The role of surface tension in microgravity slug flow
The role of surface tension in microgravity slug flow
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DOI：
10.1016/0009-2509(95)00320-7
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发表时间：
1996-03
影响因子：
4.7
通讯作者：
Y. Taitel;L. Witte
中科院分区：
文献类型：
--
作者：
Y. Taitel;L. Witte
在重力条件下的段塞流分析中，通常忽略表面张力。液塞被视为均匀混合物，并且在液塞后面的泰勒气泡区中与壁相邻的液膜使用一维方法（通道流理论）进行处理。尽管使用一维方法并不准确，尤其是在接近泡罩的地方，但它被认为是一种有效的近似，并且它为段塞流中的压降、气泡长度和空隙率的建模提供了合理的结果。由于对于微重力流的情况，表面张力预计将成为不容忽视的主导力，因此人们可能会倾向于使用相同的程序来分析微重力条件下的段塞流，其中包括表面张力（对于非微重力条件也可以这样做）。在这项工作中，结果表明，在薄膜分析的一维方法中包含表面张力会导致泡罩附近出现错误且不可接受的结果，甚至无法用作近似值。还表明，远离盖子的情况下，具有和不具有表面张力的溶液实际上是相同的。因此，提出了微重力下段塞流的简化模型，该模型假设鼻子处的气泡呈球形，与下游下游的传统一维粘性溶液相匹配。在此过程中，实际上通过施加球冠间接考虑了鼻子处表面张力的影响。也就是说，假设气泡鼻的行为类似于受表面张力控制的小尺寸气泡的行为。
In the analysis of slug flow under gravity conditions surface tension is usually neglected. The liquid slug is treated as a homogeneous mixture and the liquid film adjacent to the wall, in the Taylor bubble zone behind the slug, is treated using the one-dimensional approach (channel flow theory). Although the use of the one-dimensional approach is not accurate, especially close to the bubble cap, it is considered as a valid approximation and it yields reasonable results for the modeling of pressure drop, bubble length and void fraction in slug flow. Since for the case of microgravity flow, surface tension is expected to be a dominant force that should not be overlooked, one may be tempted to use the same procedure for the analysis of slug flow under microgravity conditions with the surface tension included (this can be done also for non-microgravity conditions). In this work, it is shown that the inclusion of the surface tension in the one-dimensional approach for the film analysis leads to erroneous and unacceptable results near the bubble cap that cannot be used even as an approximation. It is also shown that far away from the cap the solution with and without the surface tension is practically the same. Thus, a simplified model for slug flow in microgravity is suggested that assumes a spherical shape of the bubbles at the nose that is matched with the conventional one-dimensional viscous solution far downstream. In this procedure the effect of surface tension at the nose is in fact taken into account indirectly by the imposition of a spherical cap. That is, the assumption that the bubble nose behaves similar to the behavior of small size bubbles that are controlled by surface tension.