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Source publication
Phononic crystals are well known for acoustic wave manipulation which may have potential application in an underwater acoustic detection system. In this work, we design and simulate a two-dimensional Luneburg lens based on gradient-index (GRIN) phononic crystal that is composed of PLA-Air inclusion, and a novel application of GRIN phononic crystals...
Citations
... Nejad [33] created an acoustic fiber with a higher refractive index than uniform air using cross-shaped phononic crystals. Ruan [34] and Ahmed Allam [35] constructed 2D and 3D phononic crystal focusing lenses based on the equivalent gradient refractive index feature possessed by gradient phononic crystals for applications in underwater acoustic focusing. ...
In this work, a phononic crystal gradient metamaterial structure (PCGMs) is proposed based on the strong wave compression effect coupled with equivalent medium theory to achieve enhancement and directional sensing of weak target acoustic signals. Compared with the conventional gradient structure, PCGMs exhibit superior acoustic enhancement performance and wider range of acoustic response capability. Numerical analysis and experimental validation consistently demonstrate that PCGMs can effectively enhance the target frequency signals in harmonic signals. This study breaks through the detection limit of acoustic sensing systems and provides a great method for engineering applications of weak acoustic signal perception.
... It is much easier to achieve required refractive index to design the ALL in air due to the large impedance differences between the air and lens. However, it is much more complicated to design ALL in water due to the relatively small impedance differences between the lens and water [66,67]. Allam et al. [50] introduced an efficient and simple design method for ALL, whose unit cells were composed of elastic matrix with air inclusions. ...
Acoustic Luneburg lens (ALL) is a spherically/circularly symmetric gradient refractive index lens, whose index varies smoothly from the outer surface to the centre. The variation of the index can be achieved via the changing of filling ratio of unit cells or varying the structural thickness based on specific governing equations. The fundamental principles were used to explain the acoustic wave propagation in such inhomogeneous media, and to design different types of ALL. This review will describe the fundamental theories of ALL, introduce different types of ALL, and discuss extensive applications of ALL, which have been exploited for the manipulation and control of both acoustic and elastic waves.
... The properties of subwavelength phonon crystal (PC) arrays provide ideas for solving this problem. PC arrays can be constructed with the characteristics of high refractive index media [35][36][37]. Therefore, in this work, a device made from axisymmetric three-dimensional gradient metamaterials which incorporate phononic crystals (GAM-PC) is proposed, which has a gradient profile, a gradient plate thickness, and a gradient gap width along the axis of the wave propagation direction. ...
Conventional acoustic systems exhibit a difficulty in sensing weak acoustic fault signals in complex mechanical vibration environments. Therefore, it is necessary to develop an acoustic sensing mode and a corresponding functional device with pressure amplification. This paper proposes a three-dimensional device, coupling gradient acoustic metamaterials (GAM) with phononic crystals (GAM–PC). The strong wave compression effect coupled with the phononic crystal equivalent medium mechanism is utilized to achieve the enhancement of weak acoustic signal perception at the target frequency. The superior amplification capability of the GAM–PC structure for the amplitude of loud signals is verified by numerical simulations and experiments. Moreover, the GAM–PC structure has a narrower bandwidth per slit, making it more frequency selective. Furthermore, the structure can separate different frequency components. This work is expected to be applied to signal monitoring in environments with strong noise.
... 在材料无损检测领域, 人工结构透镜能够用于 提升检测材料中缺陷、裂纹和异物的分辨率, 以及材 料厚度测量、黏结强度测试、金属材料硬度精准度测 试等 [4,5] . 此外, 在水下通讯领域, 可利用人工结构透镜 产生衍射抑制或涡旋声束进行水下信号远距离传输, 实现水下定位和信息传递等应用 [6,7] . . 自2011年以来, 哈 佛大学Yu等人 [11] [11,25,26] , 通过合理设计透镜单胞的相位 调制参数, 可实现入射平面波在任意点聚焦. ...
... It is much easier to achieve required refractive index to design the ALL in air due to the large impedance differences between the air and lens. However, it is much more complicated to design ALL in water due to the relatively small impedance differences between the lens and water [66,67]. Allam et al. [50] introduced an efficient and simple design method for ALL, whose unit cells were composed of elastic matrix with air inclusions. ...
Purpose
Acoustic signals of the underwater targets are susceptible to noise, reverberation, submarine topography and biology, therefore it is difficult to precisely locate underwater targets. This paper proposes a new underwater Hanbury Brown-Twiss (HBT) interference passive localization method. This study aims to achieve precise location of the underwater acoustic targets.
Design/methodology/approach
The principle of HBT interference with ultrasensitive detection characteristics in optical measurements was introduced in the field of hydroacoustics. The coherence of the underwater target signal was analyzed using the HBT interference measurement principle, and the corresponding relationship between the signal coherence and target position was obtained. Consequently, an HBT interference localization model was established, and its validity was verified through simulations and experiments.
Findings
The effects of different array structures on the localization performance were obtained by simulation analysis, and the simulations confirmed that the HBT method exhibited a higher positioning accuracy than conventional beamforming. In addition, the experimental analysis demonstrated the excellent positioning performance of the HBT method, which verified the feasibility of the proposed method.
Originality/value
This study provides a new method for the passive localization of underwater targets, which may be widely used in the field of oceanic explorations.
