BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//talks.cam.ac.uk//v3//EN
BEGIN:VTIMEZONE
TZID:Europe/London
BEGIN:DAYLIGHT
TZOFFSETFROM:+0000
TZOFFSETTO:+0100
TZNAME:BST
DTSTART:19700329T010000
RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=-1SU
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:+0100
TZOFFSETTO:+0000
TZNAME:GMT
DTSTART:19701025T020000
RRULE:FREQ=YEARLY;BYMONTH=10;BYDAY=-1SU
END:STANDARD
END:VTIMEZONE
BEGIN:VEVENT
CATEGORIES:Isaac Newton Institute Seminar Series
SUMMARY:Coherent elastic waves in multiple scattering medi
a: influence of resonances and positional correlat
ions of scatterers - Tony Valier-Brasier (Sorbonne
Université)
DTSTART;TZID=Europe/London:20230427T160000
DTEND;TZID=Europe/London:20230427T170000
UID:TALK199261AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/199261
DESCRIPTION:The propagation of elastic waves in heterogeneous
media is a fundamental research topic that concern
s composite materials\, porous materials\, colloid
s and emulsions\, with the aim of characterising t
hese materials or optimising their performance. Th
is subject has benefited from renewed interest wit
h the development in the 2000s of metamaterials an
d in particular locally resonant metamaterials. Th
ese materials consist of a fluid or solid matrix c
ontaining an ordered or random distribution of sca
tterers\, whose resonances alter wave propagation.
In some cases\, the macroscopic mechanical proper
ties of these materials are modified in non-ordina
ry ways\, opening the way to wave control or dampi
ng. Other strategies have been implemented to cont
rol or guide waves\, such as phononic crystals or
topological metamaterials. Recently\, the control
of spatial correlations in random scatterer distri
butions has emerged as a new approach\, and in par
ticular the use of hyperuniform distributions has
proven to be particularly relevant.\nIn this conte
xt\, the objective of the presented work is to stu
dy the influence of positional correlations betwee
n scatterers and strong sub-wavelength resonances
on the propagation of coherent elastic waves. To a
chieve this\, the work is based on the systematic
comparison of results from statistical models\, nu
merical simulations and experiments. The numerical
results are obtained using the MuScat calculation
code\, developed in the laboratory. This code is
based on the resolution of the multiple scattering
equations as well as on the development of the in
cident and scattered fields on the cylindrical or
spherical harmonics. It allows the treatment of va
rious wave interaction problems with many scattere
rs\, without any restriction on the distribution o
f the particles\, nor on their polydispersity in s
ize or elasticity.\nThe MuScat code is used to stu
dy the influence of positional correlations betwee
n scatterers on coherent waves. Two types of corre
lation are investigated: short-range correlations\
, which are based simply on an exclusion distance
between each pair of scatterers\, and long-range c
orrelations\, which apply to the whole distributio
n. One type of material that exhibits these long-r
ange correlations is hyperuniform media\, which ar
e characterised by the cancellation of density flu
ctuations as the volume of the medium tends toward
s infinity. Numerical simulations highlight the el
astic wave transparency regime of hyperuniform med
ia\, as well as the existence of complete stop ban
ds. Short-range correlations\, which are much simp
ler to implement\, lead to similar results.\nIn a
second step\, we investigate the propagation of co
herent elastic waves in a distribution of dense be
ads embedded in a softer solid matrix. This partic
le-matrix pair exhibits two sub-wavelength dipolar
resonances: a translational resonance that affect
s both longitudinal and transverse waves and a rot
ational resonance that affects only transverse wav
es. Longitudinal coherent waves are then strongly
influenced by the translational resonance and the
study of statistical models shows that wave conver
sions are particularly important. Transverse coher
ent waves are influenced by translational and rota
tional dipole resonances\, and increasing concentr
ation leads to the simultaneous propagation of two
coherent waves. The influence of spatial correlat
ions\, especially short-range correlations\, final
ly allows to optimise these non-ordinary effects.
LOCATION:Seminar Room 2\, Newton Institute
CONTACT:
END:VEVENT
END:VCALENDAR