Transformation acoustics and applications to acoustic cloaking


The concept of transformation optics is to take a region of space and replace it with material occupying another region that has the same optical properties as the original. This opens up the possibility for cloaking: by replacing, e.g. a spherical region by a shell at its outer boundary it makes the interior invisible. The talk will discuss transformations that show these effects in acoustics and in elasticity. It will be shown that the acoustic material after transformation is not unique, unlike the case for electromagnetic waves. The non-uniqueness means that the same effects can be achieved using either anisotropic density or pentamode materials. Both of these unusual types of materials will be defined in detail in the talk, with the emphasis on pentamode materials (PM). Recent work on the design of PM-based devices will be described. This includes the concept of Metal Water which replaces water by an equivalent metal foam that has the acoustic wave speed and impedance of water, and low shear stiffness. By reshaping the material the empty spaces in the foam can be combined to give a large “cloaked” region. This type of material makes acoustic cloaking easy to understand, and potentially realizable. The Metal Water metamaterial also has interesting Bloch wave properties that have application for negative index of refraction devices, such as the superlens. The ideas of transformation optics do not work as nicely for elasticity. Some recent progress will be discussed.

讲座名称: Transformation acoustics and applications to acoustic cloaking

演讲人: Andrew Norris

所属学科: 法学

讲座关键字: 变换光学,声学隐形

讲座时间: 2013.09.06

  • 报告长度: 51 分钟
  • 播放次数: 10
  • 最大码流: 1500Kbps
  • 平均码流: 1500
  • 视频等级: 1
  • 文件类型: wmv

演讲人简介:Andrew Norris is an internationally recognized expert in modeling of acoustic and elastic wave phenomena. In his 30 year research career he has worked on topics ranging from ultrasonic nondestructive evaluation for detecting cracks in structures, modeling of underground sound for geophysical prospecting, to structural acoustics for naval applications. He is a Fellow of the Acoustical Society of America and of the Institute of Math. & Appl., editor in chief of the journal Wave Motion, and a member of the board of Editors of several journals including J. Acoustical Society of America, SIAM J. Applied Mathematics, and J. Elasticity. Awards received include: Fulbright Fellowship, Royal Society Fellowship, ASME Rayleigh Lecture 2011. He is currently a professor in the School of Engineering at Rutgers University in New Jersey.

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