Ultrasonic leaky guided waves in fluid-coupled generic waveguides: hybrid finite-boundary element dispersion analysis and experimental validation

A numerical procedure is presented for the computation of dispersive parameters in elastic mechanical waveguides of generic cross-section immersed in non-viscous fluids. The method uses a semi-analytical finite element formulation to describe the solid waveguide, while a two and- a-half dimensional boundary element method is used to represent the unbounded surrounding fluid. Leaky and trapped guided wave modes are found on the appropriate Riemann sheets by enforcing the generalized Snell–Descartes law along the fluid-structure interface and solving a nonlinear eigenvalue problem. The method is validated experimentally by extracting the frequency-real wavenumber dispersion curves of a rectangular bar and a thin angle aluminum bar via a two-dimensional Fast Fourier Transform. In both cases, a very good agreement is observed between the numerical and the experimental solutions.