Effect of bubble deformation on the properties of bubbly flows
Effect of bubble deformation on the properties of bubbly flows
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DOI：
10.1017/s0022112003006293
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发表时间：
2003-11
影响因子：
3.7
通讯作者：
Bernard Bunner;G. Tryggvason
中科院分区：
文献类型：
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作者：
Bernard Bunner;G. Tryggvason
对周期域内27个三维可变形浮力气泡的运动进行了直接数值模拟。完整的Navier-Stokes方程通过并行有限差分/前沿跟踪方法求解，该方法允许气泡和悬浮流体之间的可变形界面和表面张力的夹杂。取EöTVöS数为5，气泡为椭球体，伽利略数为900时，无界流中单个气泡的上升雷诺数约为26。研究了空泡率的三个取值：2%、6%和12%。在6%时，可以观察到气泡行为的变化。气泡在整个流场中分布均匀，平均上升雷诺数为23。气泡上升约90个气泡直径后，它们形成一股垂直流并加速。对气泡悬浮液的微观结构进行了分析，并对气泡悬浮液的形成提出了解释。椭球气泡的结果与近球形气泡的结果进行了比较，近球形气泡的EötvöS数为1，伽利略数为900.分析了气泡在液相中的弥散和速度脉动。
Direct numerical simulations of the motion of 27 three-dimensional deformable buoyant bubbles in periodic domains are presented. The full Navier–Stokes equations are solved by a parallelized finite-difference/front-tracking method that allows a deformable interface between the bubbles and the suspending fluid and the inclusion of surface tension. The Eötvös number is taken as equal to 5, so that the bubbles are ellipsoidal, and the Galileo number is 900, so that the rise Reynolds number of a single bubble in an unbounded flow is about 26. Three values of the void fraction have been investigated: 2%, 6% and 12%. At 6%, a change in the behaviour of the bubbles is observed. The bubbles are initially dispersed homogeneously throughout the flow field and their average rise Reynolds number is 23. After the bubbles have risen by about 90 bubble diameters, they form a vertical stream and accelerate. The microstructure of the bubble suspension is analysed and an explanation is proposed for the formation of these streams. The results for the ellipsoidal bubbles are compared to the results for nearly spherical bubbles, for which the Eötvös number is 1 and the Galileo number is 900. The dispersion of the bubbles and the velocity fluctuations in the liquid phase are analysed.