Spatial modes of capillary jets, with application to surface stimulation
Spatial modes of capillary jets, with application to surface stimulation
复制标题
毛细管射流的空间模式，及其在表面刺激中的应用
DOI：
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发表时间：
2012
影响因子：
3.7
通讯作者：
F. J. García
中科院分区：
文献类型：
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作者：
Josefa Guerrero;H. González;F. J. García
任何物理来源的表面刺激（电流体动力学，热毛细等）其目的是在自由表面或毛细管射流的速度场上产生局部扰动。在这些扰动中，只有轴对称扰动是射流破碎的决定因素。通常情况下，刺激是足够弱的线性模型适用。然后，刺激可以通过用于应力的绿色函数来描述，垂直于界面和切向于界面，另外，其计算与流体动力学变量解耦。如果应用谐波强迫，这些绿色函数是空间模式的组合，其相关极点位于复波数平面的适当积分轮廓内。这是一个全面的枚举和描述的空间模式，这还没有做到现在的动机。模式熟悉的时间分析，占主导地位的和次主导地位的毛细管模式和水动力模式，存在，沿着模式特定的空间分析。后者的大多数已经在无粘射流的文献中提到过，但没有分析过。报告以前未找到的模式。此外，与每种模式相关联的速度场的描述，作为一种工具，以了解他们的物理起源和行为。每个模式在正常和切向应力刺激的相对重要性进行了讨论。最后，著名的合并极点低于临界射流速度，导致绝对不稳定，分析了在光的模态描述。
Abstract Surface stimulation of any physical origin (electrohydrodynamic, thermocapillary, etc.) has the goal of generating localized perturbations on the free surface or the velocity field of a capillary jet. Among these perturbations, only the axisymmetric ones are determinant for the jet breakup. Often, the stimulation is weak enough for a linear model to be applicable. Then, the stimulation can be described by means of the Green functions for stresses, both normal and tangential to the interface, the calculations of which are, in addition, uncoupled from the hydrodynamic variables. If a harmonic forcing is applied, these Green functions are combinations of the spatial modes whose associated poles lie inside the appropriate integration contour of the complex wavenumber plane. This is the motivation for a comprehensive enumeration and description of the spatial modes, which has not been done up to now. Modes familiar from a temporal analysis, the dominant and subdominant capillary modes and the hydrodynamic modes, are present, along with modes specific to a spatial analysis. Most of the latter have already been mentioned in the literature for inviscid jets, but not analysed. A mode not previously found is reported. In addition, a description of the velocity field associated with each mode is provided, as a tool to understand their physical origin and behaviour. The relative importance of each mode in both normal- and tangential-stress stimulations is discussed. Finally, the well-known merging of poles below a critical jet velocity, leading to absolute instability, is analysed in the light of the modal description.