This paper explores the concept of an acoustic black hole (ABH) as a main design framework for performing dynamic structural tailoring of mechanical systems for vibration energy harvesting applications. The ABH is an integral feature embedded in the host structure that allows for a smooth reduction of the phase velocity, theoretically approaching zero, while minimizing the reflected energy. This mechanism results in structural areas with high energy density that can be effectively exploited to develop enhanced vibration-based energy harvesting. Fully coupled electro-mechanical models of an ABH tapered structure with surface mounted piezo-transducers are developed to numerically simulate the response of the system to both steady state and transient excitations. The design performances are numerically evaluated using structural intensity data as well as the instantaneous voltage/power and energy output produced by the piezo-transducer network. Results show that the dynamically tailored structural design enables a drastic increase in the harvested energy as compared to traditional structures, both under steady state and transient excitation conditions.

https://iopscience.iop.org/article/10.1088/0964-1726/23/6/065021/pdf

Broadband energy harvesting using acoustic black hole structural tailoring

https://hal.archives-ouvertes.fr/hal-02519297/document

The acoustic black hole: A review of theory and applications

Characterization of acoustic black hole effect using a one-dimensional fully-coupled and wavelet-decomposed semi-analytical model

The concept of an Acoustic Black Hole (ABH) has been developed and exploited as an approach for passively attenuating structural vibration. The basic principle of the ABH relies on proper tailoring of the structure geometrical properties in order to produce a gradual reduction of the flexural wave speed, theoretically approaching zero. For practical systems the idealized “zero” wave speed condition cannot be achieved so the structural areas of low wave speed are treated with surface damping layers to allow the ABH to approach the idealized dissipation level. In this work, an investigation was conducted to assess the effects that distributions of ABHs embedded in plate-like structures have on both vibration and structure radiated sound, focusing on characterizing and improving low frequency performance. Finite Element and Boundary Element models were used to assess the vibration response and radiated sound power performance of several plate configurations, comparing baseline uniform plates with embedded periodic ABH designs. The computed modal loss factors showed the importance of the ABH unit cell low order modes in the overall vibration reduction effectiveness of the embedded ABH plates at low frequencies where the free plate bending wavelengths are longer than the scale of the ABH.

Numerical analysis of the vibroacoustic properties of plates with embedded grids of acoustic black holes.

The Acoustic Black Hole (ABH) effect can be used to effectively reduce structural vibrations by trapping flexural waves in a thin-walled structure with a power-law thickness variation In the present study, we used a wavelet-decomposed energy method to investigate an Euler-Bernoulli beam embedded with multiple ABHs Broadband transmission attenuation bands at relatively low frequencies are observed in a beam containing only a few ABH elements To explain the underlying phenomena, an infinite structure with periodic ABH elements is analyzed Numerical results show that the periodic boundary conditions in terms of displacement and rotational slope of a unit cell, based on the finite model, are sufficient to describe the band structures, without requiring full treatment of the entire infinite structure This provides an efficient and flexible means to predict, and eventually optimize, the band structure based on a single element Meanwhile, the ABH-induced locally resonant band gaps coincide with the attenua

/pdf/broadband-locally-resonant-band-gaps-in-periodic-beam-1ncsyed3ci.pdf

E.P. Bowyer

Papers

Experimental investigation of damping flexural vibrations in plates containing tapered indentations of power-law profile

Experimental investigation of damping flexural vibrations in glass fibre composite plates containing one- and two-dimensional acoustic black holes

Effect of geometrical and material imperfections on damping flexural vibrations in plates with attached wedges of power law profile

Experimental study of sound radiation by plates containing circular indentations of power-law profile

Damping of flexural vibrations in turbofan blades using the acoustic black hole effect