Difference between revisions of "1D Manholes"

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<font size = 18>Page Under Construction</font>
 
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=Introduction=
 
=Introduction=
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Manholes are typically chambers used to provide one or all of the following; maintenance access, change in culvert direction, connections and change in culvert dimensions. By default, manholes are automatically created within TUFLOW at all culvert nodes, any manually created manhole will override the automatically created manhole.  
+
Manholes are typically chambers used to provide one or all of the following; maintenance access, change in culvert direction, connections and change in culvert dimensions. By default, manholes are automatically created within TUFLOW at all conduit nodes, any manually created manhole will override the automatically created manhole.
  
−
Manholes are used at culvert junctions to dissipate energy due to: <br>
+
Manholes are used at conduit junctions to dissipate energy due to: <br>
−
*Expansion/contraction of flow within the manhole chamber and outlet culverts.
+
*Expansion/contraction of flow within the manhole chamber and outlet conduits.
−
*Change in direction of the culverts (i.e. a bend/deflection).
+
*Change in direction of the conduits (i.e. a bend/deflection).
−
*Change in height, width or diameter and/or invert level of the adjoining culverts.  
+
*Change in height, width or diameter and/or invert level of the adjoining conduits.  
 
<br>
 
<br>
−
The presence of a manhole at a junction point will override the exit loss of any culvert discharging into the manhole and entrance loss of any culvert taking from our of the manhole. <br>
+
The presence of a manhole at a junction point will override the exit loss of any conduit discharging into the manhole and entrance loss of any conduit coming out of the manhole. <br>
 
<br>
 
<br>
−
There are 3 types of manholes:
+
There are 3 types of manholes which can be specified in the 1d_mh_* layer:
 
*"C" for circular chambers.
 
*"C" for circular chambers.
 
*"R" for rectangular chambers.
 
*"R" for rectangular chambers.
−
*"J" for junctions without a chamber
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*"J" for junctions without a chamber.
 
<br>
 
<br>
  
−
=Losses=
+
=Manhole Losses=
−
When modelling conduit pipe flows, the head losses that the flow in pipe are subject to are made up of major losses (or friction losses) and minor losses (or local losses).  Major losses are caused by forces between the flow and wetted perimeter of the conduit.  Minor losses are caused by disruption to the flow due to bends, cross-sectional changes, fittings such as manholes and steps in the bed profile.  Major losses are represented through the specification of a friction coefficient.  The representation of minor losses, particularly or gravity networks, is at manholes and requires separate treatment.  The default TUFLOW/Estry manhole loss approach uses the Engelund method explained in section 5.12.5.4 of the TUFLOW user manual.  The Engelund approach provides an automatic method for determining the loss coefficients as presented below.  Of note is that the coefficients are recalculated every timestep, and therefore vary depending on the flow distribution between inlet and outlet conduits and the depth of water within the manhole.  The losses represented are as follows:
+
When modelling conduit pipe flows, the head losses that the flow in pipe are subject to are made up of major losses (or friction losses) and minor losses (or local losses).  Major losses are caused by forces between the flow and wetted perimeter of the conduit.  Minor losses are caused by disruption to the flow due to bends, cross-sectional changes, fittings such as manholes and steps in the bed profile.  Major losses are represented through the specification of a friction coefficient.  The representation of minor losses, particularly for gravity networks, is at manholes and requires separate treatment.  The default TUFLOW/Estry manhole loss approach uses the Engelund method explained in section 5.12.5.4 of the [https://downloads.tuflow.com/_archive/TUFLOW/Releases/2018-03/TUFLOW%20Manual.2018-03.pdf TUFLOW user manual] although it is also possible to use a more simplified fixed manhole headloss approach too using the global <font color="blue"><tt>Manhole Default Loss Approach</tt></font> command or specifying within the '1d_mH_*' layer in the Loss_Approach attribute.  The Engelund approach provides an automatic method for determining the loss coefficients as presented below.  Of note is that the coefficients are recalculated every timestep, and therefore vary depending on the flow distribution between inlet and outlet conduits and the depth of water within the manhole.  The losses represented are as follows:
−
 
+
<br>
 
<li>'''K<sub>entry</sub>''' covers the expansion of flow within the manhole at the outlet of an inlet conduit.  The coefficient is applied as the exit loss of the inlet conduit.   
 
