Absorbing Boundaries and Finite Elements for Transient and Harmonic SteadyState Acoustic FluidStructure Interaction.
Abstract
This thesis is concerned with the development, validation, implementation and application of an efficient finite elementbased methodology to the modeling and solution of acoustic fluidstructure interaction problems that spatially involve infinite or semiinfinite regions and temporally span either the transient or the harmonic steadystate regimes. The primary objective is the development of a simple, robust and accurate methodology that will make the acoustic fluidstructure interaction problem amenable to standard and widely available solution techniques and therefore will also allow for the easy incorporation of the proposed methodology into existing engineering analysis software tools. This work favors a unified variational approach for tackling the coupling between the acoustic fluid and the structure, and absorbing boundaries for dealing with the infinite or semiinfinite fluid domain, while using finite elements as the numerical approximations. The theoretical development includes a systematic procedure for the construction, in two and three dimensions, of a family of stable artificial boundary conditions of increasing complexity and accuracy for general convex geometries, and the formulation of the fluidstructure interaction problem for wave propagation in either an infinite or semiinfinite region in terms of symmetric operators. A central component of the theoretical development involves the casting of secondorder absorbing boundary conditions, within the context of a finite element formulation, as a set of local infinite elements located at the boundary of the computational domain, with each element defined by a pair of symmetric, timeinvariant, stiffness and damping matrices. This makes it possible to readily incorporate the new infinite element into finite element software developed for purely interior regions, for applications involving steadystate harmonic or transient excitations. The proposed methodology is applied to a variety of problems including rigid and elastic scattering problems involving canonical and arbitrary geometries in two and threedimensions, both in the frequency and the timedomains.
 Publication:

Ph.D. Thesis
 Pub Date:
 January 1995
 Bibcode:
 1995PhDT........54K
 Keywords:

 Engineering: Civil; Physics: Acoustics; Applied Mechanics