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SUMMARY:Willis couplings in one-dimensional and quasi-one-dimensional acou
 stic systems - Jean-Philippe Groby (CNRS (Centre national de la recherche 
 scientifique))
DTSTART:20230413T123000Z
DTEND:20230413T140000Z
UID:TALK199258@talks.cam.ac.uk
DESCRIPTION:Since the seminal work of Willis in the 80&rsquo\;s\, the epon
 ymous materials have received an increasing attention\, because of their a
 nalogy with bi-anisotropic electromagnetic metamaterials. The Willis coupl
 ing parameters couple the potential and kinetic energy in the acoustic con
 servation relations\, therefore enhancing the ability to control waves in 
 metamaterials compared to other materials that do not exhibit such couplin
 g. In this talk\, I will present a general method to derive the closed for
 m expressions of the effective properties\, including the Willis coupling\
 , of asymmetric and nonreciprocal one dimensional acoustic systems. This m
 ethod relies on the Pade&rsquo\;s approximation of the matrix exponential\
 , the latter being nothing but the transfer matrix that may relate the sta
 te vectors at both sides of a unit cell. The effective properties of vario
 us one-dimensional asymmetric resonant systems are first derived\, numeric
 ally and experimentally validated\, and analyzed. The nonlocal feature of 
 the Willis coupling is then investigated in a simple fluid laminate system
 . The asymmetric and nonreciprocal Willis couplings are finally analytical
 ly derived and discussed in a system constituted of a periodic arrangement
  of thermoacoustic amplifiers. \nCo-authors:&nbsp\;M. Mall&eacute\;jac\, T
 . Cavalieri\, C. Olivier\, G. Poignand\, V. Tournat\, V. Romero-Garc&iacut
 e\;a\, Guillaume Penelet\, A. Merkel\, D. Torrent\, J. Li\, and J. Christe
 nsen\n&nbsp\;\n&nbsp\;
LOCATION:Seminar Room 2\, Newton Institute
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