## 4pUW11. Scattering from an axisymmetric structure insonified at any incidence using a coupled finite-element/boundary element method.

### Session: Thursday Afternoon, December 5

### Time: 3:49

**Author: Antoine Lavie**

**Location: Institut d'Electronique et de Microelectronique du Nord, U.M.R. C.N.R.S. 9929, Departement I.S.E.N., Lab. d'Acoustique, 41 Boulevard Vauban, 59046 Lille Cedex, France**

**Author: Bertrand Dubus**

**Location: Institut d'Electronique et de Microelectronique du Nord, U.M.R. C.N.R.S. 9929, Departement I.S.E.N., Lab. d'Acoustique, 41 Boulevard Vauban, 59046 Lille Cedex, France**

**Abstract:**

In the field of the scattering of acoustic waves from structures immersed
in an infinite fluid medium, a coupling between the EQI boundary element code
and the ATILA finite-element code is available. The boundary element method used
is the Helmholtz integral equation. At some frequencies, called irregular
frequencies, this integral formulation presents an infinite number of solutions.
This problem is solved with the help of the Jones method: The integral equations
system is overdetermined by null-field equations. Many structures are
axisymmetric. So, it is attractive to develop a modeling that is able to keep
the advantages of the axis of symmetry and to take into account an incident wave
of any direction. This numerical tool is performed using a harmonic cylindrical
decomposition. In this case, the mesh is restricted to the line of the structure
included in the meridian plane. Compared with three-dimensional modeling, this
new possibility provides the following advantages: either a reduction of the
computation time, the memory size, and the disk storage space and an improvement
of the numerical behavior; or an increase of the maximum frequency. Comparison
between numerical results and experimental data is presented.

ASA 132nd meeting - Hawaii, December 1996