Abstract
This research describes the oscillatory flows inside and outside a thermoacoustic sound-wave generator. Two types of thermoacoustic sound-wave generators are employed. One is a conventional thermoacoustic sound-wave generator, 32 mm in inner diameter and either 860 mm or 1,133 mm long including the high- and low-temperature heat exchangers inside the resonance tube. The other is a simplified thermoacoustic sound-wave generator, 72 mm in inner diameter and 860 mm long, and has no heat exchangers inside the resonance tube. Simultaneous measurements of velocity and pressure were performed inside the resonance tube. Typical oscillatory flows, which include the Richardson effect near the tube wall, were observed inside the resonance tube of both types of sound-wave generator except immediately before the tube outlet. The differences between the inflow and outflow were ascertained near the tube outlet as well. Flow rates based on velocity amplitude are newly proposed for evaluating the flow singularities outside the resonance tube outlet. The forward flow rates, which increase up to 30 mm downstream from the tube outlet, decreased more than 30 mm downstream. On the other hand, the backward flow rates vanished more than 15 mm downstream. We also confirmed that the flow outside the resonance tube outlet changes from oscillatory flow at the tube outlet to pulsating flow far downstream.
