Scattering, transformation acoustics and non-reciprocal wave propagation

Tuesday, March 14, 2017 - 2:00pm - 2:50pm
Keller 3-180
Andrew Norris (Rutgers, The State University of New Jersey)
First, I will discuss a now-classic topic but with some new twists: Transformation acoustics (TA), focusing on the special case of isotropic TA for which the required properties can be realized by a wide variety of homogenized structures. First, the ability of conformal mappings to yield highly accurate focusing lenses is described. These act via reciprocity as monopole to highly one-way-wave radiators. Second, matching to the exterior fluid places constraints on the TA map that are explored. Examples will be described that are optimally matched in both impedance and focusing. Example realization of devices using pentamode materials will be described.

The talk will review some recent work on spatiotemporally modulated materials, also known as Dynamic Materials (Lurie, 2007), which exhibit non-reciprocal wave effects. It is shown that a modulated phononic crystal can be described by Willis equations with coupling terms related to the non-reciprocity. Some recent results for modulation of a metamaterial will be discussed.