MODE THEORY AS A FRAMEWORK FOR THE INVESTIGATION OF THE GENERATION OFA STONELEY WAVE AT A LIQUID-SOLID INTERFACE

A theoretical model, based on mode theory for acoustic waves, is prese nted in order to describe the complicated scattering of an ultrasonic volume or surface wave at the boundary between two adjacent liquids ab utting a single solid. Analytical expressions for the displacement fie lds of the scattered and mode-converted waves are derived. In particul ar, it is shown that a volume wave incident from the liquid of the fir st liquid/solid structure can generate a Stoneley wave along the inter face of the second liquid/solid structure. The relative amplitude of t he displacement of the excited Stoneley wave is calculated for several (liquid-liquid)/solid configurations. The angle of most efficient exc itation can be derived from the maximum of the function describing the interaction between a radiation mode and a Stoneley eigenmode in the division plane separating both liquid/solid structures.