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Hello,

I used TELEMAC-2D to set up a hydrodynamic model for Scheldt river. I used two open boundaries at upstream and downstream respectively. I ran it for 2 days and I got non-smooth time series of water level.



Besides, at certain time step, the velocities near the bank were larger that the velocities in the mainstream, which seems not logical.



I'm confused about these two problems. How could these happen? Does anyone have this kind of problems before? Thanks!

Hi
In my opinion, the initial condition is not consistent with the model so it takes time for the computation to propagate the boundary condition in your model.
Moreover, if you impose just the water level that could create some internal reflection which could generate small oscilations like those you obtain. And you could see those small oscillations seems to vanish during the computation.
So try to let your computation going further...
For the velocities, it will be intersting to have an overview of the bathymetry...
Regards

Hello,

I will add that you seem to model a dry bank with one element, in this case it is probably better to model it by a vertical wall, without bottom going up.

Otherwise you use the (correct) form of diffusion (1/h div(h nu grad(u)) which implies divisions by 0 on dry banks, so I would test the influence of this.

Otherwise I agree with Christophe, the period of these oscillatons may correspond perhaps to the time it takes a wave to go up and down in your model.

With best regards,

Jean-Michel Hervouet

Hello,

Thank you very much for your advice!

I modified the initial conditions and still wait for the result. But indeed imposing discharge at open boundary is a better choice.

I also changed the form of diffusion term into div(v grad(U)). Now the result looks better.I think it might be one of the reasons for giving larger velocities near the bank.



I looked at the bathymetry and it seemed that larger velocities near the bank had something to do with the slope because at those areas the slopes were very steep.