Stability Analysis of Coupled Structural Acoustics PDE Models under Thermal Effects and with no Additional Dissipation

In this study we consider a coupled system of partial differential equations (PDE's) which describes a certain structural acoustics interaction. One component of this PDE system is a wave equation, which serves to model the interior acoustic wave medium within a given three dimensional chamber $% \Omega $. This acoustic wave equation is coupled on a boundary interface ($% \Gamma _{0}$) to a two dimensional system of thermoelasticity: this thermoelastic PDE comprises a structural beam or plate equation, which governs the vibrations of flexible wall portion $\Gamma _{0}$ of the chamber $\Omega $; the elastic dynamics is coupled to a heat equation which also evolves on $\Gamma _{0}$, and which imparts a thermal damping onto the entire structural acoustic system. As we said, the interaction between the wave and thermoelastic PDE components takes place on the boundary interface $% \Gamma _{0}$, and involves coupling boundary terms which are above the level of finite energy. We analyze the stability properties of this coupled structural acoustics PDE model, in the absence of \ any additive feedback dissipation on the hard walls $\Gamma _{1}$ of the boundary $\partial \Omega $. Under a certain geometric assumption on $\Gamma _{1}$, an assumption which has appeared in the literature in conection with structural acoustic flow, and which allows for the invocation of a recently derived microlocal boundary trace estimate, we show that classical solutions of this thermally damped structural acoustics PDE decay uniformly to zero, with a rational rate of decay.