Unsteady flow computation with juntions

[Jvaridel]

I am trying to run an unsteady flow calculation and I have problems with junctions. In my model I have 5 junctions and during the calculation one junction create instabilities and stop the simulation. All junctions have been created using the same method. Can somebody give me some tips? Thanks

 

[gbam]

Jvaridel;
I am not that versed in the unsteady regime but from a logical approach; Have you tried to model one at a time? For instance begin with the upstream most junction and model that so you can check results. Then add a new downstream junction to your moodel to see if something jumps out in your modeling. Are these diversions or confluences? If they are diversions then you can model them externaly and input a rating table or something. Hope that helps.

 

[cvg]

it might help if you stated what software you were using or what error messages you were seeing.

 

[Jvaridel]

Oh I am sorry...I have forgot to mention the name of the software! So, I am working with HEC-RAS 4.0.

I have already try to disconnect all the reaches and with this configuration no problem occure. And after I reconnect one junction at a time until I found wich junction create the instabilities.

All junctions are confluences.

The problem comes at the beginning of calculation just after one time step and the message is "matrix solution failed".