<li>'''K<sub>entry</sub>''' covers the expansion of flow within the manhole at the outlet of an inlet conduit.  The coefficient is applied as the exit loss of the inlet conduit.   
−
<li>'''K<sub>Ɵ</sub>''' represents the losses due to a change in direction (i.e. a bend) between inlet and outlet conduits.  KƟ is determined automatically by TUFLOW based on the angle of the digitised lines of the conduits.  For the inlet conduit the last two vertices of the line are used and for the outlet conduit the first two vertices.   
+
<li>'''K<sub>Ɵ</sub>''' represents the losses due to a change in direction (i.e. a bend) between inlet and outlet conduits.  K<sub>Ɵ</sub> is determined automatically by TUFLOW based on the angle of the digitised lines of the conduits.  For the inlet conduit the last two vertices of the line are used and for the outlet conduit the first two vertices.   
 
<li>'''K<sub>drop</sub>''' is the loss coefficient due to a change in invert level and conduit height between inlet and outlet conduits.
 
<li>'''K<sub>drop</sub>''' is the loss coefficient due to a change in invert level and conduit height between inlet and outlet conduits.
 
<li>'''K<sub>Ɵ</sub>''' and '''K<sub>drop</sub>''' are added and applied as an energy loss for each outlet conduit.   
 
<li>'''K<sub>Ɵ</sub>''' and '''K<sub>drop</sub>''' are added and applied as an energy loss for each outlet conduit.   
−
<li>'''K<sub>exit</sub>''' covers the contraction from the manhole and re-expansion of flow within the entrance of an outlet conduit.  It is applied as an entrance loss of the outlet.
+
<li>'''K<sub>exit</sub>''' covers the contraction from the manhole and re-expansion of flow within the entrance of an outlet conduit.  It is applied as an entrance loss of the outlet.<br>
−
<li>'''K<sub>m</sub>''' is the user-defined manhole exit coefficient.   
+
<li>'''K<sub>m</sub>''' is the user-defined manhole exit coefficient.  <br>
−
 
+
<br>
−
The resulting headloss value is then applied, when sub-critical flow is experienced, to the standard head loss equation, i.e. dh = K*V<sup>2</sup>/2g.  Where K is the loss coefficient, V is the conduit velocity and g the gravitational constant.  The equations used for the Engelund loss approach are provided below:
+
The resulting headloss value is then applied, when sub-critical flow is experienced, to the standard head loss equation, i.e. dh = K*V<sup>2</sup>/2g.  Where K is the loss coefficient, V is the conduit velocity and g the gravitational constant.  The equations used for the Engelund loss approach are provided below:<br>
 
<br>
 
<br>
−
[[File:Engelund Equations.PNG]]
+
[[File:Engelund Equations.PNG|500px]]
 
<br>
 
<br>
  
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'''W<sub>m</sub>''' = Flow width in manhole (1d_mh width attribute) <br>
 
'''W<sub>m</sub>''' = Flow width in manhole (1d_mh width attribute) <br>
 
'''y<sub>m</sub>''' = Depth of water in manhole <br>
 
'''y<sub>m</sub>''' = Depth of water in manhole <br>
−
'''A<sub>m</sub>''' = Flow are in manhole <br>
+
'''A<sub>m</sub>''' = Flow area in manhole <br>
−
'''A'<sub>m</sub>''' = Effective flow are in manhole <br>
+
'''A'<sub>m</sub>''' = Effective flow area in manhole <br>
 
'''A<sub>p</sub>''' = Flow area of conduit <br>
 
'''A<sub>p</sub>''' = Flow area of conduit <br>
 
'''K<sub>m</sub>''' = Manhole Loss Parameter (1d_mh Km attribute) <br>
 
'''K<sub>m</sub>''' = Manhole Loss Parameter (1d_mh Km attribute) <br>
Line 55: Line 50:
 
'''K<sub>Bendmax</sub>''' = Upper limit to sum of K<sub>θ</sub> and K<sub>drop</sub> (1d_mh K_Bend_Max attribute) <br>
 
'''K<sub>Bendmax</sub>''' = Upper limit to sum of K<sub>θ</sub> and K<sub>drop</sub> (1d_mh K_Bend_Max attribute) <br>
 
