Numerical UTD diffraction coefficients with hybrid topologic method

When one is interested in the scattering cross section of large bodies, asymptotic techniques such as UTD are numerically efficient. In practice the set of shapes which may be addressed with such methods is restricted since the usual (analytical) diffraction coefficients are limited to canonical shapes. However, in a large number of engineering problems, small complex inhomogeneous bulges and cavities may exist in the vicinity of the surface of the large body and their influence on the diffracted field often has to be taken into account. We show how it is possible to define rigorously numerical diffraction coefficients for these small bodies through the use of the hybrid topologic method.