open TELEMAC-MASCARET The mathematically superior suite of solvers

Hello,

I have been trying to compute the individual terms in the horizontal momentum balance equations using my model output following theoretical equations 2.3b and 2.3c in the manual, for a nonhydrostatic version of my Telemac3D model. My expectation is that at a single instant in time, for a single node, the terms in the momentum balance should sum to nearly 0. Because they do not, I suspect I am missing a term in the equations in my calculation, or misinterpreting the usage of an output variable of Telemac3D. The calculation of the terms has required much processing, including interpolation of my unstructured domain onto a regular grid, but at this point I am convinced my inability to close the momentum balance is not a consequence of a processing/calculation error.

Focusing on equations 2.3b and 2.3c, I have used the U, V, and W variable outputs in the local acceleration and advective acceleration terms on the left-hand-side. I suspect these are not the issue. I am using the sum of the dynamic pressure output variable (DP) and the hydrostatic pressure output variable (PH) to get p in the pressure gradient term. I calculated density from the salinity variable output (my TA1) assuming a constant temperature, because my model uses DENSITY LAW = 2. The next term that includes the kinematic viscosity, which I assumed to be the friction term, I calculated as attached, using the viscosities for U and V outputs from the model (NUX, NUY, and NUZ).

Lastly, the only source term I included was the Coriolis force, computed as -fV and fU in the X and Y balances. My model includes streamflow forcing at the boundaries and tides, but does not include wind.

My hunch is that I am missing a source term, perhaps a bottom friction term, or misinterpreting the friction term. I have attached my steering file. If someone could please take a look it would be greatly appreciated.

Thank you for your time,
Taylor

Hello,

As you ask specific questions about the equations, I would suggest to read:
- the TELEMAC-3D theory guide,
- the source code to know exactly what is done. It may help you find which term may miss you. The way to solve the Navier-Stokes equations is not so straightforward and not as simple as the equations written in the TELEMAC-3D user manual.

Hope this helps,

Chi-Tuan

Looking quickly to the steering file you provide, you seem to use quite an old release (7.2 or older).
Hard to help you.