open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi, all.
I am modelling a steady flow of 17500 m3/s using the equations of finite element. The result of the velocity is unstable. The velocity, especially at the input is unreasonable as shown in Fig. 1. Moreover, the output discharge unstably varied around 17500 m3/s, which can not reach exactly the same as the input flow (17500).

Then, I tried to use equations of finite volume. The result from finite volume is reasonable as shown is Fig. 2 but flux at output was unstable (Fig. 3) although a steady flow was given at input.

Maybe there's some problem such as boundary condition of water level given at the output was not compatible with the geometry. Or maybe some other reasons.
Two unzip file of finite element and finite volume have been upload respectively. Can anyone help me? Thanks.

Hi!

For FE you need to optimize your set-up. Look at the user manual, there are recommended options for river flow.

I got good results when adding the following keywords:

TREATMENT OF THE LINEAR SYSTEM =2
TYPE OF ADVECTION=1;5
CONTINUITY CORRECTION =true
H CLIPPING = NO
MASS-LUMPING ON H=1.
SUPG OPTION = 1;0
TIDAL FLATS = YES
OPTION FOR THE TREATMENT OF TIDAL FLATS = 1
TREATMENT OF NEGATIVE DEPTHS = 2

Another thing is that I don't understand why you want to disable advection? I removed those keywords in my test.

Hope it helps!

Kind regards
PL

Hi, pilou1253. Thanks for your kindly reply.It's a mistake that the advection term was set to be disabled. The keywords you suggested help me a lot. The modelling is reasonable now.