open TELEMAC-MASCARET The mathematically superior suite of solvers

Hello everyone,

I set up a 3D HN-modell of a river which takes one active tracer (salinity) into account. Fresh water streams into the modell domain at one boundary and water level changes at the second boundary. At this second boundary, I defined constant salinity as well.
In the first computation, I set the salinity to 20 psu and in the 2nd computation I set it to 30 psu. It turned out, that the water level increased in a range of approx. 5-10 cm.

Could anybody please explain for what reason the water level is rising?

I understand that salinity affects density and density has somehow influence on the velocities and waterdepth.
But how exactly does density influence the momentum equations and how does it lead to a rising water level?

Thank you very much in advance!

Kind regards,
Calais10

Hello Calais

You need to look at the user manual of telemac3d where everythings are well explained. The answer to your question can take much more than a post on the forum
Just to sum up very briefly, the density variation is taken into account in the momoentum equation as a buoyancy force. this is based on the theory of Boussinesq approximation (mainly, the variation of density is very small compared to the density values itself).

You will have much more details in the J.M. Hervouet book, in the documentation of Telemac-3D or in any good book of free surface hydraulics.

with my kind regards

Riadh

Thank you very much so far. In the meantime I read some pages of Mr. Hervout's book "Modelling of free surface flows". Refering to you suggestion: That's right and I figured these facts out, too, which where briefly described in the Telemac manual.
Finally, this question will be a topic for another masterthesis.

With my kind regards,
Calais10