Translational and rotational resonance frequencies of a disk in a single-axis acoustic levitator

In this study, we investigate the acoustic levitation of a disk in a single-axis acoustic levitator operating at 21.53 kHz. First, two acoustic models based on the finite element method are employed for calculating the acoustic radiation force and torque on a levitating disk. The models are also used for calculating the vertical, horizontal, and torsional trapping stiffness and its corresponding natural frequencies. Furthermore, translational and angular oscillations of the disk are captured by a high-speed camera, and a tracking algorithm is employed for extracting the natural frequencies of the oscillations. The experimental natural frequencies present good agreement with those predicted by the models. Although the numerical model was employed for simulating the forces and torques on a disk, the presented method is general and it can be employed for simulating the acoustic levitation of objects of arbitrary shapes and sizes.