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Dear colleagues
In urban areas, the underground hydraulic network is composed by a lot of underground channels or pipes with different sizes one after the other.
For example, we can have 3 circular pipes of 1m of diameter, after two rectangular pipes of 1.5X1m...
I want to know if I can associate at the same point the outlet of the 3 upstream pipes and the inlet of the 2 downstream pipes.
Sometimes, the junctions are under buildings. So, the topography of the 2d mesh is upper than the Z1 and Z2 value we have to define in the culvert options of Telemac2D. Does it work?
If needed, I think to decrease artificially the topography on the junction.
Thanks for your advices.
Best regards
Frédéric

Hello Frédéric,

My experience in culvert modelling is very low. I would have said, let's try and feel free to share your experience if it works or not.

It does not seem that other users have any feedback to give, but I would be interested in reading any.

Chi-Tuan

Hi

We have integrated a lot of buses in different models and we have very bad results of discharge.

Perharps, we don't use the good way.

An example:
We have a channel of 5m x 3m with grid of 1m.
The channel is after undergound and we create a buse of 5 x 3m.
The exit of the buses is in a channel of the same size.
We hope to have a discharge of 50 m3/s

The discharge simulated is very low even if all the head loss are zero.

We don't know if the size of the buses needs to be lower than the size of the mesh.

We try to modify the bathymetry and put nodes of the buses a little deeper but there is no change.

Perhaps, Type 1 "Critical depth at inlet- supercritical flow inside the culvert" is not avalaible and it could be the case.

If someone have an idea. we can share an example the next week.

Best regards
Frédéric

Hi!

From what I understand, I think you are willing to use the culvert function outside of its intended use.

The principle of the culvert function is that it computes a discharges through a culvert depending on:

• Invert elevations and water levels and US/DS nodes – water levels are computed with standard SWE in 2D domain
• Head and friction losses along the structure
• Inflow is simulated as a sink point, outflow as a source
• Only one-to-one configuration, that is a single inlet linked to a single outlet (in standard version – modifications might work)

This implies that it is impossible to put two culverts one after the other, especially if willing to use the same node for outlet US culvert and inlet DS culvert, and expect reasonable results.

Another aspect that is important to keep in mind when modelling culverts is that the the discharge through the structure is limited by the available volume in the US cell. Discharge limitation can occur if using a combination of small cell size (eg. small available volume) and large time step (can often be a problem in FE but never is a problem with FV as time step is often small enough).

Regarding the issue about the culvert not behaving as expected in a channel configuration. As described in the principles above, I wouldn’t use a culvert to model a structure that spans over an entire channel. The discharge calculations will be highly dependent on the water elevation at inlet/outlet nodes which will be automatically wrong as those nodes are expected to have the same capacity than the whole channel. There is a high risk that this creates a critical section for example, thus spoiling the results.

Hope it helps!

Kind regards
PL