Generation of jumping of planar objects and breath-like jet flow generated by high-intensity sound pressure formed near vibrating surface

Interesting nonlinear phenomena caused by the high-intensity sound pressure formed near the vibrating surface have been revealed. As novel object manipulation by nonlinear acoustics, the jumping phenomenon of a levitated object and the air jet flow phenomenon similar to breathing are presented. Near-field acoustic levitation (NFAL) occurs when a planar object is placed on a flat vibrating surface. However, for NFAL above the vibrating surface with a recess, a phenomenon was observed in which the levitated object jumped up when the vibration amplitude increased. The jumping phenomenon was understood to be caused by the sound pressure resonance in the cavity between the levitated object and the vibrating surface by increasing the levitation distance. A jet flow phenomenon similar to breathing was observed from a small hole when the object with the hole was placed close to the vibrating surface. Particle image velocimetry confirmed that the air did not flow through the air gap and the hole. The flow velocity of the jet changed to the object's thickness, the vibration amplitude, and the air gap between the object and the vibrating surface. The mechanism, applications to manipulation, and current research on these phenomena are described.