<br>
 
<br>
−
Below are three worked examples of the application of the Engelund method applied to a simple model for the following scenarios:
+
There are three worked examples of the application of the Engelund method applied to a simple model for the following scenarios at the following pages:
−
       <li>Single Incoming/Outgoing Pipe with no angle and no drop
+
       <li>[[Manhole_Simple_Loss_Example#Example 1: Single Incoming/Outgoing Pipe with No Incoming Angle or Drop|Single Incoming/Outgoing Pipe with no angle and no drop]]
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       <li>Single Incoming/Outgoing Pipe with incoming bend and drop in levels
+
       <li>[[Manhole_Simple_Loss_Example#Example 2: Single Incoming/Outgoing Conduit with Incoming Bend and Drop in Invert Levels|Single Incoming/Outgoing Pipe with incoming bend and drop in levels]]
−
       <li>Multiple Incoming Pipes with incoming bend and drop in levels
+
       <li>[[Manhole_Simple_Loss_Example#Example 3: Multiple Incoming Conduits with Incoming Bend and Drop in Invert Levels|Multiple Incoming Pipes with incoming bend and drop in levels]]<br>
−
==Example 1: Single Incoming/Outgoing Pipe with No Incoming Angle or Drop==
 
−
<br>
 
−
A simple TUFLOW/ESTRY model was set up as shown in Figure 1 with the parameters for the manhole and the links upstream/downstream of the manhole shown in Table 1.
 
−
<br>
 
−
[[File:Schematic 1.png]]
 
−
<br>
 
−
'''Figure 1: Example Model 1 Network Schematic'''
 
−
<br>
 
−
[[File:Long Profile 1.png]]
 
−
<br>
 
−
'''Figure 2: Example Model 1 Long Section'''
 
−
<br>
 
−
{| align="center" class="wikitable"
 
  
−
! style="background-color:#005581; font-weight:bold; color:white;"| Parameter
 
−
! style="background-color:#005581; font-weight:bold; color:white;"| Upstream Conduit
 
−
!style="background-color:#005581; font-weight:bold; color:white;"| Downstream Conduit
 
−
! style="background-color:#005581; font-weight:bold; color:white;" width=25% | Manhole
 
−
|-
 
−
|ID || UC-2 || Manhole || DC-1
 
−
|-
 
−
|Type || R || R || R
 
−
|-
 
−
|Invert Level (m AD) || N/A || N/A || 99.6
 
−
|-
 
−
|Upstream Invert Level (m AD) || 99.8 ||99.7 || N/A
 
−
|-
 
−
|Downstream Invert Level (m AD) || 99.7 || 99.6 || N/A
 
−
|-
 
−
|Width(m) || 1 || N/A || 1
 
−
|-
 
−
|Form Loss || 0 || 1 || N/A
 
−
|-
 
−
|Flow Width(m) || N/A || N/A || 1.8
 
−
|-
 
−
|K_Fixed || N/A || N/A || 2
 
−
|-
 
−
|Km || N/A || N/A || 1
 
−
|}
 
−
'''Table 1: Relevant Model Parameters for Hand Calculations'''
 
−
<br>
 
−
The model was run with a steady inflow of 2m<sup>3</sup>s<sup>-1</sup>.  The resulting losses from the 1 hour steady inflow simulation are presented in the following figure.
 
−
<br>
 
−
[[File:Manhole Results 1.png]]
 
 
<br>
 
<br>
−
'''Figure 3: Example Model 1 Results-Loss Coefficients'''
+
In the case of the fixed headloss approach, the 1d_mh_* K_Fixed attribute is applied to the standard head loss equation, i.e. dh = K*V<sup>2</sup>/2g on the outlet conduit(s).<br>
 
<br>
 
<br>
  
−
===Example 1 - Entry Losses===
+
=Manhole Storage=
−
Entry losses are applied as an exit loss on the incoming conduit and are calculated as follows.
+
Storage, including shaft storage, storage chambers or floodplain storage, can be manually defined using a 1d_na (1d_tab_empty) node that has an assigned elevation versus surface area table. For the purpose of this page, manmade storage chambers have been discussed although the method is the same for all applications. <br>
−
[[File:K entry.PNG]]
 
−
<br>
 
−
Where:
 
−
[[File:Vp.PNG]]
 
−
<br>
 
−
With other parameters defined in the section above.  The calculated flow area in the manhole is 3.6m<sup>2</sup> and 1m<sup>2</sup> in the adjacent culvert whilst the flow is 2m<sup>3</sup>/s for both Q<sub>p</sub> and Q<sub>om</sub>. 
 
