探针操控下的声悬浮动力学特性
Dynamic characteristics of acoustic levitation under probe manipulation
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摘要: 以单轴式声悬浮和圆柱形探针为模型, 研究了探针沿水平方向进入和退出声场过程中球形悬浮样品的运动学特征和动力学机制。实验发现, 在一定距离范围内, 探针的靠近使悬浮样品振幅增大, 振动频率减小, 并对悬浮样品产生吸附效应。探针退出声场时的临界脱附距离大于其进入声场时的临界吸附距离, 表现出滞后效应。临界吸附距离和临界脱附距离均与探针直径成正比。有限元计算结果表明, 探针对悬浮样品产生吸附作用的机理是探针引起了声场的非轴对称分布, 产生了指向探针方向的声辐射力分量。计算结果还揭示了探针位置和直径对样品最大偏离距离和水平振动频率的影响规律, 与实验结果吻合。Abstract: Based on a protype that combines a single-axis acoustic levitator with a cylindrical probe, the kinematic and dynamic characteristics of an acoustically levitated spherical sample are studied when the probe enters and exits the sound field horizontally. The experiment shows that, within a certain distance, the approaching of the probe increases the vibration amplitude and reduces the vibration frequency of the levitated sample, and has an attraction effect on the sample. The critical detachment distance when the probe exits the sound field is larger than the critical attachment distance when it enters the sound field, showing a hysteresis effect. The critical attachment distance and the critical detachment distance are both proportional to the probe diameter. The finite element calculation reveals the mechanism of the attraction effect is the non-axisymmetric distribution of sound field induced by the probe, which produces a net component of acoustic radiation force directed towards the probe. The calculation also reveals the influence of probe position and diameter on the maximum offset distances of the sample and the frequency of horizontal vibration, which is consistent with the experimental results.