Mesh questions

[juan.e....@gmail.com]

Questions from github issue: https://github.com/devsim/devsim/issues/17#issuecomment-171147548

Sorry to bother you, but except transient, I have several questions about mesh I'd like to ask you.

On figure 3.1 in DevSim manual, I added n, p, Ψ and E, are they correct?

In your cap2d example, there are x-only and y-only mesh definitions independently each other.

create_2d_mesh(mesh=device)
add_2d_mesh_line(mesh=device, dir="y", pos=ymin, ps=0.1)
add_2d_mesh_line(mesh=device, dir="y", pos=y1 , ps=0.1)
add_2d_mesh_line(mesh=device, dir="y", pos=y2 , ps=0.1)
add_2d_mesh_line(mesh=device, dir="y", pos=y3 , ps=0.1)
add_2d_mesh_line(mesh=device, dir="y", pos=y4 , ps=0.1)
add_2d_mesh_line(mesh=device, dir="y", pos=ymax, ps=5.0)

device=device
region="air"

add_2d_mesh_line(mesh=device, dir="x", pos=xmin, ps=5)
add_2d_mesh_line(mesh=device, dir="x", pos=x1 , ps=2)
add_2d_mesh_line(mesh=device, dir="x", pos=x2 , ps=0.05)
add_2d_mesh_line(mesh=device, dir="x", pos=x3 , ps=0.05)
add_2d_mesh_line(mesh=device, dir="x", pos=x4 , ps=2)
add_2d_mesh_line(mesh=device, dir="x", pos=xmax, ps=5)

Does DevSim generates rectangular or triangle mesh? The plot by Paraview seems to show it is triangles.
Then, how can DevSim generate these triangles ?
And if triangles, what does node volume look like?

In your gmsh_diode3d example, I can see complicated triangle mesh not from rectangular mesh.
What is the policy of generating this mesh? And how? This may be impossible with DevSim functions.

[juan.e....@gmail.com]

Questions from github issue: https://github.com/devsim/devsim/issues/17#issuecomment-171147548

Sorry to bother you, but except transient, I have several questions about mesh I'd like to ask you.

On figure 3.1 in DevSim manual, I added n, p, Ψ and E, are they correct?

Edge models, such as electric field, are between 2 nodes.  Such a model is integrated with respect to the EdgeCouple as shown in Figure 3.2.  Please see section 3.2.2 of the manual for a description of how the ElectricField is formulated.  If you are considering the E field for the node in the center of your drawing, it should be reversed since it is the negative gradient of potential.
 

[juan.e....@gmail.com]

Questions from github issue: https://github.com/devsim/devsim/issues/17#issuecomment-171147548

In your cap2d example, there are x-only and y-only mesh definitions independently each other.

create_2d_mesh(mesh=device)
add_2d_mesh_line(mesh=device, dir="y", pos=ymin, ps=0.1)
add_2d_mesh_line(mesh=device, dir="y", pos=y1 , ps=0.1)
add_2d_mesh_line(mesh=device, dir="y", pos=y2 , ps=0.1)
add_2d_mesh_line(mesh=device, dir="y", pos=y3 , ps=0.1)
add_2d_mesh_line(mesh=device, dir="y", pos=y4 , ps=0.1)
add_2d_mesh_line(mesh=device, dir="y", pos=ymax, ps=5.0)

device=device
region="air"

add_2d_mesh_line(mesh=device, dir="x", pos=xmin, ps=5)
add_2d_mesh_line(mesh=device, dir="x", pos=x1 , ps=2)
add_2d_mesh_line(mesh=device, dir="x", pos=x2 , ps=0.05)
add_2d_mesh_line(mesh=device, dir="x", pos=x3 , ps=0.05)
add_2d_mesh_line(mesh=device, dir="x", pos=x4 , ps=2)
add_2d_mesh_line(mesh=device, dir="x", pos=xmax, ps=5)

Does DevSim generates rectangular or triangle mesh? The plot by Paraview seems to show it is triangles.
Then, how can DevSim generate these triangles ?
And if triangles, what does node volume look like?

DEVSIM considers triangular meshes in 2d and tetrahedral meshes in 3d.  The built in mesher in 2d creates a mesh with right triangles.  It generates the mesh from the specification with lines going straight through the mesh.  Then, the triangles are formed in the resulting rectangles.

The NodeVolume is formed from the perpendicular bisectors of the triangles in 2d.  A perpendicular line is drawn from the center of each line to the center of each triangle.  This is the EdgeCouple (from triangle center to triangle center) which forms the surface area of each node.  In 3d, a surface triangle is formed through the center of each Tetrahedron.

For the figures below, the perpendicular bisector of each diagonal edge would be 0.0 length.

 

The NodeVolume you propose here is incorrect.  Lines are formed perpendicular to each edge.

[juan.e....@gmail.com]

In your gmsh_diode3d example, I can see complicated triangle mesh not from rectangular mesh.
What is the policy of generating this mesh? And how? This may be impossible with DevSim functions.

DEVSIM only has simple meshers for 1D and 2D.  It is possible to import meshes generated from Gmsh, which is available here: 

http://gmsh.info/

For the gmsh_diode3d example, a mesh is imported from the .msh file generated in GMSH.  The mesh elements must be tetrahedra in 3d and triangles in 2d.

The original specification would be in a .geo file.  It looks like I did not include the .geo file for the diode in the DEVSIM project directories, but there are other .geo files such as:

./examples/bioapp1/disk_2d.geo

./examples/bioapp1/disk_3d.geo

./examples/mobility/gmsh_mos2d.geo

./examples/vectorpotential/twowire.geo

./testing/gmsh_mos2d.geo

./testing/gmsh_mos3d.geo

I may have a .geo file somewhere, which can recreate the diode structure.

[juan.e....@gmail.com]

It looks like there was a 2nd version of a figure that was created for these questions:

This figure is also incorrect.  It should actually look like this:

The NodeVolume is contained in the red box.  The flux is integrated through the perpendicular bisector of each edge.  For this special case, the length of the EdgeCouple for the diagonal lines is zero.