Electrohydrostatics of pendant drops in a direct current electric field

Whereas electrified pendant drops between a parallel-plate capacitor have been well studied, electrohydrostatics of pendant drops coaxial with a disk electrode have not been reported to date. In this research, axisymmetric equilibrium shapes and stability of a perfectly conductive drop hanging from a rod that is coaxial with a circular disk electrode between two electrically grounded parallel plates were studied. Results showed that elongation along axis of symmetry (EAAS) and depression along axis of symmetry (DAAS) shape families can be observed as equilibrium profiles at the stability limit for an electrified drop of constant volume. The largest charge density on an EAAS drop at the stability limit is located at the tip of the drop; whereas the largest charge density on an DAAS drop at the stability limit is located at the side of the drop. The electric field strength needed to breakup the drop is much smaller for a DAAS drop than an EAAS drop.; The effect of electrode configuration, gravity and drop size on the evolution of electrified pendant drops was surveyed. The theoretical results generated by Boundary Integral (BI) approach and Domain Differential (DD) approach were compared. Experiment was performed to verify theoretical computations. The conical tip at the stability limit of an EAAS drop was observed. The spray from the side for a DAAS drop after breakup was evidenced.