Control, observation and polynomial decay for a coupled heat-wave system

This Note is devoted to study the control, observation and polynomial decay of a linearized 1-d model for fluid-structure interaction, where a wave and a heat equation evolve in two bounded intervals, with natural transmission conditions at the point of inter-face. These conditions couple, in particular, the heat unknown with the velocity of the wave solution. The controllability and observability of the system through the wave component are derived from sidewise energy estimate and Carleman inequalities. As for the control and observation through the heat component, we need to develop first a careful spectral high frequency analysis for the underlying semigroup, which yields a new Ingahm-type inequality. It is shown that the controllable/observable subspace for both cases are quite different. Also, we obtain a sharp polynomial decay rate for the energy of smooth solutions. (C) 2003 Academie des sciences. Published by Editions scientifiques et medicales Elsevier SAS. All rights reserved.