open TELEMAC-MASCARET The mathematically superior suite of solvers

Hello,

I created a mesh in Latitude and Longitude for use with TPXO data.
I have; however, used the mesh with a different method (simulating the tide by changing the water level at a liquid boundary).

I created the .slf with Blue Kenue and the XYZ file looks something like:
-68.306031 44.292780 -14.3256
-68.308565 44.292626 -11.8872
-68.310642 44.292580 -10.668
-68.310565 44.291390 -11.5824
-68.311362 44.293141 -7.62

As you can see, the X and Y coordinates change with the second or third or fourth decimal.

Now, I have a question:
When I run the analysis WITHOUT TPXO data, I set the GEOGRAPHIC SYSTEM = -1 .
Does this mean that TELEMAC sees the X and Y as meters and so my fjard would be only centimeters wide and meters deep (essentially a crack in a rock)?
Should be putting GEOGRAPHIC SYSTEM = 1?
When I look at it in Blue Kenue, the BOTTOM mesh looks great and well proportioned, but the color scale for the FREE SURFACE is quite large (to -7500).

Hello

The GEOGRAPHIC SYSTEM is for TPXO only. If you are not using TPXO it will have no effect.

TELEMAC will see the coordinates of your mesh as meters if the keyword SPHERICAL COORDINATES = NO (the default). If you are simulating in Lax X Lon you must use SPHERICAL COORDINATES = YES, otherwise yes, it will be a mesh a few centimeters wide.

Now about the value of the free surface, I have no idea. Check if you aren't using some kind of vertical transformation that is changing the bathymetry.

If you attach the simulation files I can see if I discover what's going on with the depth.

Best regards,

phelype

I made the changes and reran it, but the water level height still looks crazy in the results (the results file is 1.7 gigs, so I can't attach that).

Hello,

I tried to run your simulation here and I'm getting the following message:
This means that the boundary conditions you are imposing are not enough to make the solution possible (I think that in this case the number of solutions for the system is infinite) You have to add more boundary conditions to correctly represent your lateral boundaries.

I use Telemac3D, but I think that the principle is the same. The conditions I use are:
- Initial conditions:
-- Velocity field
-- Elevation

- Lateral Boundaries:
-- Velocity
-- Elevation

- Superficial boundaries:
-- Wind
-- Atmospheric pressure

I think that once you define your boundaries properly the simulation will work.

Hope this helps.

Best regards,

Phelype

Hi, Thanks for your help and your response.

I just have a few questions:

The basic overall goal of the analysis is to find the velocity of the water at a choke point in the fjard. The methodology I was trying to use was to increase the water level all along the boundary layer, which would create a wave flowing up the fjard (simulating the tide flowing in), and decreasing it would let the water flow out (simulating ebbing). The larger the increase over time, the faster the wave would flow up the fjard.
The question I pose is this: if the boundary needs a velocity field, and velocity is the required output, how does one simulate the tide based upon water height?
Or I could reword that as: what are the necessary boundary conditions if the desired result is to see the velocity of the tide?

I understand what you are trying to simulate.

Well, the sea level elevation due to tidal forces causes tidal currents in these regions, because the water will flow in/out with a velocity that depends on the velocity that the surface is moving and the section area of the inlet (that is, with a lot of simplifications).

As far as I can see, from the technical point of view, for your simulation you only need, as boundary conditions, the surface height and the velocity components at the inlet.

About your question "The question I pose is this: if the boundary needs a velocity field...". I think that, as I said previously (and Jean-Michel said here), that only the surface height is not enough for the system to be solved.

If your simulation is experimental (not based on real events), then use the mass conservation principle to calculate the inlet velocity field. Otherwise, try to get this data from somewhere (I use HyCOM).