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SUMMARY:Weak localization in radiative transfer of acoustic waves in rando
 mly-fluctuating half-space\, slab\, and box. - Régis Cottereau (CNRS (Cen
 tre national de la recherche scientifique))
DTSTART:20230324T133000Z
DTEND:20230324T140000Z
UID:TALK195748@talks.cam.ac.uk
DESCRIPTION:\n\n\nThis presentation first discusses the derivation of radi
 ative transfer equations for acoustic waves propagating in a randomly fluc
 tuating half-space in the weak-scattering regime\, and the study of bounda
 ry effects through an asymptotic analysis of the Wigner transform of the w
 ave solution. These radiative transfer equations allow to model the transp
 ort of wave energy density\, taking into account the scattering by random 
 heterogeneities. The approach builds on the method of images\, where the h
 alf-space problem is extended to a full-space\, with two symmetric sources
  and an even map of mechanical properties. Two contributions to the total 
 energy density are then identified: one similar to the energy density prop
 agation in a full-space\, for which the resulting lack of statistical stat
 ionarity of the medium properties has no leading-order effect\; and one su
 pported within one wavelength of the boundary\, which describes interferen
 ce effects between the waves produced by the two symmetric sources. In the
  case of a homogeneous Neumann boundary conditions\, this boundary effect 
 yields a doubling of the intensity\, and in the case of homogeneous Dirich
 let boundary conditions\, a canceling of that intensity. In a second part 
 of the presentation\, these results will be extended to the case of a rand
 omly-fluctuating slab (layer of material bounded by two parallel planes) a
 nd of a randomly-fluctuating box. The extension of the method of images to
  slabs requires the consideration of models fluctuating periodically at th
 e large scale\, but this has no first-order influence on the results obtai
 ned for the half space. Radiative transfer simulations (using a Monte-Carl
 o approach) will be presented to illustrate the results.\nThis is a joint 
 work with Adel Messaoudi and Christophe Gomez. The first part of the prese
 ntation can be read at https://hal.science/hal-03878927/document.\n\n\n
LOCATION:Seminar Room 1\, Newton Institute
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