Choose connection node storage area

A connection node is a schematisation object that connects channels, pipes, culverts, weirs, orifices and pumping stations. Storage can be added to these nodes by setting the storage area to a non-NULL value. This section provides guidelines for choosing the right storage area.

Manholes in sewer systems

In sewer systems, the storage area corresponds to the surface area of the bottom of the manhole. If no data is available on the manhole dimensions, a storage area of 0.5 to 1 m can be used as a sensible default in most sewer systems.

Effect on advection

If the (square root of the) storage area is much larger than the width of the channels or pipes connected to it, it will reduce the advective force: fast-flowing water that flows into a large storage will loose its momentum and not pass it on to the next channel section or pipe.

Storage area at channel junctions

The loss of advective momentum also occurs at channel junctions, because of the turbulence and still waters present at these locations. Adding a storage area corresponding to the size of the junction will lead to more accurate computation of the advective losses of the flow.

Pumping stations

A pumping station’s start connection node should be sufficiently large in comparison to the pump capacity. If you do not have data on the dimensions of the pump cellar, choose a realistic value based on how fast the water level is expected to lower as soon as the pump turns on. E.g., if the pump capacity is 3000 L/s, a storage area of 2 m:sup:2 would lead to a drawdown of 1.5 m/s, which is not very realistic. A storage area of 20 m would be more realistic in this case.