−
Therefore, V<sub>m</sub> equals:
 
−
[[File:Vm1.PNG]]
 
−
<br>
 
−
And V<sub>p</sub>:
 
−
[[File:VP1.PNG]]
 
−
<br>
 
−
Using these in the K<sub>entry</sub> equation provides a loss coefficient of:
 
−
[[File:K entry1.PNG]]
 
−
<br>
 
−
The value matches the downstream loss coefficient for the upstream conduit shown in Figure X.  The loss values are also shown in the *_TSL_P.shp file with the third value for the upstream conduit providing the entrance loss value.
 
−
 
 
−
===Example 1 - Exit Losses===
 
−
Exit losses are applied to the upstream end of the outgoing conduit and are calculated as follows: [[File:K exit.PNG]]
 
−
<br>
 
−
From table 1, we can see that K<sub>m</sub> is  set to 1. A<sub>p</sub> and A’<sub>m</sub> are 1m<sup>2</sup> and 3.636m<sup>2</sup> respectively.  Therefore, K<sub>exit</sub> is: [[File:K exit1.PNG]]
 
−
 
 
−
Figure 3 shows that the calculated value matches those provided in the TUFLOW results.  The value is also reported as the first value for the downstream conduit in the *_TSL_P.shp layer.
 
−
 
 
−
===Example 1 - Outgoing Conduit Losses===
 
−
 
 
−
The loss coefficient for the outgoing pipe represents the losses due to the incoming angle of the upstream conduit, any drops in inverts levels between the incoming and outgoing conduits, bend losses and any additional form losses.  It is calculated as follows:
 
−
 
 
−
[[File:K outletpipe.PNG]]
 
−
 
 
−
The default value of K<sub>Bend_max</sub> is set to 4 but can be changed via the 1d_mh K_Bend_Max attribute.  As shown above we have no angle for the incoming pipe and no drop in invert levels.  Table 1 shows the K_Fixed is equal to 2 and the outgoing pipe has a form loss coefficient, to represent bend losses of 1.  Therefore K<sub>outletpipe</sub> is:
 
−
[[File:K outletpipe1.PNG]]
 
−
 
 
−
This matches the value within Figure 3 and the middle value for the downstream conduit in the *_TSL_P.shp, representing the outlet conduit losses, of 3.
 
−
 
 
−
==Example 2: Single Incoming/Outgoing Conduit with Incoming Bend and Drop in Invert Levels==
 
−
 
 
−
In this example, we will use the same simple setup but this time there is a 90 degree angle between the incoming and outgoing pipe as shown in the plan view in the figure below.
 
−
<br>
 
−
[[File:Schematic 2.png]]
 
−
<br>
 
−
'''Figure 4: Example Model 2 Network Schematic'''
 
−
 
 
−
There is also a drop between the invert elevation of the incoming and outgoing conduits as shown in the difference in invert levels in table 2 below and the long profile in figure 5 .  All other model parameters were kept the same including boundary inflows.
 
−
<br>
 
−
[[File:Long Profile 2.png]]
 
−
<br>
 
−
'''Figure 5: Example Model 2 Long Profile'''
 
−
 
 
−
The resulting simulated losses are shown in the below figure 6.
 
−
<br>
 
−
[[File:Manhole Results 2.png]]
 
−
<br>
 
−
'''Figure 6: Example Model 2 Results-Loss Coefficients'''
 
−
<br>
 
−
===Example 2 - Entry Losses===
 
−
 
 
−
In this example, the flow area in the manhole is 4.12m<sup>2</sup> and 1m<sup>2</sup> in the adjacent culvert whilst the flow is 2m<sup>3</sup>/s for both Q<sub>p</sub> and Q<sub>om</sub>. 
 
−
Therefore, Vm equals:
 
−
[[File:Vm2.PNG]]
 
−
<br>
 
−
And V<sub>p</sub>:
 
−
[[File:Vp2.PNG]]
 
−
<br>
 
−
From this:
 
−
[[File:K entry2.PNG]]
 
−
 
 
−
Which matches the value in figure 6.
 
