arXiv 2310.185302023-10-27physics.flu-dyn

气体密度影响微流体射流冲击深水池时从毛细管坍塌到表面密封的转变

Gas density influences the transition from capillary collapse to surface seal in microfluidic jet impacts on deep pools

Thijmen B. Kroeze, David Fernandez Rivas, Miguel A. Quetzeri-Santiago

AI总结：

本文通过Basilisk C数值模拟研究了射流冲击深水池时气体密度和韦伯数对空腔坍塌机制的影响，揭示了毛细管主导的深层密封与气体夹带主导的表面密封两种状态，并给出了基于韦伯数的标度关系。

摘要：

液体射流冲击深液体池的研究对于众多工程和环境应用具有重要意义。在射流冲击过程中，池的自由表面发生变形并产生空腔。同时，空腔的自由表面沿径向向外扩展并形成边缘。最终，空腔在气体惯性和表面张力的作用下坍塌。在这项工作中，我们在不同的冲击速度和环境气体密度条件下对这种空腔坍塌进行了数值研究。在Basilisk C中构建了一个基于流体体积法的轴对称数值模型。该模型在先前未被探索的参数范围内，通过与理论和实验的定性和定量比较进行了验证。我们的结果显示了空腔坍塌机制中的两种不同状态。通过考虑沿界面拉动的力，我们基于韦伯数推导出了空腔闭合时间和最大半径的标度关系。对于从尖端到尾部具有均匀恒定速度且$We \leq 150$的射流，空腔闭合由毛细管主导，并发生在表面以下（深层密封）。相比之下，对于$We \geq 200$，空腔闭合发生在表面以上（表面密封），并由气体夹带及其引起的压力梯度主导。我们的结果为理解液滴撞击大型水体时的污染物输运以及其他工程应用（如增材制造、光刻和无针注射）提供了信息。

英文摘要：

Studies of liquid jet impacts onto a deep liquid pool are of great significance for a multitude of engineering and environmental applications. During jet impact, the free surface of the pool deforms and a cavity is generated. Simultaneously, the free surface of the cavity extends radially outward and forms a rim. Eventually the cavity collapses by means of gas inertia and surface tension. In this work we study numerically such cavity collapse, under different impact velocities and ambient gas density conditions. An axisymmetric numerical model, based on the volume of fluid method is constructed in Basilisk C. This model is validated by qualitative and quantitative comparison with theory and experiments, in a parameter range that has not been previously explored. Our results show two distinct regimes in the cavity collapse mechanism. By considering forces pulling along the interface, we derive scaling arguments for the time of closure and maximum radius of the cavity, based on the Weber number. For jets with uniform constant velocity from tip to tail and $We \leq 150$ the cavity closure is capillary dominated and happens below the surface (deep seal). In contrast, for $We \geq 200$ the cavity closure happens above the surface (surface seal) and is dominated by the gas entrainment and the pressure gradient that it causes. Our results provide information for understanding pollutant transport during droplet impacts on large bodies of water, and other engineering application, like additive manufacturing, lithography and needle-free injections.

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