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SUMMARY:Fast Boundary Element solvers in the frequency domain to simulate 
 coupled acoustic-elastic problems in the time domain. Application to the s
 imulation of underwater explosions - Stephanie Chaillat-Loseille (CNRS (Ce
 ntre national de la recherche scientifique))
DTSTART:20230421T100000Z
DTEND:20230421T104500Z
UID:TALK198766@talks.cam.ac.uk
DESCRIPTION:Assessing the impact of a remote underwater explosion on a sub
 merged structure (submarine) is an important naval engineering problem. An
  underwater explosion mainly induces two distinct phenomena: a &rdquo\;sho
 ck wave&rdquo\; followed by an oscillating bubble of gas. I will concentra
 te on the modeling of the shock wave in this talk.\n3D rapid transient aco
 ustic problems are known to be difficult to solve numerically when dealing
  with large geometries\, because numerical methods based on geometry discr
 etisation\, such as the BEM or the FEM\, often require to solve a linear s
 ystem (from the spacial discretisation) for each time step. In a first par
 t\, I will present&nbsp\; a numerical method to efficiently deal with 3D r
 apid transient acoustic problems set in large exterior domains. Using the 
 Z-transform and the convolution quadrature method (CQM)\, a straightforwar
 d way to reframe the problem to the solving of a large amount of frequency
 -domain BEMs is derived. Then\, taking advantage of a well-designed high-f
 requency approximation (HFA)\, the number of frequency-domain BEMs to be s
 olved is drastically reduced\, with little loss of accuracy. In a second p
 art\, I will discuss how to consider the FSI problem. A first approach&nbs
 p\; consists in iteratively solving the BEM-FEM coupling by alternating Ne
 umann solutions in each domain. Unfortunately this simple approach fails. 
 We can show that the transient BEM-FEM coupling based on Neumann-Neumann i
 terations is problematic since energy estimates indicate that each iterati
 on degrades the regularity of boundary traces (unlike in the elliptic case
 ). To avoid this issue\, an iterative algorithm based on Robin boundary co
 nditions for the coupled elastodynamic/acoustic problem will be presented 
 and proved to converge.\nThis is a join work with M. Bonnet\, A. Nassor an
 d D. Mavaleix-Marchessoux
LOCATION:Seminar Room 1\, Newton Institute
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