−
 
 
−
===Example 2 - Exit Losses===
 
−
 
 
−
In this example, A'<sub>m</sub> is 4.12m<sup>2</sup>, therefore K<sub>exit</sub>:[[File:K exit2.PNG]]
 
−
 
 
−
Which matches the result in figure 6.
 
−
 
 
−
===Example 2 - Outgoing Conduit Losses===
 
−
On this occasion, we have an 90 degree angle between the incoming and outgoing conduit.  Therefore, we need to calculate Kθ using the following equation: [[File:Ktheta.PNG]]
 
−
<br>
 
−
Q<sub>f</sub> is calculated as: [[File:Qf.PNG]]
 
−
<br>
 
−
Q<sub>p</sub> and Q<sub>om</sub> are both 2m<sup>3</sup>s<sup>-1</sup> and therefore Q<sub>f</sub> is equal to 1.  The incoming conduit angle is 90 degrees which is cancelled out by the denominator.  K<sub>θ</sub> is therefore:[[File:Ktheta1.PNG]]
 
−
 
 
−
We also have a drop between the incoming and outgoing pipes.  K<sub>drop</sub> which represents losses due to this drop is calculated as follows:[[File:Kdrop.PNG]]
 
−
 
 
−
Which is:[[File:Kdrop 1.PNG]]
 
−
 
 
−
Therefore K<sub>outletpipe</sub> is:[[File:K outletpipe2.PNG]]
 
−
 
 
−
This matches the simulated value in figure 6.
 
−
 
 
−
==Example 3: Multiple Incoming Conduits with Incoming Bend and Drop in Invert Levels==
 
−
 
 
−
In this example we have multiple incoming conduit.  Each upstream conduit has a flow of 1m<sup>3</sup>s<sup>-1</sup> applied to it.
 
−
 
 
−
[[File:Schematic 3.png]]
 
−
<br>
 
−
'''Figure 7: Example Model 3 Network Schematic'''
 
−
<br>
 
−
The conduits are the same shape and the same dimensions but have different invert levels as specified in the table below.  All parameters for the manhole and other parts of the network are identical.
 
−
 
 
−
The resulting simulated loss values are presented in Figure 8.
 
−
<br>
 
−
[[File:Manhole Results 3.png]]
 
−
<br>
 
−
'''Figure 8: Example Model 3 Results-loss Coefficients'''
 
−
<br>
 
−
===Example 3 - Entry Losses===
 
−
 
 
−
This time the flow area in the manhole is 3.57m<sup>2</sup> and 1m<sup>2</sup> in the adjacent culvert whilst the flow is 1m<sup>3</sup>/s for Q<sub>p</sub> and 2m<sup>3</sup>s<sup>-1</sup> for Q<sub>om</sub>.  Therefore, V<sub>m</sub> equals:[[File:Vm3.PNG]]
 
−
<br>
 
−
And V<sub>p</sub>:[[File:Vp3.PNG]]
 
−
<br>
 
−
From this:
 
−
[[File:K entry3.PNG]]
 
−
 
 
−
This matches the losses for both incoming pipes as shown in figure 8.
 
−
 
 
−
===Example 3 - Exit Losses===
 
−
A'<sub>m</sub> is 3.57m<sup>2</sup> respectively.  Therefore, K<sup>exit</sup>:[[File:K exit3.PNG]]
 
−
 
 
−
The calculated losses match the losses calculated by the TUFLOW presented in Figure 8.
 
−
 
 
−
===Example 3 - Outgoing Conduit Losses===
 
−
In this model we have two incoming pipes, one with an 90 degree angle between the incoming and outgoing conduit and one with zero.
 
