A two-frequency acoustic technique for bubble resonant oscillation studies

A two-frequency acoustic apparatus has been developed to study the dynamics of a single gas or vapor bubble in water. An advantage of the apparatus is its capability of trapping a bubble by an ultrasonic standing wave while i ndependently driving it into oscillations by a second lower frequency acous tic wave. For a preliminary application, the apparatus;is used to study res onant oscillations. First, near-resonant coupling between the volume and th e n = 3 shape oscillation modes of air bubbles at room temperature is studi ed, where n is the mode number. The stability boundary, amplitude versus fr equency, of the volume oscillation forms a wedge centered at the resonant f requency, which qualitatively agrees with a theoretical prediction based on a phase-space analysis. Next, the resonant volume oscillations of vapor bu bbles are studied. The resonant radius of vapor bubbles at 80 degrees C dri ven at 1682 Hz is determined to be 0.7 mm, in agreement with a prediction o btained by numerical simulation. (C) 2000 Acoustical Society of America. [S 0001-4966(00)03703-6].