Faculty of Life and Medical Sciences, Doshisha University, 610-0321 Kyotanabe, Kyoto, Japan.
J Acoust Soc Am. 2011 Jul;130(1):135-44. doi: 10.1121/1.3592205.
The direction of the secondary Bjerknes force between a free bubble and an attached bubble was experimentally investigated. The behavior of the two bubbles in an ultrasonic standing wave of 27 kHz was observed using an imaging system with a high-speed video camera. It was demonstrated experimentally that the direction of the force reversed at a specific separation distance between the two bubbles, which was defined as the threshold distance. The threshold distance changed with the radius of the attached bubble. In addition, a theoretical calculation was performed using a previously derived model that coupled the vibrations of two free bubbles [Ida, Phys. Lett. A 297, 210-217 (2002)]. The experiment data for the threshold distance qualitatively agreed with the theoretical predictions, except when the separation distance was very small. Then, it was discovered that the free bubble became trapped near the attached bubble when the separation distance between the two bubbles was very small. This indicated that a stable equilibrium point for the separation distance exists that cannot be predicted by the theoretical model.
实验研究了自由气泡和附着气泡之间的次级 Bjerknes 力的方向。使用带有高速摄像机的成像系统观察了两个气泡在 27 kHz 超声驻波中的行为。实验证明，在两个气泡之间的特定分离距离处，力的方向发生了反转，该距离被定义为阈值距离。阈值距离随附着气泡的半径而变化。此外，使用先前推导的模型（该模型耦合了两个自由气泡的振动[Ida，Phys. Lett. A 297, 210-217 (2002)])进行了理论计算。除了分离距离非常小时，实验数据与理论预测定性一致。然后，发现当两个气泡之间的分离距离非常小时，自由气泡会被困在附着气泡附近。这表明存在一个无法通过理论模型预测的分离距离稳定平衡点。
