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Hello,

I am studying a part of an estuary in a 2D model. I include 1 tracer in my model, being salinity (kg/m3). I have the following boundary conditions:
- upstream: imposed time series of discharge & salinity (BC 4 5 5 0 0 0 0 4)
- downstream: imposed time series of water level & salinity (BC 5 4 4 0 0 0 0 4)

When I check the results of my simulation, everything seems fine from point of view of hydrodynamics. However, there seems to be a problem with the calculated salinity. The calculated salinity at my model boundaries doesn't correspond to the imposed salinity values here. There is an increase of the salinity at the upstream boundary, while the downstream boundary more or less remains constant, despite the imposed tidal variation.
I tried to adapt different parameters in my cas file (SOLVER FOR DIFFUSION OF TRACERS, COEFFICIENT FOR DIFFUSION OF TRACERS, TURBULENCE MODEL, VELOCITY DIFFUSIVITY, ...) however the results always remain similar at the boundaries.

I assume the problem has to do with my parameter settings, however I don't see what is the exact reason. I would be happy if anybody could help me with this problem.

I include the following information in attachment:
- cas file
- figure with salinity at downstream boundary (imposed + calculated)
- figure with salinity at upstream boundary (imposed + calculated)

Thank you very much for your help.

Best regards,
Stefaan

Hi Stefaan

I think your problem comes from the boundary condition file. The value 4 for the tracer means free value so you probably need to have 5 instead of 4 for the tracer...

Hope this helps

Hello Christophe,

Indeed, it was the tracer specification in the boundary condition file. Thanks a lot for your answer!

Best regards,
Stefaan