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Hello,

I have built a model for my studied area, the mesh built is presented in the file « model » (see image below).

There is two principal boundaries :

• a liquid boundary with an imposed flow on the upper side of the mesh (in light blue) ;
• a simple liquid boundary for the rest of the domain (in black).

The flow is defined as following :

• from T= 0 s to T = 7200 s, the flow is increasing from 5 to 148 m³/s ;
• from T = 7200 s until the end, the flow is constant and equal to 148 m³/s.

I have created control sections to check if the flow in my domain is correct. The first control section (in pink) is right after the entrance of the model, so the flow there should be 148 m³/s once the permanent flow is reach. When I have checked the window « command » after 2 hours of simulation (so just at the begening of the permanent state), the flow in the first control section was 251 m³/s. On the next iteration, the flow went down to 197 m³/s.

You can find there the message.

Why the flow is higher than the inflow imposed on the upper boundary ? And why the flow is changing so fast ?


Thank you for your help !

Hello

This is simpy because you are far from the steady state. If you look at the flux trough your two boundaries you will see that both values are negative. This means that water still leaving the domain from both boundaries.
Steady state will generate the same flowrate which is entering (positive) from the input side and going out (negative) from the output side.

You may run the model much longer to reach such a steady state. This is probably beacause your initial conditions are far from being physical conditions.
A final remark, the output boundary is very large, why is it not confined to the main channel of the river.

I hope that this helps

with my best regards

Riadh ATA

Thanks for the answer !

The ouput boundary is very large because it looks very probable than some water go away from the main channel of the river because of the nearly flat topography.

JP