Armstrong Liquid Bridge: Formation, Evolution and Breakup

TL;DR

This study experimentally investigates the formation, evolution, and breakup of Armstrong liquid bridges, revealing the critical role of effective length and electric field, and providing a simplified model to explain the breakup mechanism.

Contribution

The paper introduces a simplified electrified jet model and linear stability analysis to explain the breakup of liquid bridges, linking effective length with electric field and external flow effects.

Findings

Breakup occurs when effective length reaches a threshold.

Effective length increases linearly with applied voltage.

External flow controls the lifetime but not the breakup length.

Abstract

In this paper, we experimentally explore the formation, evolution and breakup of Armstrong liquid bridge. The extremely complicated evolution stage is revealed, which involves many coupled processes including the morphology change, current variation, heat transfer, and water evaporation. By focusing on the final fate of this liquid bridge, we observe that the breakup occurs once an effective length ($\tilde{L}$) is reached. This effective length increases linearly with the applied voltage, implying a threshold electric field to sustain the liquid bridge. Moreover, by an introduced external flow, the lifetime of the liquid bridge can be controlled, while the effective length associated with the breakup is independent on the external flow rate. Hence, these findings remarkably demonstrate that the breakup of liquid bridge is directly correlated with the effective length. In order to understand this correlation, a simplified model of an electrified jet is employed to take the electric field into account. By the linear stability analysis, the attained phase diagram agrees with the experiments well. Although a more comprehensive theory is required to consider other factors such as the surface charges, these results might provide a fresh perspective on the ``century-old" Armstrong liquid bridge to further elucidate its underlying physical mechanism.