Multilayer modeling of thermoacoustic sound generation for thermophone analysis and design

Abstract

A general model for thermoacoustic sound generation, based on the classical conservation laws of mass, momentum and energy, is presented and adopted to analyze different thermophone structures. This model is able to describe an arbitrary multilayered (or laminated) system composed of both solid and fluid layers. In each layer, we consider the propagation of thermal and acoustic plane waves with a full thermo-visco-elastic coupling and with both thermal and viscous dissipations. In order to obtain a flexible model, useful for most of thermophone systems, the balance equations are written in a general and adaptable matrix form. By adding the continuity of temperature, particle velocity, normal stress and heat flux between the layers, we obtain a closed system of equations, which allows for the calculation of all the acoustic variables at any position and for any input frequency and power. The proposed technique is then applied to several thermophone architectures working in air or in water, and the results are discussed and compared to those of some recent theoretical and experimental investigations. Finally, the approach elaborated here is useful for unifying various theories proposed for distinct thermophone systems and to generalize these approaches in terms of different geometrical and physical features.