Electrohydrodynamic analysis of bubble burst in large Leidenfrost droplets
Electrohydrodynamic analysis of bubble burst in large Leidenfrost droplets
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DOI：
10.1063/5.0029106
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发表时间：
2020-12
影响因子：
4.6
通讯作者：
O. Ozkan;V. Bahadur
中科院分区：
文献类型：
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作者：
O. Ozkan;V. Bahadur
在足够热的表面上，液滴下方会形成薄薄的蒸汽间隙，从而阻止固液接触（莱顿弗罗斯特效应）。通过在蒸气隙上施加电势差以静电抑制莱顿弗罗斯特态，可以部分消除该蒸气隙。莱顿弗罗斯特液滴中可能发生的一个有趣的与流体动力学相关的现象是蒸汽圆顶的形成以及随后在液滴中心的气泡破裂。这项工作报告了在电场影响下莱顿弗罗斯特大液滴中蒸气穹形成和气泡破裂的综合研究。首先，开发了详细的数值模型（非线性薄膜润滑方程）来分析蒸汽穹顶和气泡破裂的演变。其次，进行简化的稳定性分析，以分析估计电场影响下的临界液滴直径（气泡破裂）。第三，进行实验测量电场影响下莱顿弗罗斯特液滴气泡破裂的临界直径。数值模拟和稳定性分析的结果与实验测量结果非常吻合。气泡破裂的临界直径和连续蒸汽破裂之间的时间间隔随着施加的电场而减小。对目前研究的蒸气爆裂和薄膜沸腾进行了比较；潜在流体动力学现象的相似性导致气泡破裂的长度和时间尺度与薄膜沸腾中遇到的相似。
A thin vapor gap forms underneath a liquid drop on a sufficiently hot surface, which prevents solid–liquid contact (the Leidenfrost effect). This vapor gap can be partly eliminated by applying an electrical potential difference across the vapor gap to electrostatically suppress the Leidenfrost state. An interesting hydrodynamics-related phenomenon that can occur in Leidenfrost droplets is the formation of a vapor dome and subsequent bubble burst at the center of the droplet. This work reports a comprehensive study of vapor dome formation and bubble burst in large Leidenfrost droplets under the influence of an electric field. First, a detailed numerical model (non-linear thin film lubrication equation) is developed to analyze the evolution of the vapor dome and bubble burst. Second, a simplified stability analysis is conducted to analytically estimate the critical droplet diameter (for bubble burst) under the influence of an electric field. Third, experiments are conducted to measure the critical diameter of Leidenfrost droplets for bubble burst under the influence of electric fields. The results from the numerical modeling and stability analysis show very good agreement with experimental measurements. The critical diameter for bubble burst and the time period between consecutive vapor bursts reduce with the applied electric field. Comparisons are made between the presently studied vapor burst and film boiling; similarity in the underlying hydrodynamic phenomena results in the length and time scales for bubble burst being similar to those encountered in film boiling.