Study on Characteristics of Thermo-Acoustic Streaming

Thermo-acoustic streaming is a newly-found thermal convection. When heat is released locally in standing sound waves, it is generated toward a node. The driving force of this streaming is considered to be a kind of acoustic radiation force. To clarify the characteristics of this convection, the authors made visualization experiments and numerical simulations. Experiments were done in microgravity to remove the effects of buoyancy. In the simulations, FDTD (Finite Difference Time Domain method) and time-averaged model (ARF model) were used. The heat-source was placed at a node, an anti-node and the middle of the node and the anti-node. The node case, the simulations' results agree with experimental results well. The anti-node and the middle case, however, the ARF results do not agree with the others. Two-dimensional effect, i.e. a flow whose direction is perpendicular to the thermo-acoustic streaming is found. The Rayleigh streaming, the radiation force of 2-D standing sound waves and that of 2-D flow oscillating caused by local heating in the 1-D standing wave were examined as the causes of two-dimensional effect. Analyzing the FDTD, it is concluded that the cause of the flow is the result of the 2-D oscillating flow that occurs near the heat-source.