Axial PML Performance Near the Axis of Rotation in Cylindrical FDTD

This work investigates the effect of proximity to the axis of rotation on the perfectly-matched-layer (PML) absorbing boundary condition when used to truncate cylindrical finite-difference time-domain (FDTD) simulations along the axial dimension. The investigation is based on deriving predictive equations for the overall reflection coefficient off the innermost PML interface which rely heavily on a recently derived numerical dispersion relation for cylindrical FDTD. Accounting for cylindrical waves behavior near the axis of rotation is critical in realizing appropriate cylindrical FDTD and PML performance near the axis of rotation.