multiple paths. While they can be used in the dynamic wave solution of SWMM 5, they only help divide the flow in the kinematic wave solution. There are four types of dividers in SWMM 5, each with its unique characteristics.

4. Outfalls 🌊: Outfalls represent points where water exits the system, either into a larger body of water or another system. SWMM 5 offers five types of outfalls, each designed to simulate different outflow conditions.

Links in SWMM 5 ⛓️: Links are the channels or pathways that connect nodes and facilitate the flow of water between them. They include:

1. Conduits 🚰: These are pipes or channels that transport water between nodes. They can vary in shape, size, and material.

2. Pumps 🔄: Pumps are devices that move water from one node to another, typically from a lower elevation to a higher one.

3. Orifices ⚙️: Orifices control the flow of water between nodes based on the opening size and elevation.

4. Weirs 🌁: Weirs are barriers that redirect or measure flow. They can be sharp-crested, broad-crested, or even compound.

5. Outlets 🚪: Outlets control the discharge of water from a node based on the depth or head of water.

Conclusion 🌟: Understanding nodes and links in SWMM 5 is paramount for effective modeling. These components are the building blocks of the drainage system, and their accurate representation ensures reliable and meaningful simulation results. 📊🛠️

Figure 1.  Node and Link Objects in SWMM 5

Figure 2:  Node Objects in SWMM 5

Time Step Selection in SWMM 5

Subject: Time Step Selection in SWMM 5
1^st The time step you use in SWMM 5 is controlled from the top by the rainfall interval (Figure 1):
1. All of your time steps should be less than the rainfall interval,
2. The hydrology time step should be less than or equal to the smallest raingage rainfall interval in your network,
3. The hydraulic time step should be less than or equal to the hydrology time step and should be based on the hydraulic needs of the your network. Short length links, pump and weirs may require a smaller maximum hydraulic time step.
2^nd The report time step controls what you see in the graphics output of SWMM 5. If you see a large difference between that you see in the graphics output and the report text file it is because you have a large difference between the report time step and the average time step used during the simulation.
Solution: If there is a large discrepancy in the graphics and report text file then the best solution is to reduce the maximum time hydraulic time step so it is closer to the average time step and also to make the report time step closer to the Maximum time step (Figure 2).

Figure 1: Relationship between the rainfall, hydrology and hydraulic time steps.

Figure 2: Relationship between the minimum, average and maximum simulation time steps and the report time step.

PID Control in SWMM 5 for a Weir

Subject: PID Control in SWMM 5 for a Weir

The blog http://swmm5.blogspot.com/2010/12/pid-control-in-swmm-5-for-type-3-pump.html describes theFunction getPIDSetting which returns the PID setting at each time step. The PID parameter set contains three values -- a proportional gain coefficient, an integral time (in minutes), and a derivative time (in minutes) which are kp, ki and kd, respectively. More about the theory of PID controllers can be found at http://en.wikipedia.org/wiki/PID_controller.

Here is an example PID Rule that will keep the node depth at 3 feet in a SWMM 5 model by changing the Weir Setting. The example file is attached in this blog. In this particular example, you can reduce the oscillations about the 3 foot rule level by lowering the integral time and derivative time coefficients in the PID control rule.

RULE PID_Weir
; the PID controller adjusts the weir height to have a
; depth of 3 feet in Node 82309e
IF NODE 82309c DEPTH <> 3
THEN WEIR WEIR1@82309c-15009c SETTING = PID 10 -.01 -.01
; kp ki kd
PRIORITY 1

Manhole Elevations in InfoSWMM and SWMM 5

Subject: Manhole Elevations in InfoSWMM and SWMM 5
Starting from the bottom of the manhole you have these regions of computational interest:
1. Manhole Invert to the lowest link invert – the node continuity equation is used with the area of the manhole being the default surface area of a manhole,
2. Lowest Link Invert to the Highest Link Crown Elevation – the node continuity equation is used with surface of the node being normally half of the surface area of the incoming and outgoing links,
3. Highest Manhole Pipe Crown Elevation to Manhole Rim Elevation – the node surcharge algorithm in which the surface area of the manhole is not used and the surcharge depth is iterated until the inflow and the outflows of the node are in balance,
4. The region above the Manhole Rim Elevation which can use one of four options to calculate the depth and/or flow out of or into the manhole:

1. No Surcharge Depth is entered and No Ponding area is used – the excess water into the manhole is lost to the network and shows up as internal outflow in the continuity tables,

2. A Ponding Area is used and the excess flow will pond on the surface of the manhole and later go back down into the conveyance pipes.

3. A Surcharge Depth is used and the depth will continue to be calculated using the node surcharge algorithm in which the surface area of the manhole is not used and the surcharge depth is iterated until the inflow and the outflows of the node are in balance,

4. A Dual Drainage system is simulated and the excess flow of the manhole is simulated in the street gutters or the actual street,

5. You use a 1D/2D linkage between the 1D manhole and 1D links to a 2D Mesh and simulate the flow out and the flow into the manhole using a bottom outlet orifice that switches automatically between weir and orifice flow based on the depth on top of the manhole.

Weirs in InfoSWMM and SWMM 5

Subject: Weirs in InfoSWMM and SWMM 5
Figure 1 shows the relationship between the weir input data and the upstream and downstream nodes.
· Height,
· Crest and
· Node Invert Elevation
There are four types of weirs and if the weir becomes submerged downstream the Villemonte weir submergence correction is applied (Figure 2). You can have flow reversal across the weir unless you use a Flap Gate for the weir (Figure 3).


Figure 1: Definition of Weir Terms

Figure 2: Villemonte Weir Submergence Correction

Figure 3: Flow Reversal in a Weir

Weirs in InfoSWMM and SWMM5 by dickinsonre Weirs in InfoSWMM and SWMM5 Subject: Weirs in InfoSWMM  Figure 1 shows the relationship between the weir input data and the upstream and  downstream nodes. ·         Height, ·         Crest and ·         Node Invert Elevation  There are four types of weirs and if the weir becomes submerged downstream the Villemonte weir submergence correction is applied (Figure 2).  You can have flow reversal across the weir unless you use a Flap Gate for the weir (Figure 3).

Figure 1:  Definition of Weir Terms

Figure 2: Villemonte Weir Submergence Correction

Figure 3:  Flow Reversal in a Weir

via Blogger http://www.swmm5.net/2013/07/weirs-in-infoswmm-and-swmm5.html