open TELEMAC-MASCARET The mathematically superior suite of solvers

I'm running a tidal simulation of a fjard. I have one liquid boundary with a prescribed H (see .liq). The height at the boundary changes sinusoidally, simulating the height change of the sea level with the tide.

The problem is, is that the results show some unrealistic behavior.

I was wondering if someone could weigh in on this.
Unfortunately, I can't attach my results file because it's almost 2 gigs.
I added some pictures with some mark-ups of problem areas.
It doesn't look like the water flows in at the liquid boundary area, but from a different point.

Attaching .liq and .slf in a zip.

Hello,

Just a guess but try to run with TIDAL FLATS = YES.

Your mesh have some nodes with very high altitudes and the initial elevation you are prescribing is 0.12 m. Maybe your problem is that these elements are drying out.

Hope this helps.

Best regards,

Phelype

Hello,

Think also that when you prescribe only the depth or the free surface elevation at an open boundary the problem is not always well posed. It is more or less correct when the flow goes out, but when the flow gets in, you lack information on the velocities, so a big eddy can enter your domain, and it is one of the infinite number of possible solutions (this stems from the theory of characteristics, with fluvial flows). In such a case of open boundaries in the sea we recommend to:

1) put this open boundary as far offshore as possible, i.e. with the largest depth and the minimum velocity.
2) use the Thompson boundary condition, that will deal with the characteristic pathlines to find, when possible, (flow exiting) the right boundary conditions.

With best regards,

Jean-Michel Hervouet

I made the changes (tidal flats = YES, Thompson boundary condition, and the open boundary is pretty off shore (I wasn't sure HOW much offshore it needs to be).

The results are still crummy and the behavior is all wrong.

Hello,

I would advise that you inspire from the test cases to enrich a bit your steering file.

For example choose :

OPTION FOR THE TREATMENT OF TIDAL FLATS : 1
TREATMENT OF THE LINEAR SYSTEM : 2
SOLVER : 1

Remove:
VELOCITY POFILES : 5
SPHERICAL COORDINATES : TRUE (is it really useful in your case ? not if your domain is less than 500 km large).

Then add a turbulence coefficient of 1. m2/s (VELOCITY DIFFUSIVITY if I remember well).
You should also add a bottom friction (at least it stops the velocities on dry land).

With best regards,

Jean-Michel Hervouet

OK, so I did all that.
When I run the analysis now, it just seizes up at Iteration 0.

Hello,

To start you can reduce the LISTING PRINTOUT PERIOD, that is the number of time steps to print information on screen.

Maybe your simulation is actually running but you don't see because of this keyword.

Best regards,

Phelype

I reduced at down and let it run. It still just sits there.

If you reduced to 1, then it is probably stalled at some solver. I would suggest changing the SOLVER or the MAXIMUM NUMBER OF ITERATIONS FOR SOLVER.