A numerical method for modeling ultrasonic guided waves in thin-walled waveguides coupled to fluids

•Thin-walled waveguides in contact with fluids support complex guided wave modes.•Coupling FEM and BEM at mid-surfaces simplifies meshing procedure.•Fluid-loading can lead to non-dispersive L modes over broad frequency ranges.•Mode coupling effects can determine spikes of attenuation values. The pap...

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Bibliographic Details
Published in:Computers & structures 2019-02, Vol.212, p.248-256
Main Authors: Mazzotti, M., Miniaci, M., Bartoli, I.
Format: Article
Language:English
Subjects:
Attenuation
Boundary element
Boundary element method
Computational fluid dynamics
Deformation effects
Eigenvalues
Finite element method
Fluid-loaded waveguides
Mathematical analysis
Mathematical models
Nonlinear programming
Numerical analysis
Numerical methods
Rectangular waveguides
SAFE
Shear deformation
Thin-walled structures
Ultrasonic testing
Viscoelasticity
Wave propagation
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Summary:•Thin-walled waveguides in contact with fluids support complex guided wave modes.•Coupling FEM and BEM at mid-surfaces simplifies meshing procedure.•Fluid-loading can lead to non-dispersive L modes over broad frequency ranges.•Mode coupling effects can determine spikes of attenuation values. The paper presents a hybrid numerical method for the computation of the dispersion characteristics of ultrasonic guided waves propagating in isotropic and viscoelastic thin-walled waveguides in contact with fluids along their inner or outer wall. To this end, the solid waveguide is modeled by means of a Semi-Analytical Finite Element method implementing the first order shear deformation theory, while the effects of the fluid are taken into account by means of a regularized 2.5D Boundary Element Method with Helmholtz-type kernels. By coupling the two methods along the mid-surface of the solid waveguide, the dispersion relations of the elastic-acoustic system are obtained as the solution of a nonlinear eigenvalue problem in the complex axial wavenumbers for any fixed circular frequency. Two different case studies are presented: an oil-filled pipe and a water-loaded steel rectangular waveguide.
ISSN:0045-7949
1879-2243
DOI:10.1016/j.compstruc.2018.11.002