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Hi,

I am trying to generate a mesh with edge length as a function of bathymetry. I have been following the instructions given in the 'Tutorial Manual for teh Mesher in Blue Kenue on page 19, with the following steps:

1. Select the object Mesh_04 with its bathymetry attribute.
2. Tools – Calculator.
3. In box A, enter 275, (assign 275 to variable A (Fig.20))
4. In box B Select Mesh_04 (assign the node value of Mesh_04 to variable 5. In the Expression box, enter A-B • In the Result Name box enter the name of the new variable Mesh_06, then its units m
6. Click on Evaluate. A new object Mesh_06 is created (here it is a t3s mesh similar in shape to mesh_04.
7. Select Mesh_06, and Drag into Maillage_01/Density. The Mesh_06 node values will now be used to specify the density during the meshing process Maillage_01
8. Keep the polygon ZoneDigue_5m in Maillage_01/Density to impose the small elements around the jetty. If the polygon is removed from Density, the triangle size around the jetty will bedefined only by the bottom elevation.
9. Double-click on Maillage_01, check that the Default Edge Length is still appropriate (the triangles size may change significantly), then Run to generate the new mesh. Rename it Mesh_07.
10. Drag Mesh_07 in the window 2D View to visualize the results. Check that the resulting
mesh looks like what we were looking for.
11. Repeat the above mapping process to interpolate the bathymetry data onto this latest mesh Mesh_07 and create a new attribute Bathy_01.

However when I get to step 9 I am slightly confused by what to choose as the default edge length, as surely this is defined by Mesh_06 to specify the mesh density during the meshing process. Essentially my bathymetry varies between zero and -5000 and I want the mesh size to be approximately 1000m at the coastlines in shallow waters and 15000m in the deep waters.

I tried keeping the default edge length at 15000m, however when running this to generate the mesh the edge length throughout the domain was consistant at approx. 15000m. I also tried reducing this to 1000m, however this takes too long to process, suggesting that an edge length of 1000m is being used throughout the domain.
Any help with how to define the default would be greatly appreciated.
Kind regards
Danny

Hello Danny,

What I usually do is set the default edge length as the largest desired length in my mesh and let the density function refine it from there.

In your case, bathymetry varies from 0 to -5000 and the desired edge length is ranging from 1000 to 15000. An appropriate density function would be:

-2.8*(Bathymetry)+1000

Depth is 0 -> Edge length is 1000
Depth is -5000 -> Edge length is 15000

Put 15000 as the default edge length and you would be good to go.

Regards,
Costas

Thanks Costas, that has worked perfectly.