## K. Modal Analysis of a Closed Hydroelastic System (MOD5)

In this analysis, the structure and the fluid interact allalong their interface. The fluid domain must be closed, no radiating element being included in this model. The fluid surfaces not in contact with thestructure must then support zero pressure or zero flux conditions. Byrestricting the system of equations to the displacement and pressure fields,the following is obtained:

The code computes the eigenvalues and eigenvectors of thelinear system that are the eigenfrequencies and modes of the structure including the fluid domain. The computation is done using real values with nointernal losses.

The solid part can contain a piezoelectric ormagnetostrictive material only if valid boundary conditions are imposed. Thematrix equation is then more complicated than the equation above. The nonsymmetrical Lanczos' algorithm is used to solve the problem. The problem can be solvedonly in double precision.