FE mesh

Methodology

Building from scratch a new global finite elements mesh is a tedious task, hard to deploy inside an operational project. Therefore, and for pragmatic reasons, our approach has consisted in refurbishing the existing FES2004 global mesh with the three following objectives:

• increase shelf and topography slopes discretisation
• improve shorelines description
• keep mesh size at a reasonable level

Mesh construction

Entry: FES2004 FE mesh

FES2004 finite elements mesh

step 1: overall refinement for elements with size > 75 km

step 2: overall sanity and shape improvements (mesh-doctor tool):

diamond (interior vertices with 4 neighbours) elimination, over-connected nodes cleaving, triangles reshape

step 3 : regional refinement (mesh-upgrade tool) for shelf seas with specific criteria

step 4 : regional refinement (mesh-upgrade tool) for ocean ridges with specific criteria

step 5: mesh size control, iteration from step 3 if necessary

step 6: overall sanity and shape improvements (final mesh)

step 8: visual control and editing (xscan) if necessary

step 9: numbering optimisation (mesh-renum tool)

step 10: tidal simulation test

About 35 shelves/archipelago and 6 ocean ridge regions (defined in the *.plg files)  have been processed. The criteria file (*.crt) have been tuned to mitigate the necessary increase in resolution and the final mesh size. The construction is steered by a batch file to allow construction iterations.

FES2012 finite elements mesh

FES2012 mesh holds about 450 000 vertices, nearly twice more than FES2004 mesh. Hydrodynamic solutions are discretised on LGP2 nodes (~1 525 000 nodes) and discontinuous non-conforming P1 nodes (~2 300 000 nodes).