Measuring the void: Theoretical study of scattering by a cylindrical annulus

In this paper, we analyze a monochromatic plane wave scattering from an infinite homogeneous cylindrical annulus. In particular, we study the effect that the inner part of the cylindrical annulus (cylindrical void, if you will) has on the scattered field. This is done by isolating the cylindrical void's contribution to the scattered field. We show that if the cylindrical void is small, then its contribution to the scattered field may be approximated by the “screened cylindrical void” (SCV) approximation. We first develop the SCV approximation in a physically intuitive manner, and then show that it could also be obtained in a more mathematically rigorous manner. Numerical results comparing the SCV approximation to the exact solution are also presented.

► The effect that the inner part of a cylindrical annulus (cylindrical void) has on the scattered field is analyzed. ► The cylindrical void's contribution to the scattered field is approximated by the “screened cylindrical void” (SCV) approximation. ► The SCV approximation is developed in a physically intuitive manner. ► The SCV approximation is developed in a mathematically rigorous manner. ► Numerical results show that the SCV approximation is in good agreement with the exact solution.