Excitation of airwaves caused by bubble bursting in a cylindrical conduit : Experiments and a model
Excitation of airwaves caused by bubble bursting in a cylindrical conduit : Experiments and a model
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圆柱形导管中气泡破裂引起的电波激发：实验和模型
DOI：
10.1029/2009jb006828
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
& I. Sumita
中科院分区：
文献类型：
--
作者：
T. Kobayashi;A. Namiki;& I. Sumita
斯特龙博利火山爆发被认为是一个大气泡破裂的结果。为了了解气泡破裂的方式与产生的空气波之间的关系，我们进行了实验的气泡破裂的粘性液体的表面的顶部包含在丙烯酸管作为空气柱，并观察它的视觉和听觉。我们发现当液体粘度小于1Pa·s时，气泡在破裂前是振动的。气泡破裂过程中空气波的主要来源是气泡的振动。另一方面，当液体粘度大于1Pa·s时，气泡不振动。在气泡破裂期间，气泡膜上出现孔。孔径的增长先加速，然后减速，最后停止。空气波的主要来源是孔径增长。我们计算了孔径生长产生的空气波的合成波形，很好地解释了实验观察到的空气波。当由孔径增长产生的空气波的频率与空气柱的本征频率匹配时，发生共振。将此模型应用于Strombolian喷发，当孔径增长速度为每秒数米时，解释了特征低频（<20 Hz）。该模型还解释了在斯特龙博利火山爆发中观察到的空气波的不对称初始上升，作为孔径加速增长的结果。
Strombolian eruptions are considered to be a consequence of the bursting of a large bubble. In order to understand the relation between the style of bubble bursting and the resulting airwave, we perform experiments of bubble bursting at the top of the surface of viscous liquid contained in an acrylic pipe which acts as an air column and observe it visually and acoustically. We find that when the liquid viscosity is less than 1 Pa s, the bubble vibrates before bursting. The major source of the airwave during the sequence of the bubble bursting is the bubble vibration. On the other hand, when the liquid viscosity is greater than 1 Pa s, the bubble does not vibrate. During bubble bursting, an aperture appears on the bubble film. The aperture growth first accelerates and later decelerates before finally stopping. The major source of the airwave is the aperture growth. We calculate a synthetic waveform of the airwave generated by the aperture growth which explains the experimentally observed airwave well. When the frequency of the airwave generated by the aperture growth matches the eigenfrequency of the air column, resonance occurs. Applying this model to the Strombolian eruption, the characteristic low frequency (<20 Hz) is explained if the velocity of the aperture growth is several meters per second. The model also explains the asymmetrical initial rise of the airwave observed in the Strombolian eruptions as a result of the accelerating growth of the aperture.