This book is devoted to the study of coupled partial differential
equation models, which describe complex dynamical systems occurring in
modern scientific applications such as fluid/flow-structure
interactions. The first chapter provides a general description of a
fluid-structure interaction, which is formulated within a realistic
framework, where the structure subject to a frictional damping moves
within the fluid. The second chapter then offers a multifaceted
description, with often surprising results, of the case of the static
interface; a case that is argued in the literature to be a good model
for small, rapid oscillations of the structure. The third chapter
describes flow-structure interaction where the compressible
Navier-Stokes equations are replaced by the linearized Euler equation,
while the solid is taken as a nonlinear plate, which oscillates in the
surrounding gas flow. The final chapter focuses on a the equations of
nonlinear acoustics coupled with linear acoustics or elasticity, as they
arise in the context of high intensity ultrasound applications.