Adding 2D conduit and 2D linear drainage features

2D conduits can be used in a 2D simulation to introduce unidimensional hydraulic structures directly in the 2D engine, and allow flow to be transferred between two areas of a 2D zone.

A conduit is defined as a 2D conduit if its type is Conduit (2D) or Linear Drainage (2D):

The Conduit (2D) type represents a drainage structure such as a culvert, which may be located beneath a road. In addition, momentum is preserved in the 2D conduit/2D zone connection, providing a better representation of the actual flow for this type of hydraulic structure. Since 2D conduits are sub-divided into a series of computational cells, small conduits will introduce small elements into the model, which could dramatically increase the run time.

The Linear Drainage (2D) type represents a linear gully, such as a slot drain, which is connected vertically to the 2D surface. A typical modelling scenario for this functionality is detailed drainage site projects, where the 2D modelling resolution is 100m2 or less.

In this example, conduit 2D links and connect 2D nodes have been used to represent an underpass that forms an important flow route. This allows the flow under the embankment to be represented within the 2D engine. Momentum will be maintained and volume balance issues between the 1D and 2D engines can be avoided.

1. Double-click one of the nodes to open its Properties window.

The Node type is set to Connect 2D, and the Connection type is set to 2D, allowing direct connection between the conduit 2D link and the 2D element. The same node and connection type are used at both ends of the link, to allow flow to be exchanged with the 2D zone at either end.

2. Open the Properties window for the conduit connected between the two nodes.

The Conduit type is set to Conduit (2D), which limits the available options.

The location of the nodes should be sighted:

3. In the Windows toolbar, select New 3D network window to open a 3D window.
4. Ensure that there is good agreement between the 2D element - ground level and conduit (2D) upstream and downstream invert levels.

Adjustment of locations can be made after the mesh is generated, as adding a conduit (2D) link does not require the mesh to be regenerated—although adding a linear drainage (2D) link does require regeneration.

5. Review a simulation of this area.

The flow can pass under the embankment represented in the 2D element levels, through the conduit (2D) link, and out onto the 2D elements on the other side. This means that if the depth reaches a sufficient level, the embankment can be overtopped via the 2D elements.

Because the conduit (2D) link uses momentum as part of the boundary condition for the conduit, it has been found to perform poorly in areas of deep and stagnated water. If this condition occurs in the model, it may be necessary to use the outfall 2D and conduit type links for a better hydraulic representation.