Finite Element Analysis of the Standing Wave Field in a Tube with Lossy Wall for Thermoacoustic System

Abstract

The finite element method (FEM) is applied to the analysis of the steady-state sound field in a thermoacoustic tube in the frequency domain. Although the thermoacoustic field is nonlinear and isothermal, a linear and adiabatic model is proposed, in which only the sound intensity field is considered because the sound intensity is generally discussed for the efficiency of energy conversion in the thermoacoustic system. In the numerical model, the divergence of the sound intensity is modeled as the sound source and the dissipation is modeled as loss caused by the specific acoustic impedance of the wall. Some numerical demonstrations are made for the two-dimensional standing wave field in a straight tube with a lossy wall. The influences of the stack and the phase adjuster on the sound field are examined. It is found that the sound field in the thermoacoustic tube can be qualitatively analyzed by introducing the specific acoustic impedance of the wall.