1d pits empty despite pipes running full

[Melodea 0]

Hi All,

 

I have a few pits in my pit/pipe network that are showing zero flow into the pit (according to the TS layer), however the CCA layer is showing the pipes are running full.  I used the SA_PITS method to input the flow directly into the pits.  Has anyone else seen this before?

[Mitch3007 0]

Hi Melodea, 

There are a few things that may be happening. Can you please send me through a few levels to help pinpoint what the problem may be:

• What is the 2D cell ZC level at one of the pits where you are getting no flow?
• What is the QH relationship you are using for that particular pit?
• What are you specifying for your pit upstream and downstream invert levels?
• What are you using in theConn_2D attribute of your 1d_nwk or 1d_nwke file at the pit?
• What is the pipe invert level at the upstream end of the downstream pipe?
• When the pipes are running full, what is the water level in the _TS output file both at the pit and at the upstream end of the downstream pipe?

If the hydraulic grade line is close to  surcharging into 2D, this may result in zero or even reverse flow. Please let me know the above. If it's easier for you,  I might get you to send it through to support@tuflow.com. I can then post it back up onto the forum. Kind regards, Mitch. 

Edited October 20, 2015 by Mitch3007

[Melodea 0]

Hi Mitch,

 

Thank you for your response, I have posted my answers to your questions as well as some screen shots to support@tuflow.com as you suggested.

 

Thanks,

Melodea.

[rachel.jensen 0]

As a forum follow up, the reason why there was flow come straight into the bottom of the culvert is because of a 1d_bc layer.
The model had a polygon in this layer as a QT type, refer to table 4.30 on page 4-141 of the 2010 Tuflow manual for more information.
As the manual describes, this equally distributes the flow hydrograph defined in your BC database to the nodes in the region. Nodes that link to the 2D (the pit connections) are not included in this. Thus, no flow at the top of the pit, hydrograph applied at the bottom.