The Urban Conduit Link
- 23 Oct 2022
- 4 Minutes to read
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The Urban Conduit Link
- Updated on 23 Oct 2022
- 4 Minutes to read
- Print
- DarkLight
Article Summary
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Conduit links represent the pipes themselves connecting the nodes in your urban system.
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Rules of Conduit links
If using Steady or Kinematic Wave routing, only a single outflow Conduit link is allowed from an Urban Junction Node. Multiple Conduit links can be conected to a Junction node if using Dynamic Wave routing.
Exactly two outflow Conduit links must be connected from an Urban Divider Node.
Only one (inflow) Conduit link can be connected to an Urban Outfall Node.
If using Kinematic Wave routing, Conduit links are the only link type allowed, aside from the outflow link from an Urban Storage Node.
Conduit label/name
The Conduit node name by default will be provided by parameters setup in the Urban Model Defaults menu.
Optional descriptors
Description
This field allows for an optional text description. The field will be blank by default.
Tag
This field allows for an optional text tag, to allow you to categorise units. The field will be blank by default.
Shape/Depth
Fields are provided for the Shape and Max. Depth of the Conduit. By default, these are based on values set on the Model Defaults window.
The 3 dots to the right of the Shape field enable access to the Cross-Section Editor window, from which a conduit shape, maximum depth, and number of barrels (identical, parallel pipes) can be specified. The maximum depth specified here will automatically populate the Max. Depth field in the conduit properties window.
Length
The conduit Length is required. This will be set by default to the value set in the Model Defaults window.
The Length will be automatically calculated from the length of the line drawn on the map if the default length is set to zero in the Model Defaults window. This length is only calculated at the point of the link being drawn (already drawn links must be deleted and re-drawn for the length to be calculated from the map).
Roughness
The conduit Roughness is required. This will be set by default to the value set in the Model Defaults window.
Additional Parameters
Inlet Offset
Conduit links can have an offset specified at the inflow and outflow ends. This is the distance from the invert level of the inflow node. The value may be as a depth or elevations, as specified by the Offset convention set in the Model Defaults window.
Outlet Offset
Conduit links can have an offset specified at the inflow and outflow ends. This is the distance from the invert level of the outflow node. The value may be as a depth or elevations, as specified by the Offset convention set in the Model Defaults window.
Maximum Flow
The Conduit maximum flow. This can be left blank if not applicable.
Entry Loss Coeff.
This field specifies the head loss coefficient associated with energy losses at the entrance of the conduit. We refer the user to the EPA Manual for further details.
Exit Loss Coeff.
This field specifies the head loss coefficient associated with energy losses at the exit of the conduit. We refer the user to the EPA Manual for further details.
Avg. Loss Coeff.
This field specifies the head loss coefficient associated with energy losses along the length of the conduit.
Flap Gate
A Flap Gate can be specified so prevent backflow. This option will be set to NO by default.
Culvert Code
If a Culvert Inlet Geometry code number is assigned to a conduit, it will act as a culvert. This should be used only for conduits that act as culverts and should be analysed for inlet control conditions using the FHWA HDS-5 method. These code numbers are listed in below.
| Type | Description | Code |
|---|---|---|
| Circular Concrete | Square edge with headwall Groove end with headwall Groove end projecting | 1 2 3 |
| Circular Corrugated Metal Pipe | Headwall Mitered to slope Projecting | 4 5 6 |
| Circular Pipe, Beveled Ring Entrance | 45 deg. bevels 33.7 deg. bevels | 7 8 |
| Rectangular Box; Flared Wingwalls | 30-75 deg. wingwall flares 90 or 15 deg. wingwall flares 0 deg. wingwall flares (straight sides) | 9 10 11 |
| Rectangular Box;Flared Wingwalls and Top Edge Bevel: | 45 deg flare; 0.43D top edge bevel 18-33.7 deg. flare; 0.083D top edge bevel | 12 13 |
| Rectangular Box, 90-deg Headwall, Chamfered / Beveled Inlet Edges | chamfered 3/4-in. beveled 1/2-in/ft at 45 deg (1:1) beveled 1-in/ft at 33.7 deg (1:1.5) | 14 15 16 |
| Rectangular Box, Skewed Headwall, Chamfered / Beveled Inlet Edges | 3/4" chamfered edge, 45 deg skewed headwall 3/4" chamfered edge, 30 deg skewed headwall 3/4" chamfered edge, 15 deg skewed headwall 45 deg beveled edge, 10-45 deg skewed headwall | 17 18 19 20 |
| Rectangular Box, Non-offset Flared Wingwalls, 3/4" Chamfer at Top of Inlet | 45 deg (1:1) wingwall flare 8.4 deg (3:1) wingwall flare 18.4 deg (3:1) wingwall flare, 30 deg inlet skew | 21 22 23 |
| Rectangular Box, Offset Flared Wingwalls, Beveled Edge at Inlet Top | 45 deg (1:1) flare, 0.042D top edge bevel 33.7 deg (1.5:1) flare, 0.083D top edge bevel 18.4 deg (3:1) flare, 0.083D top edge bevel | 24 25 26 |
| Corrugated Metal Box | 90 deg headwall Thick wall projecting Thin wall projecting | 27 28 29 |
| Horizontal Ellipse Concrete | Square edge with headwall Grooved end with headwall Grooved end projecting | 30 31 32 |
| Vertical Ellipse Concrete | Square edge with headwall Grooved end with headwall Grooved end projecting | 33 34 35 |
| Pipe Arch, 18" Corner Radius, Corrugated Metal | 90 deg headwall Mitered to slope Projecting | 36 37 38 |
| Pipe Arch, 18" Corner Radius, Corrugated Metal | Projecting No bevels 33.7 deg bevels | 39 40 41 |
| Pipe Arch, 31" Corner Radius,Corrugated Metal | Projecting No bevels 33.7 deg. bevels | 42 43 44 |
| Arch, Corrugated Metal | 90 deg headwall Mitered to slope Thin wall Projecting | 45 46 47 |
| Circular Culvert | Smooth tapered inlet throat Rough tapered inlet throat | 48 49 |
| Elliptical Inlet Face | Tapered inlet, beveled edges Tapered inlet, square edges Tapered inlet, thin edge projecting | 50 51 52 |
| Rectangular | Tapered inlet throat | 53 |
| Rectangular Concrete | Side tapered, less favorable edges Side tapered, more favorable edges Slope tapered, less favorable edges Slope tapered, more favorable edges | 54 55 56 57 |
We refer the user to the EPA Manual for further details, where the following is stated.
Culvert conduits are checked continuously during dynamic wave flow routing to see if they operate under Inlet Control as defined in the Federal Highway Administration’s publication Hydraulic Design of Highway Culverts Third Edition (Publication No. FHWA-HIF-12-026, April 2012). Under inlet control a culvert obeys a particular flow versus inlet depth rating curve whose shape depends on the culvert’s shape, size, slope, and inlet geometry.
Equations
The 1D urban solver uses the Manning equation to express the relationship between cross-sectional area, hydraulic radius, slope and flow rate in all conduits. We refer the user to the EPA Manual for further details.
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