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Guided modes admissible in elastic hollow pipes are derived to establish their dispersion and attenuation characteristics in the presence of multi-layered viscoelastic coatings. Longitudinal waves propagating in the axial direction in response to displacement continuity boundary conditions signifying perfect interfacial bonds are evaluated against a baseline uncoated tubing. Viscoelastic bitumen and epoxy are coating materials applied to improve pipeline reliability. The impact of viscoelastic coating layers on wave dispersion and attenuation are investigated by incorporating complex material properties in the characteristic equation. The real and complex roots of the corresponding characteristic equation are determined, allowing the phase velocity and attenuation dispersion to be depicted as functions of the propagation frequency. The effects of varying attenuation parameter and coating thickness are also examined. Viscoelastic protective materials are found to have a substantial impact on the propagation and attenuation of longitudinal waveguide modes.

Numerical analysis of wave propagation in composite structures needs large-scale computation which is not feasible in practice. This paper investigates the possibility of applying a wave finite element method (WFEM) to composite structure. The key feature of the WFEM is its capability of accurately analyzing the discontinuities in stress wavefront along with the discontinuities in velocities and strains. In addition, the numerical analysis of the WFEM is unconditionally stable and reduces numerical computation. This paper studies a periodically layered composite rod to analyze the dispersion and propagation of stress waves using the WFEM. The numerical results are compared with other numerical/analytical solutions, paying attention to the accuracy of computing the strong discontinuities in the stress wavefront as well as the dispersion of pulses in a heterogeneous elastic rod. It is shown that the WFEM can be used as an affordable tool for numerically solving wave propagation in composite structures.

On January 1, 2024, a moment magnitude (Mw) 7.5 earthquake struck the Noto Peninsula area in Japan, triggering a tsunami and causing significant casualties and massive economic and property damage. Many wave gauges around the Sea of Japan recorded the tsunami. In this study we inverted the observed tsunami waveforms for the distributed slip on the JSPJ (Japan Sea Earthquake and Tsunami Research Project) fault model, and the initial water elevation, respectively. The results show that the earthquake’s slip distribution concentrates mainly on the NT4 subfault located to the northeast of the peninsula, with the maximum slip reaching about 5m. This slip model results in a maximum initial tsunami wave height that reaches ∼3m. The inversion of initial water elevation indicates a main tsunami source roughly located in $137.3^{\circ }$E$-137.6^{\circ }$E and $37.5^{\circ }$N$-37.8^{\circ }$N, with the maximum initial elevation of 2.7m, which is consistent with the finite-fault inversion. We also simulated the tsunami waveforms at observation stations using the inverted JSPJ fault model and the initial water elevation to evaluate the effects of wave dispersion. The results indicate that the effects of dispersion were minor at most stations, and only observable at far-field stations along the eastern Russian coast and the western coast of Hokkaido.

Numerical studies are conducted to investigate the existence of wave dispersion in resonant column tests on dry granular soil. The distinct element method (DEM) in the time domain is employed in two and three-dimensions to simulate the laboratory apparatus. The investigations focus on the effect of sample width, voids ratio. viscous damping and wavelength, on propagation velocities of longitudinal harmonic waves in rectangular samples consisting of uniform grains. It is shown that granular materials may exhibit anomalous dispersion that is, wave velocities that increase with increasing excitation frequency. This increase may be significant for squatty samples, yet becomes less pronounced for slender samples. The dispersion effects tend to be more pronounced in 2D over 3D analyses which suggests waveguide dispersion. Similar findings have been reported in some experiments on granular materials, but have not been systematically explored by numerical means. Results are presented in the form of dimensionless graphs and charts that elucidate the salient features of the problem.