Experimental study of acoustic turbulence and streaming in a thermoacoustic stack

Recent developments in thermoacoustic devices have generated a renewed interest in finite amplitude standing waves and the nonlinear effects associated with them. In a typical thermoacoustic device, a stack and two heat exchangers are placed inside a resonator approximately midway between the velocity and pressure antinodes. These elements, consisting of closely spaced rigid plates, present both a discontinuity in the fluid flow and a rigid boundary with which the fluid can interact. Under these conditions, at least two well‐known effects may occur: acoustic streaming and turbulence. These effects are of particular interest since they could significantly affect the thermoacoustic heat transport inside the stack. In this study, the fluid velocity inside and near a stack was measured qualitatively and quantitatively using a stroboscopic lamp and a laser Doppler velocimeter, respectively. Measurements under different conditions will be presented and discussed. [Work supported by ONR.]