Nonlinear oscillations of gas bubbles submerged in water: implications for plasma breakdown
Nonlinear oscillations of gas bubbles submerged in water: implications for plasma breakdown
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DOI：
10.1088/0022-3727/45/41/415203
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发表时间：
2012-10
期刊：
影响因子：
--
通讯作者：
B. Sommers;J. Foster
中科院分区：
文献类型：
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作者：
B. Sommers;J. Foster
浸没在电介质液体中并由电场驱动的气泡可以经历形状和体积的急剧变化。在某些情况下，这种变形可以增强气泡内部的外加场分布，并降低内部气体压力。这两种效应将倾向于促进气体体积中的等离子体形成。这两种效应的实际实现可能对液体等离子体技术的可行性产生广泛的影响，液体等离子体技术往往受到高电压要求的影响。在该实验中，直径为0.4-0.7 mm的气泡悬浮在26.4 kHz的水声驻波的波节中，并使用振幅为5-15 kV cm-1的交流电场激发成非线性形状的振荡。变形气泡的振动用以5130帧s-1操作的高速相机拍摄，并且使用边缘检测算法将所得图像分解成它们的轴对称球谐模式。总的来说，气泡运动由前三个偶模l = 0、2和4主导。变形的气泡的内部电场的静电模拟表明，所施加的场被增强高达2.3以上的标称施加的字段的一个因素。对纯l = 2和l = 4模式的进一步模拟预测，在附加变形的情况下，场增强因子可以达到多达10-50。
Gas bubbles submerged in a dielectric liquid and driven by an electric field can undergo dramatic changes in both shape and volume. In certain cases, this deformation can enhance the distribution of the applied field inside the bubble as well as decrease the internal gas pressure. Both effects will tend to facilitate plasma formation in the gas volume. A practical realization of these two effects could have a broad impact on the viability of liquid plasma technologies, which tend to suffer from high voltage requirements. In this experiment, bubbles of diameter 0.4–0.7 mm are suspended in the node of a 26.4 kHz underwater acoustic standing wave and excited into nonlinear shape oscillations using ac electric fields with amplitudes of 5–15 kV cm−1. Oscillations of the deformed bubble are photographed with a high-speed camera operating at 5130 frames s−1 and the resulting images are decomposed into their axisymmetric spherical harmonic modes, , using an edge detection algorithm. Overall, the bubble motion is dominated by the first three even modes l = 0, 2 and 4. Electrostatic simulations of the deformed bubble's internal electric field indicate that the applied field is enhanced by as much as a factor of 2.3 above the nominal applied field. Further simulation of both the pure l = 2 and l = 4 modes predicts that with additional deformation, the field enhancement factors could reach as much as 10–50.