−
Recall that: [[File:Ktheta.PNG]]
 
−
 
 
−
With Qf calculated as: [[File:Qf.PNG]]
 
−
<br>
 
−
Q<sub>p</sub> is set to 1m<sup>3</sup>s<sup>-1</sup> and Q<sub>om</sub> to 2m<sup>3</sup>s<sup>-1</sup>. Q<sub>f</sub> is equal to 0.5m<sup>3</sup>s<sup>-1</sup>.  For the incoming conduit with an angle of 90 degrees,  K<sub>θ</sub> is therefore: [[File:Ktheta2a.PNG]]
 
−
 
 
−
For the incoming conduit with an angle of 0 degrees,  K<sub>θ</sub> is therefore: [[File:Ktheta2b.PNG]]
 
−
 
 
−
We also have a drop between the incoming and outgoing pipes.  K<sub>drop</sub> which represents losses due to this drop is calculated as follows: [[File:Kdrop 2a.PNG]]
 
−
<br>
 
−
and:[[File:Kdrop 2b.PNG]]
 
−
 
 
−
Therefore, K<sub>outletpipe</sub> is: [[File:K outletpipe3.PNG]]
 
−
 
 
−
The calculated value matches that presented in figure 8 for the downstream conduit loss.
 
−
 
 
−
=Storage chambers=
 
−
Storage, including storage chambers or floodplain storage, can be manually defined using a 1d_na (1d_tab_empty) node that has an assigned elevation versus surface area table. For the purpose of this page, manmade storage chambers have been discussed although the method is the same for all applications. <br>
 
 
<br>
 
<br>
 
'''An example of a chamber:'''<br>
 
'''An example of a chamber:'''<br>
Line 256: Line 66:
 
<br>
 
<br>
 
'''Methodology'''<br>
 
'''Methodology'''<br>
−
*Import 1d_na node.
+
*Import the 1d_na node layer.
−
*Assign the name of the elevation vs area csv.
+
*Assign the name of the elevation vs area csv file.
−
*Specify the names for the elevation and surface area columns
+
*Specify the names for the elevation and surface area columns held within the csv file.
 
<br>
 
<br>
 
[[File:Storage_chamber_MI.JPG|border|600px]]
 
[[File:Storage_chamber_MI.JPG|border|600px]]
Line 266: Line 76:
 
[[File:Storage_chamber_csv.JPG|border|400px]]
 
[[File:Storage_chamber_csv.JPG|border|400px]]
 
<br>
 
<br>
−
<br>
+
For more information on storage nodes see Section 5.11.4 ''Storage Nodes (User Defined NA Tables)'' within the [https://downloads.tuflow.com/TUFLOW/Releases/Latest/TUFLOW%20Manual.pdf| TUFLOW user manual]. If you have any further questions about manholes or any other aspect of TUFLOW functionality, please email TUFLOW support: [mailto:support@tuflow.com?Subject=TUFLOW%201D%20manholes%20help support@tuflow.com]
−
For more information on storage nodes see Section 5.10.3 ''Storage Nodes (User Defined NA Tables)'' within the TUFLOW manual.<br>
 
−
<br>
 
−
<br>
 
−
Any further questions please email TUFLOW support: [mailto:support@tuflow.com?Subject=TUFLOW%201D%20manholes%20help support@tuflow.com]
 
 
<br><br>
 
<br><br>
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Back to [[TUFLOW_1D_Hydraulic_Structures | 1D Hydraulic Structures]]
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{{Tips Navigation
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|uplink=[[ TUFLOW 1D Channels and Hydraulic Structures | Back to 1D Channels and Hydraulic Structures]]
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Latest revision as of 16:45, 1 March 2024

Introduction

Manholes are typically chambers used to provide one or all of the following; maintenance access, change in culvert direction, connections and change in culvert dimensions. By default, manholes are automatically created within TUFLOW at all conduit nodes, any manually created manhole will override the automatically created manhole.

Manholes are used at conduit junctions to dissipate energy due to:

  • Expansion/contraction of flow within the manhole chamber and outlet conduits.
  • Change in direction of the conduits (i.e. a bend/deflection).
  • Change in height, width or diameter and/or invert level of the adjoining conduits.


The presence of a manhole at a junction point will override the exit loss of any conduit discharging into the manhole and entrance loss of any conduit coming out of the manhole.

There are 3 types of manholes which can be specified in the 1d_mh_* layer:

  • "C" for circular chambers.
  • "R" for rectangular chambers.
  • "J" for junctions without a chamber.


