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Hi,

I am using the ES harmonic constant solution from OSU to force open boundary conditions.

The OSU solutions have data for sea elevation and velocities, but my understanding is that only sea elevation data have been calibrated and validated? If I would like to use only the sea surface elevation solution and not consider the velocity database, how could I do that? In my first attempt I excluded from the steering file the "binary database 2 for tide", but didn't work. In my second attempt I have defined my boundaries in Blue Kenue with only a prescribed sea elevation. The second option worked but the results did not change at all from the case where sea elevation and velocity databases were included.

Thanks for your help.

Alberto

Hi Alberto,

The type of tidal boundary conditions is determined by the arrays LIHBOR, LIUBOR and LIVBOR that correspond to the first 3 columns of the boundary conditions file (the one you may have generated from BK). In your case, in can use 5 4 4 (prescribed sea levels and free velocities), 5 6 6 (prescribed sea levels and velocities) or 4 6 6 (prescribed velocities and free sea levels).
Can you send the boundary conditions file, steering file and Fortran file (if you have changed anything) please?

If you can read French, there is a French manual describing how to use harmonic constants files to prescribe conditions for open boundaries:
www.opentelemac.org/index.php/training-and-tutorials

If you cannot read French, you can read the following posts and the enclosed documents:
www.opentelemac.org/index.php/kunena/16-...h-v6p2?start=10#6080
www.opentelemac.org/index.php/kunena/16-...-condition-file#7000

Regards,

Chi-Tuan

Hi Chi-Tuan,

I think you answered my question. In my case I need to define the boundaries as 5 4 4 (prescribed sea levels and free velocities) and set up thompson to resolve the velocities at the boundaries?

Find attached the steering and bc files




Thanks,

Alberto

Hope this time works...

Hi Alberto,

If you only want to prescribe sea levels at open boundaries, you are right, you have to use the 5 4 4 code in the boundary conditions file.

If you use the default option for OPTION FOR LIQUID BOUNDARIES (= 1), sea levels are prescribed as a Dirichlet condition, and that may lead to a not well posed problem.
If you use the Thompson conditions, the boundary conditions may be more physical (in particular for entering waves). Nevertheless, it is more CPU time consuming, and is a bit more unstable: some spurious oscillations may appear, that is why using a FREE SURFACE GRADIENT COMPATIBILITY coefficient lower than 0.9 (or even lower) may be necessary.

Hope this helps,

Chi-Tuan