open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi,

I need en information

I need to know if is possible possible to enforce a fixed free surface level and have a free velocity on the boundary?
is possible to implement a transmissive boundary instead of the tidal boundary that I already tried?

Thanks so much,

Cristina

Hello,

Fixed free surface level and free velocity is the common practice for fluvial exits, for a boundary with entering velocities, it may cause problems.

For transmissive boundary we have the Thompson's boundary conditions.

With best regards,

Jean-Michel Hervouet

Thanks so much for your reply,

I'm new with Telemac and I never use the Thompson's boundary conditions.
I read the manual to find information about Thompson's boundary conditions, but I need know more details, and how can I use it.
Please can suggest me where can I read and learn more on it?

I really appreciate the help that you give on the forum, it is really useful.

Kind Regards,

Cristina

Hello,

Basically the Thompson's boundary conditions are obtained with the keyword :

OPTIONS FOR LIQUID BOUNDARIES : 1;2;2;1;1

this is an example with 5 liquid boundaries where only boundaries 2 and 3 would have Thompson.

On these boundaries you prescribed the data that are known and let free the data that are unknown, e.g. if you have on a liquid boundary measurements of depth and velocities you start corresponding lines in the BOUNDARY CONDITIONS FILE : 5 6 6
to say "prescribed depth and velocities", if depth is unknown put 4 6 6.
If you know nothing just put 4 4 4 (see the test case Thompson which works like that).
Then you are supposed to give your prescribed data in the subroutine bord.f, or to use a tidal model like tpxo.

This is to start with, with best regards,

Jean-Michel Hervouet

Hello,
I know how to use thompson's boundary conditions,but i want to know more information about it.Can you explain it in some detail or introduce me some book or article or web page about it?
Kind regards,
zqs

Hello,

It is explained in my book, or you can find the release notes of version 6.1, chapter 6, on this website, or in the last article of the proceedings of the 2011 user club.

With best regards,

Jean-Michel Hervouet

hello,

Thank you very much for your help.Now,i have another question:why ignore the variations along the tangent at the boundary?For the quantity is too little,or other reasons.

With my best regards,
zqs

Hello,

We ignore the tangent at the boundary because we can only deal with a 1D characteristics theory, the 2D theory is far too complicated, as pathlines become cones (but well, if someone wants to tackle this problem...).

With best regards,

Jean-Michel Hervouet