Mesh refinement along intersections

[dthillaithevan]

Hi,

I'm trying to generate a 3D mesh which is composed of two cylinders of different radii stacked on top of each other. I would like to refine the mesh along the circle at their intersection (where the arrow is shown here).

I've tried to adapt the examples shown in the docs but haven't had much luck so far, do you have any tips for how I can proceed with this?

with pygmsh.occ.Geometry() as geom:
    geom.characteristic_length_max = 0.02

    cylinders = [
        geom.add_cylinder([0.0, 0.0, 0.0], [0.0, 1, 0.0], 0.1),
        geom.add_cylinder([0.0, 1, 0.0], [0.0, 0.5, 0.0], 0.2),
    ]
    geom.boolean_union(cylinders)
    
    # refine mesh around the intersection of the two cylinders
    # (𝑥)**2+(𝑦)2+(𝑧)**2=𝑟**2 where y = 1   
    
    # Code below causes this error: TypeError: <lambda>() takes 5 positional arguments but 6 were given
    # geom.set_mesh_size_callback(
    #         lambda dim, tag, x, y, z: (((x**2 + y**2 + z**2)))
    #     )
    
    
    # Or could use something like this work? I couldn't find any way to add a full circle
    # circ = geom.add_circle(
    #     add circle defined along intersection of cylinders
    # )

    # field0 = geom.add_boundary_layer(
    #     edges_list=[circ.curves[0]],
    #     ........
    # )

    mesh = geom.generate_mesh()

Thanks in advance!