More Like this

1. Modeling and identification of electro-elastic nonlinearities in ultrasonic power transfer systems

   https://doi.org/10.1007/s11071-019-04959-x  

   Meesala, Vamsi C.; Hajj, Muhammad R.; Shahab, Shima (January 2019, Nonlinear Dynamics)

   We establish a nonlinear nonconservative mathematical framework for the acoustic-electro-elastic dynamics of the response of a piezoelectric disk to high-level acoustic excitation in the context of ultrasound acoustic energy transfer. Nonlinear parameter identification is performed to estimate the parameters representing nonlinear piezoelectric coefficients. The identification is based on exploiting the vibrational response of the disk operating in the thickness mode under dynamic actuation. The nonlinearly coupled electro-elastic governing equations, for the piezoelectric receiver subjected to acoustic excitation, are derived using the generalized Hamilton's principle. The method of multiple scales is used to obtain an approximate solution that forms the basis for parameter identification. The identified coefficients are then experimentally validated. The effects of varying these coefficients on the nonlinear response, optimal resistive electrical loading, and power generation characteristics of the receiver are investigated. 

   more » « less
2. Investigating Spectral Distortion of Local Volcano Infrasound by Nonlinear Propagation at Sakurajima Volcano, Japan

   https://doi.org/10.1029/2019JB018284  

   Maher, Sean P.; Matoza, Robin S.; de Groot‐Hedlin, Catherine D.; Gee, Kent L.; Fee, David; Yokoo, Akihiko (March 2020, Journal of Geophysical Research: Solid Earth)

   Abstract Sound waves generated by erupting volcanoes can be used to infer important source dynamics, yet acoustic source‐time functions may be distorted during propagation, even at local recording distances (15 km). The resulting uncertainty in source estimates can be reduced by improving constraints on propagation effects. We aim to quantify potential distortions caused by wave steepening during nonlinear propagation, with the aim of improving the accuracy of volcano‐acoustic source predictions. We hypothesize that wave steepening causes spectral energy transfer away from the dominant source frequency. To test this, we apply a previously developed single‐point, frequency domain, quadspectral density‐based nonlinearity indicator to 30 acoustic signals from Vulcanian explosion events at Sakurajima Volcano, Japan, in an 8‐day data set collected by five infrasound stations in 2013 with 2.3‐ to 6.2‐km range. We model these results with a 2‐D axisymmetric finite‐difference method that includes rigid topography, wind, and nonlinear propagation. Simulation results with flat ground indicate that wave steepening causes up to2 dB (1% of source level) of cumulative upward spectral energy transfer for Sakurajima amplitudes. Correction for nonlinear propagation may therefore provide a valuable second‐order improvement in accuracy for source parameter estimates. However, simulations with wind and topography introduce variations in the indicator spectra on order of a few decibels. Nonrandom phase relationships generated during propagation or at the source may be misinterpreted as nonlinear spectral energy transfer. The nonlinearity indicator is therefore best suited to small source‐receiver distances (e.g.,2 km) and volcanoes with simple sources (e.g., gas‐rich strombolian explosions) and topography. 

   more » « less
3. Characterization of nonlinear electro-elastic behavior of piezoelectric receiver in ultrasound acoustic energy transfer systems

   Meesala, Vamsi; Hajj, Muhammad; Shahab, Shima (January 2019, NODYCON 2019 Springer Proceedings)

   A scheme based on the approximate solution determined by the method of multiple scales is proposed for the identification of nonlinear material parameters of a piezoelectric disc. The theoretical approach is experimentally validated to determine these parameters through dynamic electrical actuation. The identified material parameters are then used to investigate the nonlinear electro-elastic behavior of the disk, used as a receiver, in an ultrasound acoustic energy transfer system. 

   more » « less
4. Evidence for near-source nonlinear propagation of volcano infrasound from Strombolian explosions at Yasur Volcano, Vanuatu

   https://doi.org/10.1007/s00445-022-01552-w  

   Maher, Sean P.; Matoza, Robin S.; Jolly, Arthur; de Groot-Hedlin, Catherine; Gee, Kent L.; Fee, David; Iezzi, Alexandra M. (March 2022, Bulletin of Volcanology)

   Abstract Volcanic eruption source parameters may be estimated from acoustic pressure recordings dominant at infrasonic frequencies (< 20 Hz), yet uncertainties may be high due in part to poorly understood propagation dynamics. Linear acoustic propagation of volcano infrasound is commonly assumed, but nonlinear processes such as wave steepening may distort waveforms and obscure the sourcing process in recorded waveforms. Here we use a previously developed frequency-domain nonlinearity indicator to quantify spectral changes due to nonlinear propagation primarily in 80 signals from explosions at Yasur Volcano, Vanuatu. We find evidence for$$\le$$ $\le$10⁻³ dB/m spectral energy transfer in the band 3–9 Hz for signals with amplitude on the order of several hundred Pa at 200–400 m range. The clarity of the nonlinear spectral signature increases with waveform amplitude, suggesting stronger nonlinear changes for greater source pressures. We observe similar results in application to synthetics generated through finite-difference wavefield simulations of nonlinear propagation, although limitations of the model complicate direct comparison to the observations. Our results provide quantitative evidence for nonlinear propagation that confirms previous interpretations made on the basis of qualitative observations of asymmetric waveforms. 

   more » « less
5. Wave redirection, localization, and non-reciprocity in a dissipative nonlinear lattice by macroscopic Landau–Zener tunneling: Experimental results

   https://doi.org/10.1063/5.0047806  

   Kanj, A.; Wang, C.; Mojahed, A.; Vakakis, A.; Tawfick, S. (June 2021, AIP Advances)

   Nonlinear lattices and the nonlinear acoustics they support have a broad impact on shock and vibration mitigation, sound isolation, and acoustic logic devices. In this work, we experimentally study wave redirection, localization, and non-reciprocity in an asymmetric network of two nonlinear lattices with weak linear inter-lattice coupling. We report on the design, fabrication, and system identification of coupled lattices with essentially nonlinear next-neighbor intra-lattice coupling and on their unusual nonlinear acoustics. By weakly coupling the lattices and introducing structural disorder in one of them, we experimentally prove the realization of irreversible breather redirection between lattices governed by a macroscopic analog of the quantum Landau–Zener tunneling effect. In the experiments performed, the input energy is applied by impulse (broadband) excitation, and the resulting acoustical mechanism for wave redirection is in the form of propagating breathers, that is, localized oscillating wave packets formed by the synergy of nonlinearity and dispersion. Moreover, we study the non-reciprocal acoustics of the experimental lattice system by applying separate impulses at each of its four terminals and investigate the tunability with the energy of the resulting acoustic non-reciprocity by systematically varying the impulse intensity. The reported experimental results show that the weakly coupled, disordered, and nonlinear lattice system has wave tailoring properties that are tunable with energy. Altogether, the experimental results agree well with theoretical predictions reported in a companion work based on reduced-order numerical models and prove the efficacy of the system for applications, providing a path for applying these advanced concepts in future structures and devices. 

   more » « less