Revolve a 2-D profile into a 3-D solid CSG?

User Support
1

Hi all,

I’m building a model in OpenMC using CSG. What I’d like to do is:

  1. Sketch a 2-D cross-section of a nuclear reactor (the lines are all parabolic),
  2. Revolve that profile 360° about a central axis (say the z-axis),
  3. End up with the corresponding 3-D volume, within the CSG system.

I haven’t found a “revolve”/“sweep” command in the docs. Before I start piecing the shape together, I wanted to check:

  1. Does OpenMC-CSG have a built-in way to revolve a surface/curve into a solid?
  2. If not, what’s the usual workaround - approximating with analytic surfaces, importing a CAD model through DAGMC, or something else?

Thanks in advance! :slight_smile:

2

Hi Ozzy,

As far as I am aware there is not built in method to revolve a parabolic curve around an axis, but there are methods to approximate it. You have a few options depending on what results you’re looking for, the first option, which is best computationally would be to do only a 2d slice with quadric surfaces as your reactor is symmetrical around the axis. The other method would be to approximate the curve with repeated stacked cylinders. A code that could be used for this is below,

a = 5.0 # controls curvature
y_max = 100.0
n_layers = 100

Reactor_Shell = []
for i in range(n_layers):
    z0 = i * y_max / n_layers
    z1 = (i + 1) * y_max / n_layers
    r0 = np.sqrt(a * z0)
    r1 = np.sqrt(a * z1)

    cyl_inner = openmc.ZCylinder(r=r0)
    cyl_outer = openmc.ZCylinder(r=r1)
    surf_bottom = openmc.ZPlane(z0=z0)
    surf_top = openmc.ZPlane(z0=z1)

    cell = openmc.Cell(region=-cyl_outer & +cyl_inner & +surf_bottom & -surf_top, fill=Reactor_material)
    Reactor_shell.append(cell)

    r_max = np.sqrt(a * y_max)

This is using the following equation to define the paraboloid
x2+z2=ay
with “a” being a constant. This equation can be adjusted for your specific curvature.

You could also import from a CAD software if you’re more familiar with that, though I don’t have any experience with that process. Let me know if you have any other questions.