Department of Mechanical Engineering, Indian Institute of Technology Delhi, New Delhi-110016, India
Department of Mechanical Engineering, IIT Delhi, New Delhi-110016, India
Department of Mechanical Engineering, IIT Delhi, Hauz Khas, New Delhi, 110006, India
In this article, the formation of uncharged and charged pendant droplets from a needle and their growing phenomenon concerning droplet hanging time before pinching off were experimentally investigated. The interplay of different forces like the surface tension force, gravity force, and electric force affect the stability of the pendant droplet. Experimentally it was established by varying the size of the needles (14, 18,20, 21, 22, and 27 gauge), liquid flowrate (1-10µl/min), and voltage of DC supply (0 - ±3kV). The hanging time (stability) of pendant droplets was found to be more for larger size needles in comparison with smaller needles. It was observed that with an increase in applied voltage and flowrate of water, the stability of the pendant droplet gradually decreases. The vigorous oscillation of pendant droplet was visualized for higher applied DC voltage (more than ±3kV), which states that enhancing of electrostatic force resulted in instability of pendant droplet. It was also determined that for stable pendant droplets, the Bond number (Bo) was in the range between 0.134 to 1.21.