Numerical modeling of oscillating Taylor bubbles
Numerical modeling of oscillating Taylor bubbles
复制标题
DOI：
10.1080/19942060.2016.1224737
复制
发表时间：
2016-01
影响因子：
6.1
通讯作者：
S. Ambrose;D. Hargreaves;I. Lowndes
中科院分区：
文献类型：
--
作者：
S. Ambrose;D. Hargreaves;I. Lowndes
摘要本文采用计算流体动力学（CFD）方法模拟了泰勒气泡在垂直管道中的上升过程。实验表明，在用于空气-水系统的大直径（0.29 m）管道中，气泡可以以振荡方式上升，这取决于空气注入的方法。CFD模型能够捕捉这种振荡行为，因为空气相被建模为可压缩的理想气体。深入了解收缩和膨胀过程中的气泡前后的流场。对于一个初始压力等于其头部流体静压的气泡，当气泡上升时，在气泡中没有看到振荡。如果气泡中的初始压力被设定为小于或大于流体静压力，则气泡的长度以取决于初始气泡压力相对于流体静压力的大小的幅度振荡。振荡的频率与气泡上方的水头的平方根成反比，因此频率随着气泡接近水面而增加。预测的频率还取决于平均气泡长度的平方根成反比，与实验观察和分析模型，也提出了一致。在该模型中，由于存在的斯托克斯边界层的振荡情况下的粘性阻尼项被引入的第一次，并用于评估增加液体粘度的几个数量级的振荡上的效果。
ABSTRACT In this study, computational fluid dynamics (CFD) modeling is used to simulate Taylor bubbles rising in vertical pipes. Experiments indicate that in large diameter (0.29 m) pipes for an air–water system, the bubbles can rise in a oscillatory manner, depending on the method of air injection. The CFD models are able to capture this oscillatory behavior because the air phase is modeled as a compressible ideal gas. Insights into the flow field ahead and behind the bubble during contraction and expansion are shown. For a bubble with an initial pressure equal to the hydrostatic pressure at its nose, no oscillations are seen in the bubble as it rises. If the initial pressure in the bubble is set less than or greater than the hydrostatic pressure then the length of the bubble oscillates with an amplitude that depends on the magnitude of the initial bubble pressure relative to the hydrostatic pressure. The frequency of the oscillations is inversely proportional to the square root of the head of water above the bubble and so the frequency increases as the bubble approaches the water surface. The predicted frequency also depends inversely on the square root of the average bubble length, in agreement with experimental observations and an analytical model that is also presented. In this model, a viscous damping term due to the presence of a Stokes boundary layer for the oscillating cases is introduced for the first time and used to assess the effect on the oscillations of increasing the liquid viscosity by several orders of magnitude.