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首页> 外文期刊>Physics of fluids >Acoustic streaming and thermal instability of flow generated by ultrasound in a cylindrical container
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Acoustic streaming and thermal instability of flow generated by ultrasound in a cylindrical container

机译：圆柱形容器中超声产生的声流和热不稳定性

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摘要

A vertically orientated ultrasonic transducer contained within a closed cylindrical Pyrex tube was used to study the acoustic streaming flow within a cylindrical container. A particle-image velocimetry (PIV) system incorporating fluorescent 1.5 mu m seeding particles suspended in a mixture of diethyl-phthalate and ethanol, whose optical index was matched to that of Pyrex, was used to allow for undistorted PIV imaging within the Pyrex tube. Temperature on the end-wall surface and acoustic pressure within the cylinder were measured for different end-wall materials. Variables considered included acoustic absorption and reflection coefficients, ultrasound intensity, container height, and thermal properties of the end-wall material. It was observed that a quasi-steady flow field driven by acoustic streaming is rapidly established within the container, which is typically dominated by a stationary vortex ring with downward flow along the ring axis. After sufficient time this quasi-stationary flow exhibits a thermal instability causing it to transform into a secondary flow state. Different types of secondary flow states were observed, including cases where the flow along the cylinder axis is oriented upward toward the ultrasound transducer and cases where the axial flow changes directions along the cylinder axis. Published by AIP Publishing.
机译：装在封闭的圆柱形派热克斯管中的垂直定向超声换能器用于研究圆柱形容器内的声流。粒子图像测速（PIV）系统采用荧光1.5微米接种粒子悬浮在邻苯二甲酸二乙酯和乙醇的混合物中，其光学指数与Pyrex的光学指数相匹配，用于在Pyrex管内进行无畸变的PIV成像。对于不同的端壁材料，测量了端壁表面的温度和圆柱体内的声压。考虑的变量包括吸声和反射系数，超声强度，容器高度和端壁材料的热性能。观察到，在容器内迅速建立了由声流驱动的准稳态流场，该流场通常由固定涡流环主导，该涡流环沿环轴线向下流动。经过足够的时间后，该准静态流表现出热不稳定性，导致其转变为二级流状态。观察到不同类型的次级流动状态，包括沿着圆柱轴的流动向上指向超声换能器的情况以及沿着圆柱轴的轴向流动改变方向的情况。由AIP Publishing发布。

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