Direct Numerical Simulation of Bubble Formation Through a Submerged “Flute” With Experimental Validation
Direct Numerical Simulation of Bubble Formation Through a Submerged “Flute” With Experimental Validation
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DOI：
10.1115/1.4052051
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发表时间：
2022-02
影响因子：
2
通讯作者：
N. Pillai;N. Sponsel;K. Stapelmann;I. Bolotnov
中科院分区：
文献类型：
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作者：
N. Pillai;N. Sponsel;K. Stapelmann;I. Bolotnov
直接数值模拟（DNS）通常用于揭示和突出使用其他计算流体动力学方法无法正确解决的物理现象，因为后者为了降低计算成本而采取了捷径。在这项工作中，我们使用DNS沿着与接口跟踪，以深入了解气泡的形成，离开，并通过水上升。为了形成气泡，空气通过一种新颖的孔几何形状注入，与淹没在水下的长笛不同，这引入了在传统孔研究中通常不被发现的现象。例如，我们的单相模拟显示出显著的倾斜效应，其中在尾喷嘴边缘处积聚的压力导致通过喷嘴孔的不对称排放以及管道其余部分中的流动的向上偏置。在我们的两相模拟中，这种效应被喷嘴上气泡的表面张力所掩盖，但在离开事件之后仍然可以看到。气泡离开后，我们观察到气泡向椭圆体形状收敛，这一点已被实验验证。随着气泡的上升，我们注意到，垂直速度的局部变化会导致气泡边缘轻微摆动，在边缘处的相对较低和较高的速度之间振荡。
Direct numerical simulation (DNS) is often used to uncover and highlight physical phenomena that are not properly resolved using other computational fluid dynamics methods due to shortcuts taken in the latter to cheapen computational cost. In this work, we use DNS along with interface tracking to take an in-depth look at bubble formation, departure, and ascent through water. To form the bubbles, air is injected through a novel orifice geometry not unlike that of a flute submerged underwater, which introduces phenomena that are not typically brought to light in conventional orifice studies. For example, our single-phase simulations show a significant leaning effect, wherein pressure accumulating at the trailing nozzle edges leads to asymmetric discharge through the nozzle hole and an upward bias in the flow in the rest of the pipe. In our two-phase simulations, this effect is masked by the surface tension of the bubble sitting on the nozzle, but it can still be seen following departure events. After bubble departure, we observe the bubbles converge toward an ellipsoidal shape, which has been validated by experiments. As the bubbles rise, we note that local variations in the vertical velocity cause the bubble edges to flap slightly, oscillating between relatively low and high velocities at the edges.