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Hi, I'm new learning telemac 2d.

What should be the boundary conditions for supercritical and subcritical flows ?. There is some problem in placing only the flow or level.

regards

Hello

This topic is widely discussed in the forum, you can browse the topics dedicated to these issues.
What you have to know mainly, is that theoretically:
1- for subcritical inlet: you need only one condition (discharge or elevation)
2- for subcritical outlet: you need only one condition (discharge or elevation)
3- for supercritical inlet: you need two conditions discharge and elevation
4- for supercritical outlet: you need nothing.

It is recommanded to choose the extend of your model in order to keep always a subcritical regime for inlets and outlets. There are some exceptions that you will descover with a more expert use of hydraulic models.

with my best regards

Riadh ATA

thank riadh,

In case of supercritical, how should I define the border ?, can define a level even if it is not needed?

Yes You can give an elevation for instance.
Don't forget that you are not able to know a priori if you will be subcritical or not. The best way to do is to choose a smart location for your boundary (with smooth bathymetry and with a straight (not curved) boundary) and to prescribe a rasionable boundary condition in case where the flow comes to be subcritical.

with my kind regards
Riadh

Hi,


I have a new question.
In case of subcritical it is possible to place in my boundaries, the same type of condition, that is to say, inlet condition discharge and outlet condition discharge.
I try to put in my discharge and discharge discharge (negative) and the following error occurs in bondary outlet:

"GIVE A VELOCITY PROFILE IN THE BOUNDARY CONDITIONS FILE OR CHECK THE WATER DEPTHS. OTHER POSSIBLE CAUSE: SUPERCRITICAL ENTRY WITH FREE DEPH IN THIS CASE GIVE A POSITIVE DEPTH IN THE INITIAL CONDITIONS OR PRESCRIBE THE DEPTH AT THE ENTRANDE."


If it is possible to use the same discharge condition, for continuity the volume of control in study in theory would not vary, but the program is adjusted and varies in the beginning to be able to reach equilibrium?

Hi,

I already tried it and I have not had problems.

However this problem occurs when the discharge is equal to zero at the boundary indicated, this because of the water depth or the velocity (whichever could be 0), which happens when the model is not well-possed. You should check if there is a node from that boundary that could be dry (water depth equal 0), so, verify if the initial condition makes that your boundary has a positive water depth.

Hope it helps,

Cheers,

José

hi jose,

Could you send me your code as you used it? Check that there are no delph = 0 in my code.

Thanks

Dear Joaquin,

Please find in the link below my files.

drive.google.com/open?id=0BxYwOb2RaOSfU04yX1NWb01EZ3M

PS: I tried with different values at downstream and it works fine.

Cheers,

José

Thanks a lot for sending me an example, the problem is that in your example the slope is 0, it makes the behavior totally different, in fact, I think its control volume is constant. I wanted to know if in the case that obviously the control volume is not constant (initial condition of delph very high for example) and to put a constant Discharge in the inlet and outlet of equal way reaches equilibrium.

Cheers

Joaquin