Adjustable Orientation for Right Circular Cylinder

spraguep · March 27, 2025, 7:12pm

Hello,

I’ve come across the need to make cylinders that are not parallel to the x, y, or z axis. I’ve seen a few threads about using quadric surfaces and cell rotations (see Model angular Cylinder sarfaces), but I think it would be very helpful to add an option to the openmc.model.RightCircularCylinder class to either define a unit vector for the cylinder axis, while keeping the ability to define with just ‘x’, ‘y’, or ‘z’ (to prevent existing code from breaking) or change the class to be similar to the new openmc.model.ConicalFrustum class (openmc.model.ConicalFrustum — OpenMC Documentation) where the composite surface is defined by two vectors: the center_base (x0, y0, z0) and the axis (dx, dy, dz), similar to the RCC macrobody in MCNP (see image below).

Any thoughts?

paulromano · March 27, 2025, 7:32pm

Agreed, it would be nice to have this option directly. In the meantime, you can look at the conversion logic in our MCNP to OpenMC converter for how this can be done using the existing functionality:

github.com/openmc-dev/openmc_mcnp_adapter

src/openmc_mcnp_adapter/openmc_conversion.py

a3714a9cd


      
          # Create vectors for Z-axis and cylinder orientation
          u = np.array([0., 0., 1.])
          h = np.array([hx, hy, hz])
          
          # Determine rotation matrix to transform u -> h
          rotation = rotation_matrix(u, h)
          
          # Create RCC aligned with Z-axis
          height = np.linalg.norm(h)
          surf = RCC((vx, vy, vz), height, r, axis='z')
          
          # Rotate the RCC
          surf = surf.rotate(rotation, pivot=(vx, vy, vz))

Topic		Replies	Views
Model angular Cylinder sarfaces User Support	3	220	February 28, 2019
OpenMC Quadric surfaces in different position in Z axis. User Support	3	219	July 9, 2019
Example of a Quadric surface. User Support	3	420	March 6, 2019
Rotating cylinder User Support	3	261	September 30, 2017
Problem model.cylinder_from_points User Support	2	401	May 5, 2022

Adjustable Orientation for Right Circular Cylinder

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