Identification of Method, Material & Boundary

The different elements of the model are specified using labels. Differents structures keep track of those labels:

  • elem.model(n) type of modelling for the n-th element
  • edge_msh(n,3) type of boundary for the n-th edge
  • elem.label(n) identifier for the material (can be set in the FreeFEM++ mesher)

Types of numerical models

Label Solving Method
1 FEM on TR6 (6 nodes triangles)
2 FEM on H12 (3 nodes triangles with Hermite splines interpolation)
3 FEM on TR3 (3 nodes triangles)
10 DGM on Triangles
11 DGM on Rectangles


The meshes between FEM and DGM can be incompatible.

Types of media

Label Media
0 Air
1XXX Elastic medium
2XXX Equivalent fluid (rigid frame) material
3XXX Limp model
4XXX Poroelastic Material (or FEM with 1998 formulation)
5XXX Biot (or FEM with 2001 formulation)
80xy PML (with x and y boolean direction)

Types of boundaries

Label Type of Boundary
1 Rigid wall
2 Unit pressure (fluid)
3 Unit normal velocity
4 Unit tangential velocity
5 Sliding (PEM)
6 Bonded (PEM) or clamped (elastic)
7 Unit pressure (PEM)
8 Unit normal velocity (PEM)
9 Unit tangential velocity (PEM)
10 Incident air plane wave on acoustic/Biot98 element
11 Incident air plane wave on elastic element
12 Incident air plane wave on Biot 2001 element
13 DtN plate (Dirichlet to Neumann)
20 Transmitted air plane wave on acoustic/Biot 98 element
21 Transmitted air plane wave on elastic element
21 Transmitted air plane wave on Biot 2001 element
60 Unit normal velocity on H12 with flux application
61 DGM radiative boundary
98 Periodicity left
99 Periodicity right
4xx ZOD even/odd
400 FSI (Fluid-Structure interaction)
1xyz Excitation wave 1 angle xyz in degree (PEM)
2xyz Excitation wave 2 angle xyz in degree (PEM)
3xyz Excitation wave 3 angle xyz in degree (PEM)
500 Velocity diffracion cylindre FEM