open TELEMAC-MASCARET The mathematically superior suite of solvers

Dear all,

I am trying to use Blue Kenue in order to build a simple triangular mesh. As a first try, I generated a 2D matrix in matlab representing a rectangular domain with evenly spaced bathymetry data. I exported this into a point set .xyz ascii file that I later imported in Blue Kenue. The thing is, even though I read the manual and went through the different posts in this forum, I am still not really sure about the steps to follow in order to build a mesh based on those bathymetry data. Could you give me a quick protocol on how to proceed ?

Based on my understanding, I did as follows:
1. I loaded the point set .xyz file
2. I drew an outline (contourline) of the mesh I want to create
3. I triangulated the data, using File -> New -> Triangulation in which I used the outline as constraint line for the triangulation
4. I generated the triangular mesh by means of the T3mesh generator where I dragged the outline in the outline object before clicking on the "run" button
5. (I am not sure if I need to do this). I mapped the triangulation on the newly created triangular mesh using Tools -> Map object -> and select the triangulation object
6. Using File -> New -> 2D Interpolator, I interpolated the point set object (i.e. my bathymetry data) and used again the outline as constraint outline.
7. I mapped this new interpolation onto the mesh using the "map object" options in the tool menu

The result is pretty coarse compared to the spatial representation of the original data in the .xyz point set file. My question is do I have to triangulate the data or not prior to interpolate and map them onto the mesh? And what is the difference between doing triangulation of the data and interpolation of the data? Also, my bathymetry has some negative and positive values and I read somewhere in this forum that z must be strictly positive, isn't it ?

Thank you for your clarity.

Jean-Philippe

Hi Jean-Philippe,

I think you are mixing up the 2 stages of generating a mesh.

Step 1 involves the creation of a mesh starting from an outline and constrained variously by adding hard & soft lines, hard points, submeshes etc. Use the density object to control the spatial resolution of the mesh. You can supply polygons (areas of constant edge length), pointSets from which the edge length is interpolated, etc.

Step 2 is where bathymetry is applied (mapped) to the mesh.

"File->New->T3 Mesh Generator" is where you want to start.

"File->New->Triangulation" simply generates a delaunay triangulation of some source data.

Once you have generated a proper mesh then you can use the Interpolator as source data for mapping bathymetric data.
Alternatively if you have already triangulated your regularly spaced bathymetry (using "File->New->Triangulation" as you stated) you can use "Tools->Map Object" straight away. (This basically achieves the same thing as choosing "Linear" as the interpolation method.)

The BOTTOM/FOND variable can be both positive or negative (positive is up). WATER DEPTH/HAUTEUR D'EAU must be positive.

If you read French have a look at the excellent Blue Kenue tutorial that Philippe Maron posted here last week. It is pinned to the top of the Blue Kenue topic.

... Martin

Ok. Thanks for clarifying.

Yes, I took a look at the tutorial and it was really helpful. Very good initiative!

Cheers,

Jean-Philippe