A Metamaterial Acoustic Concentrator With Regular Polygonal Cross Section

Abstract

The phenomenon of near-field concentration of sound wave plays an important role in harnessing of sound wave in underwater sonar or similar devices, where high pressure field is required. Material parameters for the metamaterial-assisted acoustic concentrators with arbitrary N-sided regular polygonal cross section are derived based on coordination transformation approach. Acoustic intensity enhancement of the concentrator has been shown by full-wave simulation. All theoretical and numerical results validate the generality and effectiveness of the proposed designing method.

Arbitrary Shaped Acoustic Concentrators Enabled by Null Media

“…As can be seen from Fig.5, different shape concentrators are achieved without changing the materials of Eq. (6) and their results exhibit strong agreement with their previous counterparts which were achieved by performing tedious calculations [12][13][14][15].…”

“…However, to the authors' best knowledge, most of the previous works were limited to the cylindrical-cross section concentrators which limit their performances for being used in more general cases where there is a prerequisite to focus acoustic intensity in an arbitrary region of interest. Although Yang et al [15] performed some theoretical investigations for this aim, the propounded approach cannot be utilized in realistic situations since its obtained materials are geometry dependent. That is by changing the geometry of the transformed medium, one must recalculate its necessitating materials, which is a tedious and sophisticated procedure especially when the geometry of the preferable media is irregular.…”

Inverse design based metamaterial concentrator and its applications and realization

“…Since the cylindrical concentrator was first proposed by Rahm et al [16], many further investigations on the concentrator have been conducted, including non-rotationally invariant concentrator [17], cone-shaped concentrator [18], arbitrary shaped concentrators [19], homogeneous-materials-constructed concentrator [20,21], concentrator with only axial parameter spatially variant [22], and concentrator with minimized scattering [23]. Moreover, the scope of the research has been gradually extended from optics to acoustics [24], plasmonics [25], elastodynamics [26] and even thermodynamics [27]. The foregoing investigations are really attractive, but it should be pointed out that the design method for all the aforementioned concentrators share a common feature that in order to derive the material parameters of the device, the transformation function between the original space and the transformed space must be known in advance.…”

Homogeneous material based acoustic concentrators and rotators with linear coordinate transformation

“…It wasn't long before it was introduced into acoustics. In 2011, Yang designed an acoustic concentrator 20 based on coordinate transformation. In 2014, Jiang designed the inhomogeneous acoustic rotator 21 .…”