Outlets

Outlets are flow control structures typically used to control outflows from storage units. They are used to model special flow-head relations that cannot be characterized by either orifices or weirs. MIKE+ SWMM represents an Outlet as a link connecting two nodes, where the outlet itself is placed at the upstream node.

Outlets attached to storage units are active under all types of flow routing. Those attached to other types of nodes are active only under Dynamic Wave flow routing; otherwise the flow through them is zero.

The Outlet editor organizes the related input data into the following groups:

• Identification. General identification and connectivity information
• Hydraulic Properties. Hydraulic and geometric parameters for the outlet
• Description. Optional descriptive information about the element. Also includes an option for adding images of the structure.

 

Figure: The SWMM Outlets editor

Identification

The identification group box holds element ID and connectivity information. Use the Insert or Delete buttons to add or remove records from the editor, respectively.

 

Figure: Outlets Identification groupbox

Edit field	Description	Used or required by simulations	Field name in datastructure
ID	Id of the Outlet	Yes	MUID
Location	Node location of the outlet	Yes	FromNodeID
To	Receiving node	No	ToNodeID
Description
Description	Descriptive information for the outlet	No	Description
Data Source	Reference to an external data source from which the record was imported	No	DataSource
Asset ID	Id in the asset database	No	AssetName
Status	Status according to user specified list in Status Codes editor	No	Element_S
Network Type	Network type describes the type of network i.e Stormwater, Combined or separate. The list of network types can be extended by user. Network type can be specified for each hydraulic element.	No	NetTypeNo
Tag	Optional label used to categorize or classify the outlet	No	Tag

Table: Edit fields in the Outlets Identification groupbox and Description tab (mss_Outlet)

 

Figure: Outlets Description tab

Hydraulic Properties

Specify geometric and hydraulic parameters for outlets on the Geometry tab.

 

Figure: Outlets editor Hydraulic Properties tab

Edit field	Description	Used or required by simulations	Field name in datastructure
Flap Gate	Option for adding a flap gate preventing backflows	Yes	FlapGateNo
Type	Outlet Type: Tabular/depth, Tabular/head, Functional/depth, Functional/head	Yes	TypeNo
Height	Minimum water depth at upstream node for outflow to occur	Yes	Height
Coefficient	Coefficient of power function that relates outflow to head across the outlet for a Functional outlet	Yes, if Outlet Type is Functional	Qcoeff
Exponent	Exponent of power function that relates outflow to head across the outlet fir a Functional outlet	Yes, if Outlet Type is Functional	Qexpon
Q-curve ID	ID of rating curve with outflow rate as a function of head across the outlet for a tabular outlet	Yes if Outlet Type is Tabular	QcurveID

Table: Edit fields in the Outlets Hydraulic Properties tab (mss_Outlet)

Outlet types are based on how flow is computed as a function of freeboard depth or head across the outlet:

• Tabular/depth. Uses a tabulated curve of flow-freeboard depth values.
• Tabular/head. Uses a tabulated curve of flow-head difference values.
• Functional/depth. Uses a power function \(Q = \text{Coefficient} \cdot y^{\text{Exponent}}\) where \(y\) is the freeboard depth above the outlet's opening.
• Functional/head. Uses a power function \(Q = \text{Coefficient} \cdot y^{\text{Exponent}}\) where \(y\) is the head difference across the outlet.

An outlet can have a flap gate which restricts flow to only one direction and prevents backwater flow.

The flow through an outlet is determined by a user-supplied function or table of flow versus head difference across the outlet (Q-curve ID). This flow can be controlled dynamically through user-defined control rules.