Fig. 2
From: Inducing drop to bubble transformation via resonance in ultrasound
Sound field and acoustic radiation pressure calculation. a Distribution of sound pressure field in levitator with no levitated sample. Distance between emitter and reflector D is 40.0 mm corresponding to the initiation of liquid film buckling and r is the cross-sectional radius of the reflector. Sound pressure level at the center of the emitter surface is 155.7 dB. Black cross denotes the sound pressure nodes of the sound field, i.e. possible levitation positions under zero gravity. Levitation positions under normal gravity are below the crosses. Dotted lines indicate curvatures of equipotential surfaces close to positions I and II. b and c Acoustic radiation pressure PA exerted on the liquid film surfaces (aqueous SDS drop, 10 μL) as a function of R* shown in inset: b flat liquid film, showing that PA is larger on the lower surface, c buckled liquid film, showing that PA on the upper surface becomes greater and is therefore responsible for the enhanced buckling
