open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi there,

in my TELEMAC 2D model (v5p9), I am using a rating curve as my river downstream boundary condition. I don't really understand how it is applied.

For example, in my rating curve I have :
Q Z
34.05 2400
34.72 2650

If TELEMAC apply well this rating curve, a discharge of 2500m3/s should always give the same Z, for every simulations ...
But it's not the case, for the same discharge, I have more or less 15cm on my water level ...

(I calculate the discharge and check the water level with Fudaa.)

So I feel TELEMAC give a random value when applying the rating cuve...
Am I right ? This is very troublesome.

Should I use a rating curve describing the Q(h) every cm ?

Thanks

Hi

The imposed Z is computed in the sta_dis_cur.f subroutine (fucntion), which is called by bord.f.
If you see at this end of this function, there is a relaxation factor (0.02) which gives the increment of Z to give to Telemac during this time step. So for an impoosed Q (Q=2500 in your example), it depends on what is your discharge at this time step. This latter, when varying, will induce different imposed Z. That's why you can find different Z for one fixed discharge.
The relaxation factor, I mentioned above, gives the possiblity to vary smoothly the boundary condition. You can change its value depending on the stability of your obtained solution.

My best regards
Riadh