Manhole Losses

When modelling conduit pipe flows, the head losses that the flow in pipe are subject to are made up of major losses (or friction losses) and minor losses (or local losses). Major losses are caused by forces between the flow and wetted perimeter of the conduit. Minor losses are caused by disruption to the flow due to bends, cross-sectional changes, fittings such as manholes and steps in the bed profile. Major losses are represented through the specification of a friction coefficient. The representation of minor losses, particularly for gravity networks, is at manholes and requires separate treatment. The default TUFLOW/Estry manhole loss approach uses the Engelund method explained in section 5.12.5.4 of the TUFLOW user manual although it is also possible to use a more simplified fixed manhole headloss approach too using the global Manhole Default Loss Approach command or specifying within the '1d_mH_*' layer in the Loss_Approach attribute. The Engelund approach provides an automatic method for determining the loss coefficients as presented below. Of note is that the coefficients are recalculated every timestep, and therefore vary depending on the flow distribution between inlet and outlet conduits and the depth of water within the manhole. The losses represented are as follows:

  • Kentry covers the expansion of flow within the manhole at the outlet of an inlet conduit. The coefficient is applied as the exit loss of the inlet conduit.
  • KƟ represents the losses due to a change in direction (i.e. a bend) between inlet and outlet conduits. KƟ is determined automatically by TUFLOW based on the angle of the digitised lines of the conduits. For the inlet conduit the last two vertices of the line are used and for the outlet conduit the first two vertices.
  • Kdrop is the loss coefficient due to a change in invert level and conduit height between inlet and outlet conduits.
  • KƟ and Kdrop are added and applied as an energy loss for each outlet conduit.
  • Kexit covers the contraction from the manhole and re-expansion of flow within the entrance of an outlet conduit. It is applied as an entrance loss of the outlet.
  • Km is the user-defined manhole exit coefficient.

    The resulting headloss value is then applied, when sub-critical flow is experienced, to the standard head loss equation, i.e. dh = K*V2/2g. Where K is the loss coefficient, V is the conduit velocity and g the gravitational constant. The equations used for the Engelund loss approach are provided below:

    Engelund Equations.PNG
    Where:
    Qp = Flow in Conduit
    Qim = Total flow into manhole
    Qom = Total flow out of manhole
    yi = Height of inlet conduit
    yo = Height of outlet conduit
    hi = Inlet conduit invert
    ho = Outlet Conduit invert
    θ = Angle in degrees of inlet conduit relative to outlet conduit(θ = 0° "when the culverts are in line," θ=90° when the outlet culvert is at right angles)
    Qp = Flow in conduit outlet
    Wm = Flow width in manhole (1d_mh width attribute)
    ym = Depth of water in manhole
    Am = Flow area in manhole
    A'm = Effective flow area in manhole
    Ap = Flow area of conduit
    Km = Manhole Loss Parameter (1d_mh Km attribute)
    Kb = Bend Loss Coefficient (1d_nwk Form_loss attribute)
    Kf = Fixed Loss (1d_mh K_Fixed attribute)
    KBendmax = Upper limit to sum of Kθ and Kdrop (1d_mh K_Bend_Max attribute)

    There are three worked examples of the application of the Engelund method applied to a simple model for the following scenarios at the following pages:
  • Single Incoming/Outgoing Pipe with no angle and no drop
  • Single Incoming/Outgoing Pipe with incoming bend and drop in levels
  • Multiple Incoming Pipes with incoming bend and drop in levels

    In the case of the fixed headloss approach, the 1d_mh_* K_Fixed attribute is applied to the standard head loss equation, i.e. dh = K*V2/2g on the outlet conduit(s).

    Manhole Storage

    Storage, including shaft storage, storage chambers or floodplain storage, can be manually defined using a 1d_na (1d_tab_empty) node that has an assigned elevation versus surface area table. For the purpose of this page, manmade storage chambers have been discussed although the method is the same for all applications.

    An example of a chamber:

    www.humes.com.au


    Methodology

    • Import the 1d_na node layer.
    • Assign the name of the elevation vs area csv file.
    • Specify the names for the elevation and surface area columns held within the csv file.


    Storage chamber MI.JPG
    storage_chamber.csv
    Storage chamber csv.JPG
    For more information on storage nodes see Section 5.11.4 Storage Nodes (User Defined NA Tables) within the TUFLOW user manual. If you have any further questions about manholes or any other aspect of TUFLOW functionality, please email TUFLOW support: support@tuflow.com

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