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Hi,
I am developing a model for an estuary site. A primary process of interest is the salt wedge intrusion. So far the model does a reasonable job at hindcasting water level as well as flood/ebb tide currents in the offshore region. However, during the flood tide, the modelled salt wedge only extends to 7 km upstream as opposed to
14 km.

1) I've tried a combination of smagorinky/constant/ke (horizontal turbulence) with ke/prandtl (vertical turbulence) and the salt wedge position of all the runs are fairly comparable.

2) I've also tried to use a large horizontal diffusivity value for tracer (50). The salt wedge position is still similar to other runs.

3) increasing number of layers also doesn't appear to have much impact on the salt wedge position.

Does anyone have thoughts on what I may have overlooked?

Thanks.

Hi,

The only things I can think of are:

1) Do other freshwater discharges into the system need to be modelled e.g. run-off/rainfall?

2) Are wind shear effects included/important?

3) Is the density equations of state included?

4) Are the effects of atmosphere-water heat exchange important?

5) Is the Coriolis force important over your length scales?

A picture of the results and your mesh could possibly help.

Hi,

Thank for the reply.

1) Do other freshwater discharges into the system need to be modelled e.g. run-off/rainfall?

On the upstream end, I have prescribed hourly discharge data from a gauge station.

2) Are wind shear effects included/important?

This could be for the dispersion of the freshwater plume in the offshore region but should not have influence on the saltwater intrusion extent (the channel is 15-20 m deep).

3) Is the density equations of state included?

Yes. I have "DENSITY LAW = 2" for salt.

4) Are the effects of atmosphere-water heat exchange important?

Similar to 2), given the extent of the tidal swing (3 m to 5 m) and channel depth (15-20 m), I don't think heat exchange is one of the primary processes in the system.

5) Is the Coriolis force important over your length scales?

Similar to 4, given the large tidal swing, I don't think Coriolis force would have much influence on salt wedge extent.

I am looking into the mesh. I do have roughly 6 elements to resolve the channel. Not sure further refining it will improve the results or not.

Hello,

Can you upload your steering file + potential Fortran files? Maybe they can give us ideas to suggest?

Chi-Tuan

I have attached the steering file here.

Hello,

Which release do you use? There were 2 bugs resolved in v8p2 for Thompson boundary conditions in 3D and velocity modelling for tides in 3D. So if you do not use the latest release v8p2r1, your results should be wrong.

I think you should then change some values of keywords:
- first one: NON-HYDROSTATIC VERSION = YES,
- it is strange that you do not give any value to keyword BOUNDARY CONDITION ON THE BOTTOM =

After changing NON-HYDROSTATIC VERSION = YES and upgrade to release v8p2r1 (if not already done), you can try TREATMENT OF FLUXES AT THE BOUNDARIES = 1;2;2
I would try k-epsilon in both directions and delete choices connected to mixing length model + reset COEFFICIENT FOR HORIZONTAL/VERTICAL DIFFUSION OF VELOCITIES to 1.E-6.

You can also read Appendix E of the TELEMAC-3D user manual to get some recommendations of options.

Hope this helps,

Chi-Tuan

I left out BOUNDARY CONDITON ON THE BOTTOM because the default value = 1 (LOG LAW FOR VELOCITIES ON BOTTOM).

I've conducted a run with v8p2r1, and with NON-HYDROSTATIC = YES and k-e turbulence model for both horizontal and vertical. The results are still similar. The open ocean boundaries are over 40 km away from the river mouth so bugs relating to Thompson boundary and velocity modelling for tides at the boundaries likely not have much impact on the salt wedge process in the system.