SWMM - Links - Orifice

Orifices are used to model outlet and diversion structures in drainage systems which are normally openings in the wall of a manhole, storage facility or control gate. They are represented internally in SWMM as a link connecting two nodes. A hole can have a circular or rectangular shape, be located at the bottom or along the side of the upstream node and have a flap port to prevent back flow.

Holes can be used as storage unit outputs in all types of flow routing. If not connected to a node storage unit, they can only be used in Drainage Networks that are analyzed with Dynamic Wave flow routing.

The flow through an orifice is calculated based on the area of its opening, its discharge coefficient and the charge difference across the orifice. The opening height of a hole can be dynamically controlled via user-defined control rules. This feature can be used to model holding device openings and closings.

In order for SWMM to recognize a hole, the Constructor linear device, must contain an hole activity:

And fill orifice properties:

SWMM holes have, in addition to the properties of Links, the following properties:

• Orifice
  • Cross Section - Shape of the Cross Section, can be one of these types:
    • Circular - circular section, indicates the diameter of the section
    • Rectangular - rectangular section, indicates the width and height of the hole section
  • Discharge Coefficient - Discharge coefficient for flow through the central portion of the Weir
  • Retention Device - YES, if the Weir has a gate that prevents back flow, NO if not
  • Entrance Elevation - Entrance Elevation
  • Time to open/close - The time to open an orifice with the gate closed (or closed) in decimal hours. Use 0 or leave blank if timed opens/closes do not apply. Use control rules to adjust gate position
  • Hole Type - Hole Type:
    • Side
    • Background

To view the properties of the orifice in SOLIDOS, use the tab Properties or use the command SPROPS:

Note: You must click the at the top of the screen.

If it is not visible, it means that the network is not enabled for SWMM. Enable it in your properties: