Bjerknes forces between two bubbles. Part 2. Response to an oscillatory pressure field
Bjerknes forces between two bubbles. Part 2. Response to an oscillatory pressure field
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DOI：
10.1017/s002211209300223x
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发表时间：
1993-09
影响因子：
3.7
通讯作者：
N. Pelekasis;J. Tsamopoulos
中科院分区：
文献类型：
--
作者：
N. Pelekasis;J. Tsamopoulos
本文研究了两个气泡在环境压力振荡扰动下的运动。结果表明，大小不等的气泡的相对运动依赖于扰动的频率。如果该频率在单个气泡的体积振荡的两个固有频率之间，则可以看到两个气泡彼此远离;否则吸引力占主导地位。相同大小的气泡只能相互吸引，而与振荡频率无关。当Bond数Bo（基于平均加速度）位于临界区域以上时，出现球帽形状，变形限制在气泡背向加速度方向的一侧。对于低于临界区域的Bo，由于亚谐共振，发生跨越整个气泡表面的形状振荡。振荡声场的存在为系统增加了一个频率，并增加了共振的可能性。然而，仅观察到亚谐波共振，因为它发生在更快的时间尺度O（1/ε）上，其中ε是扰动幅度。此外，在每个气泡的体积的不同可能的周期变化，具有较小的周期决定哪勒让德模式将通过亚谐共振激发。球帽形状也发生在时间尺度O（1/ε）上。当气泡被驱动到低于共振并且对于相当大的声压振幅ε <$0.8时，获得了体积振荡的固有频率的一半处的次谐波信号。该信号主要与第零模式相关联，并且对应于体积膨胀，随后是气泡的快速崩溃，这是声空化实验中有充分记录的行为。
The motion of two gas bubbles in response to an oscillatory disturbance in the ambient pressure is studied. It is shown that the relative motion of bubbles of unequal size depends on the frequency of the disturbance. If this frequency is between the two natural frequencies for volume oscillations of the individual bubbles, the two bubbles are seen to move away from each other; otherwise attractive forces prevail. Bubbles of equal size can only attract each other, irrespective of the oscillation frequency. When the Bond number, Bo (based on the average acceleration) lies above a critical region, spherical-cap shapes appear with deformation confined on the side of the bubbles facing away from the direction of acceleration. For Bo below the critical region shape oscillations spanning the entire bubble surface take place, as a result of subharmonic resonance. The presence of the oscillatory acoustic field adds one more frequency to the system and increases the possibilities for resonance. However, only subharmonic resonance is observed because it occurs on a faster timescale, O(1/ε), where ε is the disturbance amplitude. Furthermore, among the different possible periodic variations of the volume of each bubble, the one with the smaller period determines which Legendre mode will be excited through subharmonic resonance. Spherical-cap shapes also occur on a timescale O(1/ε). When the bubbles are driven below resonance and for quite large amplitudes of the acoustic pressure, ε ≈ 0.8, a subharmonic signal at half the natural frequency of volume oscillations is obtained. This signal is primarily associated with the zeroth mode and corresponds to volume expansion followed by rapid collapse of the bubbles, a behaviour well documented in acoustic cavitation experiments.