The history force on bubbles translational motion in an acoustic field.

In this study, the translational trajectory of bubble in an ultrasonic standing wave at 22.4 kHz was observed using an imaging system with a high-speed video camera. This allowed the velocities of bubble be measured when the acoustic pressure at 20 kPa, 40 kPa and 60 kPa, which applied to indirectly measured the history force by using the acoustic and hydrodynamic forces balance model. It shown that bubbles driven at low acoustic pressure, the history force close to zero, and with the pressure increase the history force change to large, the ratio of F/F from 0.33 at 40 kPa to 1.73 at 60 kPa, the result is different with prior research when the Reynolds numbers is large, and useful in the understanding of bubble moments in an acoustic field.