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![Effect of wedge truncation length x 0 on the reflection coefficient R 0 : solid curve corresponds to an uncovered wedge, dashed, dotted and dashdotted curves correspond to a wedge covered by absorbing films with the values of E 2 /E 1 equal to 0.1, 0.2 and 0.3; the film material loss factor ν is 0.15, and the film thickness δ is 15 µm [2]](profile/Victor-Krylov/publication/282160675/figure/fig4/AS:668307803889678@1536348405947/Effect-of-wedge-truncation-length-x-0-on-the-reflection-coefficient-R-0-solid-curve.png)
Effect of wedge truncation length x 0 on the reflection coefficient R 0 : solid curve corresponds to an uncovered wedge, dashed, dotted and dashdotted curves correspond to a wedge covered by absorbing films with the values of E 2 /E 1 equal to 0.1, 0.2 and 0.3; the film material loss factor ν is 0.15, and the film thickness δ is 15 µm [2]
Source publication
'Acoustic black holes' are relatively new physical objects that have been introduced and investigated mainly during the last decade. They can absorb almost 100% of the incident wave energy, which makes them attractive for such traditional engineering applications as vibration damping and sound absorption. They could be useful also for some ultrason...
Contexts in source publication
Context 1
... effect of wedge truncation length x 0 on the reflection coefficient R 0 in the above example is shown in Fig. 2. For comparison, the curve corresponding to the wedge not covered by absorbing layers is shown as well. One can see that the behaviour of the reflection coefficient R 0 as a function of x 0 is strongly influenced by the absorbing layers. In particular, the effect of absorbing layers results in drastic reduction of the reflection ...
Context 2
... addition to the above-mentioned two types of acoustic black holes for sound absorption in air, we consider here a new interesting possibility of creating acoustic black holes for absorption of sound propagating in liquid-filled flexible pipes with walls of variable thickness (Fig. ...
Context 3
... c 0 is the sound velocity in open liquid, β 0 is the compressibility of the liquid, a is the internal radius of the pipe, δ is the thickness of its flexible walls, E and ν are the Young's modulus and the Poisson's ratio of the pipe material respectively (see Fig. 12). Fig. 12. Geometry of a liquid-filled pipe with flexible walls of variable ...
Context 4
... c 0 is the sound velocity in open liquid, β 0 is the compressibility of the liquid, a is the internal radius of the pipe, δ is the thickness of its flexible walls, E and ν are the Young's modulus and the Poisson's ratio of the pipe material respectively (see Fig. 12). Fig. 12. Geometry of a liquid-filled pipe with flexible walls of variable ...
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Citations
... However, ideal ABHs cannot be constructed and the wedges must be truncated at some point. This brings adverse effects on the performance of the ABHs [10]. Even if the cut-off thickness is minimal (which is hard to manufacture in practice, see e.g. ...
To obtain a well-damped structure, the concept of “acoustic black hole (ABH)” is proposed to trap bending waves at the edge of the wedge shape. However, in the current practice, the remarkable effect of intrinsic lengths is not incorporated. This study aims to reveal the remarkable contribution due to the interplay between intrinsic and extrinsic lengths, which is of fundamental scientific interest. The nonlocal theory is employed to examine the dynamical behaviors of the ABH incorporating the effect of intrinsic lengths. The theoretical model is established for microstructure-dependent power-law plates, and the solution method is developed for analyzing the reflection coefficient of microstructure-dependent power-law plates and bars. It is found that the effect of the microstructure-dependent nonlocality becomes significant and the ABH shows a better absorption of acoustic energy when the nonlocal intrinsic length tends to be lager. Furthermore, the reflection coefficient of traditional works is underestimated. Also, the relationship between the reflection coefficient and wedge truncation length, and frequency is discussed in detail.
We use a recently developed class of metamaterials based on geometric inhomogeneities to design acoustic lenses embedded in thin-walled structural element. The geometric inhomogeneity is based on the concept of Acoustic Black Hole (ABH) that is an exponential taper fully integrated in the supporting structure. The ABH is an element able to bend and, eventually, trap acoustic waves by creating areas with carefully engineered phase velocity gradients. Periodic lattices of ABHs are first studied in terms of their dispersion characteristics and then embedded in thin-plate structures to create lenses for ultrasonic focusing and collimation. Numerical simulations show the ability of the ABH lens to create focusing and collimation effects in an extended operating range that goes from the metamaterial to the phononic regime.
