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Francis Lane

Extreme culvert depth

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We are modelling a fully submerged trunk drainage culvert with flood depth to invert > 7 m due to regional tailwater. There is hydraulic grade across the structure due to local upstream flows. Intitial water levels in both the 1d and 2d domain are set based on the regional tailwater. We have checked the time series results and the .eof file. At the beginning of the event, the water level in the culvert starts at the IWL/fixed tailwater condition, but then drops below by approx. 100 mm throughout the storm. Flow regime is 'F' (submerged entrance and exit, full pipe flow, downstream controlled), which is what we expect.

We do not understand how the head in the 1d domain can drop below the tailwater conditions.

We think the head drop at the outlet could related to the nodal area, as the automatically created nodal area table in the .eof stops just short of our fixed tailwater level.  Is there a quick way extend the automatically created nodal area table of a 1d_nwk culvert, or do we need to take an alternate approach via an NA table and 1d table link?



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Hi Francis,



You can use a node in the 1d_nwk layer to add a bit of storage.Refer to table 5-16 of the 2016 manual.

Using the Len_or_ANA, US_Invert and DS_Invert attributes, you can tweak the NA table that TUFLOW will create.


From the sound of the problem, it could be that the issue is complex and is influenced by a few things.

If, after looking into the NA options, you're still not sure where the head drop is coming from, feel free to email us the model at support@tuflow.com







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Thanks Rachel.

We will investigate the issue a bit more and see if we can work it out.

This particular model is quite complex. If we can't resolve the issue, we'll get some support. Mitch has looked at other aspects of this model previously.



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