The 2D programs can model two types of geometry:
1. Two Dimensional (2D)
This mode is used when the real geometry is long enough in one direction that a contour plot of relevant physical properties (voltage, fields, etc.) would lie on a plane. This is illustrated below.
In this case, the 2D program works with a planar cross-section of the geometry.
2. Rotational Symmetric (RS) – aka “Axisymmetry” or “Azimuthal Symmetry”
This mode is used when the real geometry could be created by sweeping a cross section of the geometry around a central axis. This is illustrated below.
In this mode, the 2D program works with the planar cross-section w hich would be rotated to create the true geometry.
Note that while 2D mode is always an approximation based on ignoring end effects, if a geometry is truly RS, then the RS mode provides the full 3D answer.