Acoustic metafluids

Norris, Andrew N.

doi:10.1121/1.3050288

Cited by 195 publications

(118 citation statements)

References 16 publications

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“…The anisotropic densities needed to realize such cloaks could be achieved by using layered fluids [112,113] (see also [114,115]), however, Norris [17] realized that such inertial cloaks suffer from a considerable mass penalty. He presented an alternative route to designing cloaks for acoustic waves based upon pentamode materials [17,116,117].…”

Section: Coordinate Transformations and Metamaterialsmentioning

confidence: 99%

Elastic metamaterials and dynamic homogenization: a review

Srivastava

2015

International Journal of Smart and Nano Materials

122

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In this paper, we review the recent advances which have taken place in the understanding and applications of acoustic/elastic metamaterials. Metamaterials are artificially created composite materials which exhibit unusual properties that are not found in nature. We begin with presenting arguments from discrete systems which support the case for the existence of unusual material properties such as tensorial and/or negative density. The arguments are then extended to elastic continuums through coherent averaging principles. The resulting coupled and nonlocal homogenized relations, called the Willis relations, are presented as the natural description of inhomogeneous elastodynamics. They are specialized to Bloch waves propagating in periodic composites and we show that the Willis properties display the unusual behavior which is often required in metamaterial applications such as the Veselago lens. We finally present the recent advances in the area of transformation elastodynamics, charting its inspirations from transformation optics, clarifying its particular challenges, and identifying its connection with the constitutive relations of the Willis and the Cosserat types.

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Section: Coordinate Transformations and Metamaterialsmentioning

confidence: 99%

Elastic metamaterials and dynamic homogenization: a review

Srivastava

2015

International Journal of Smart and Nano Materials

122

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“…Though there are many theoretical studies and proposals of cloaking devices based on transformation acoustics [4,[9][10][11]] only a few experimental results have been reported so far [12]. More recently, the research on cloaking has been extended to flexural waves, where also reduced cloaks have been proposed [13] and experimentally reported [14].…”

Section: Introductionmentioning

confidence: 99%

Broadband Acoustic Cloaking within an Arbitrary Hard Cavity

et al. 2015

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This paper reports the design, fabrication, and experimental validation of a broadband acoustic cloak for the concealing of three-dimensional (3D) objects placed inside an open cavity with arbitrary surfaces. This 3D cavity cloak represents the acoustic analogue of a magician hat, giving the illusion that a cavity with an object is empty. Transformation acoustics is employed to design this cavity cloak, whose parameters represent an anisotropic acoustic metamaterial. A practical realization is made of 14 perforated layers fabricated by drilling subwavelength holes on 1-mm-thick Plexiglas plates. In both simulation and experimental results, concealing of the reference object by the device is shown for airborne sound with wavelengths between 10 cm and 17 cm.

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“…One of the most important applications of this technique is the cloaking of acoustic waves. [7][8][9][10][11][12] One possible problem in this process is that the transformations from physical to virtual space may result in metamaterials that cannot be realized in practice. In order to overcome this problem, several authors [13,14] have proposed to invert the process by first studying the range of realizable material parameters, and then deriving the appropriate transformations which guarantee the desirable effect, such as acoustic cloaking.…”

Section: Introductionmentioning

confidence: 99%

Space–time transformation acoustics

et al. 2014

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A recently proposed analogue transformation method has allowed the extension of transformation acoustics to general spacetime transformations. We analyze here in detail the differences between this new analogue transformation acoustics (ATA) method and the standard one (STA). We show explicitly that STA is not suitable for transformations that mix space and time. ATA takes as starting point the acoustic equation for the velocity potential, instead of that for the pressure as in STA. This velocity-potential equation by itself already allows for some transformations mixing space and time, but not all of them. We explicitly obtain the entire set of transformations that leave its form invariant. It is for the rest of transformations that ATA shows its true potential, allowing for building a transformation acoustics method that enables the full range of spacetime transformations. We provide an example of an important transformation which cannot be achieved with STA. Using this transformation, we design and simulate an acoustic frequency converter via the ATA approach. Furthermore, in those cases in which one can apply both the STA and ATA approaches, we study the different transformational properties of the corresponding physical quantities.

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Acoustic metafluids

Cited by 195 publications

References 16 publications

Elastic metamaterials and dynamic homogenization: a review

Elastic metamaterials and dynamic homogenization: a review

Broadband Acoustic Cloaking within an Arbitrary Hard Cavity

Space–time transformation acoustics

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