Diffraction of plane waves having complex frequency and the excitation of transient leaky Rayleigh waves

Abstract

Harmonic plane waves are not advantageous for stimulation of leaky Rayleigh waves whereas bounded beams are better suited. Furthermore, past studies have revealed that it is even better to apply incident harmonic inhomogeneous waves, both on smooth and on rough surfaces. If the right inhomogeneity is used, very strong excitation is to be expected. However, inhomogeneous waves are difficult to generate and are far from practical outside the laboratory boundaries. The current paper describes how incident harmonic plane waves having a complex frequency are also excellent tools for stimulating leaky Rayleigh waves, if the technique is combined with the use of a periodically rough surface. Such transient plane waves are much more practical to generate experimentally whence the usability of the technique is more realistic compared with the classical use of harmonic inhomogeneous waves. [Work supported by The Flemish Institute for the Encouragement of the Scientific and Technological Research in Industry (I.W.T.).]