Nonlinear Phenomena Induced by Finite-Amplitude Oscillation of Air in Closed Tube : 3rd Report, Thermoacoustic Effects

The thermoacoustic effect is a nonlinear phenomenon produced by finite-amplitude oscillation of air in a closed tube. This effect generates a steady temperature distribution along the tube axis and causes heating and cooling of the tube wall at loop and node points of standing waves. Recently, the thermoacoustic effect has attracted the interest of many researchers, because it can be applied to the development of refrigerators that use a substitute for Freon. For practical design of the refrigerator and improvement of its efficiency, a detailed analysis of the thermoacoustic effect is required. Theoretically, the existence of the thermoacoustic effect has been analyzed by the perturbation method, and the results obtained in the case of small-amplitude oscillation agreed with the experimental results. However the experimental results in the case of finite-amplitude oscillation did not coincide with the theoretical results. This paper describes the numerical analysis of the thermoacoustic effect induced by finite-amplitude oscillation in an air-filled tube. The calculated results in the case of finite-amplitude oscillation with shock wave propagation show that the time-average of nonlinear term of the energy equation, which corresponds to steady heat flux, increases as the oscillation amplitude increases, and then the cooling effect vanishes