open TELEMAC-MASCARET The mathematically superior suite of solvers

Hello,
I work on a project of dispersion the waste water rejected by an emissary and i want know what the expression of the law of tracers degradation used in 2D or 3D telemac .
Thank you
Best regardes

Hello Ayoub

As described in the user manual, Telemac-2D can consider exponential degradation laws. This can be activated by the use of the keyword LAW OF TRACERS DEGRADATION. The default value is 0 (which means no degradation), you can activate exponential degradation by using 1 for every tracer.
Moreover, you need to add the following keywords
COEFFICIENT 1 FOR LAW OF TRACERS DEGRADATION : time to consume 90% of the initial mass
You can edit the subroutine difsou.f (sources/telemac2d) if you want to add your own law.
For Telemac-3D, there is no pre-implemented law, however, there are several commented examples in subroutine source_trac.f (sources/telemac3d) that can help you to introduce your own law.

I hope that this helps.

with my best regards

Riadh ATA

Thank you Riadh for your quick reply,
I wanna to know is that expression is implemented in telemac 2D when i activated the keyword LAW OF TRACERS DEGRADATION in telemac 2d ?

Hello

Yes the law is implemented but you need absolutely to give the value of the keyword COEFFICIENT 1 FOR LAW OF TRACERS DEGRADATION.
There is no default value for this keyword, I think that we should introduce it in order to avoid strange behaving of the code.

with my best regards

Riadh

Hello Riadh again,

I'am asking if there is a keyword about the density of tracer
because I want to simulate the dispersion in telemac 3D (20m depth in the see).
the sea water has a density of 1020 Kg/m3 (as mentioned in the manuel of telemac 2d) greater than my effluent which has a density of 995 Kg/m3,
so my effluent will tend to asend to the surface !!!!!!!

Hi
If you're in 2D, this mean average on the vertical so you can't take in account the buoyancy of the effluent.
If you really want to take this phenomenon into account, you should make a 3D simulation

Regards

Hello,

In fact it is not programmed like that, the density is for the water only, depending on the temperature and the salinity, or on a tracer, which is your case. What you have in mind would be rather a 2-phase flow. The way to take into account a tracer with a different density would be to use the density law number 4, and give the corresponding coefficient BETAC. The subroutine computing the density is drsurr.f in library telemac3d, you can see there how it is implemented and the definition of BETAC, it is also in the documentation.

With best regards,

Jean-Michel Hervouet

Hi

To moderate Riadh's answer, I should say that the implemented law is not the one you indicate in your attachment.
The implemented law is:
C(t) = C0 exp^(-kt) with k = 2.3/T₉₀

regards

Hello again,

in the law 4 for LOI DE DENSITE What's mean exactely VALEURS DE REFERENCE DES TRACEURS (i suppose it's the initial concentration of my tracer !!!!!! )

With the best regard's
Ayoub

Hello,

No, it is not the initial value, it is the reference value used in the definition of BETAC.

Regards,

JMH