Acoustic Levitation and the Acoustic Radiation Force
Student author: Ming-Hua Chang
American Journal of Physics
We investigate acoustic levitation in a vertical standing wave in an attempt to understand the basic physical mechanism responsible for this phenomenon. We find that a description in terms of a simple pressure force leads to the prediction of stable equilibria that occur slightly below the anti-nodes of the standing pressure wave. We then demonstrate that such a prediction is at odds with experimental data, which show that levitating particles come to rest slightly below the nodes of the standing pressure wave. Finally, we outline a theoretical approach based on fluid dynamics that correctly predicts the locations of the levitating particles, which leads to a simple qualitative description for this fascinating phenomenon.
Jackson, David P., and Ming-Hua Chang. "Acoustic Levitation and the Acoustic Radiation Force." American Journal of Physics 89, no. 4 (2021): 383-392. https://aapt.scitation.org/doi/full/10.1119/10.0002764