Experimental investigation of acoustic streaming flows inside a standing wave tube

Acoustic streaming is identified as one of the several phenomena which affect the efficiency of thermoacoustic system by causing convective heat transfer. In the context of thermoacoustic machines, most of the experimental and numerical studies were performed on Rayleigh acoustic streaming. In the present study, different acoustic streaming flows within a standing wave tube were investigated. Experiments were performed using particle image velocimetry. A rectangular Plexiglas resonator was used as an idealized standing wave thermoacoustic refrigerator. The experimental results were compared with linear acoustic theory to ascertain their validity. Acoustic streaming generated due to interaction of standing wave with thermoacoustic core was also studied. Simplified components were used to model the stack and heat exchangers. It was found that presence of rigid obstacles in the standing wave resonator changed the streaming flow completely. Both the magnitude and shape of the streaming cells changed when compared with the classical Rayleigh streaming cell. The resulting local streaming velocity due to rigid obstacles in the standing wave tube had very high magnitude when compared with streaming in an empty standing wave tube.