open TELEMAC-MASCARET The mathematically superior suite of solvers

Hello,
I ran tests in 2d and used the free surface measured data to calibrate the model. Then I switched to T3D and wants to validate my 3D model.
I was expecting the free surface flow to be almost the same as my T2D model.But it seems T3D model gives higher free surface than the T3D(but more in agreement filed data).
I am just wondering what causes this discrepancies.
I should mention that I have the TPXO boundary forcing data. the water levels at the offshore are also different between the T2D vs T3D. Greater water levels resulted with 3D hydrodynamic.
I attached here the two CASs files I used for the Telemac 2d and Telemac 3D.
Also screen shots of free surface in the area of the project and offshore area and water level at the offshore area.

Your help is very much appreciated!
Sanaz

I don't understand why the offshore water levels are not the same. Should not they correspond exactly the TPXO database!

Hello Sanaz,

What are the units of your y-axes in your figures, meters? For free surface, with respect to what the bottom elevation is related, Mean Sea Level?

Using OPTION FOR LIQUID BOUNDARIES = 2 (Thompson boundary conditions) does not prescribe exactly the water levels at the boundary conditions you give as input. If you want to prescribe exactly water levels at your boundary conditions, you should use the classical boundary conditions (OPTION FOR LIQUID BOUNDARIES = 1) and codes 5 4 4 in the BOUNDARY CONDITIONS FILE (LIHBOR = 5 prescribed water depth, LIUBOR=LIVBOR = 4, free velocity).

Anyway, can you show a figure of the extent of your domain with scale (e.g. longitude/latitude or a projection with scale)?
If using Thompson boundary, it is recommended to have boundaries almost perpendicular to the velocity currents.

The NUMBER OF BOTTOM SMOOTHINGS may change the water levels in your domain.

Moreover, you should clean your TELEMAC-3D steering file:
- some options are inconsistent (e.g. NON-HYDROSTATIC VERSION = NO and DYNAMIC PRESSURE IN WAVE EQUATION = YES),
- if modelling temperature and salinity and you want to see stratification or buoyancy effects, it is strongly recommended to use the NON-HYDROSTATIC VERSION (which is the default value),
- some default values for some keywords should be used first before tuning your TELEMAC-3D case. I recommend you to have a look at what my colleague Agnes has already written : www.opentelemac.org/index.php/kunena/21-...se-with-some-figures
(IMPLICITATION FOR DEPTH = 0.55, IMPLICITATION FOR VELOCITIES = 0.55, SCHEME FOR ADVECTION OF... = 5 + SCHEME OPTION FOR ADVECTION OF... = 4 but also MINOR CONSTITUENTS INFERENCE = NO, NON-HYDROSTATIC VERSION = YES). When you change the default values, you should wonder the signification of the keyword and why you want to change it.

If you want ot compare your T2D and T3D model only for water levels, I would advise you to only compare tidal and hydrodynamics options.

As already written in a previous post, tpxo 9 includes 2 extra tidal constituents (2N2+S1) compared to previous versions and currently, TELEMAC does not take into account the S1 constituent as written in a warning message that you showed.
Did you have a careful look at the output file in particular before the first time step and at the final step just to be sure there is no warning from TELEMAC?

Hope this helps,

Chi-Tuan

Thanks alot for the comprehensive reply.I implemented the suggested tips and results were improved.

Thanks a mil,
Sanaz