dolfin team mailing list archive

[Catherine Micek <mice0012@xxxxxxx>]

Hi,

I am working on a 3D finite element code and would like to use a  
cylinder mesh.  Since there is no built-in cylinder mesh, I tried  
generating one from a the built-in UnitCube mesh:

# Create mesh
mesh = UnitCube(2,2,2)

# Translate origin from (0.5, 0.5, 0.5) to (0.0, 0.0)
for x in mesh.coordinates():
        x[0] = x[0] - 0.5
        x[1] = x[1] - 0.5
        x[2] = 4.0*(x[2] - 0.5)

# Create boundary mesh
boundary = BoundaryMesh(mesh)

# Stretch to a circle
for x in boundary.coordinates():
        # Circle parameters
        theta = atan2(x[1],x[0])
        r = 2.0
        x[0] = r*cos(theta)
        x[1] = r*sin(theta)
        x[2] = x[2]

# Move boundary values of mesh
mesh.move(boundary)

The mesh plots in Viper fine and looks nice, but does not work  
properly when I use it in code.  When I look at the .xml file, some  
identical vertices are numbered twice, as though they are being  
interpreted as different vertices.  I'm not sure what's causing this,  
although it seems to be related to the dimension: when I run similar  
code on the UnitSquare in 2D to generate a circle, I don't encounter  
this problem

So my questions are these:

1. Is there a way to correct this code so that the mesh can be  
generated without repeated vertices?
2. I have Matlab code to generate a cylinder; is there an easy way to  
convert that to a form that can be used by fenics?

Any suggestions would be greatly appreciated -- thanks!

Katy

---
Catherine (Katy) A. Micek
Graduate Assistant, U of MN Mathematics Department
http://www.math.umn.edu/~mice0012