Outer ligament-mediated spray formation of annular liquid sheet by an inner round air stream

The interfacial jetting phenomena of coaxial air-assisted water jets are studied using high-speed digital camera. Here, an inner round air jet is injected into annular water sheet spray. The experimental photographs show that the outside interface of liquid sheet shoots out large numbers of violent ligaments at high air velocity. The ligament velocity, ligament angle, ligament diameter, fragment size, and distribution are measured and analyzed. There are two kinds of ligament evolution that are breakup and contraction. An empirical model is also proposed for the ligament evolution process. At last, we obtain the criterion of critical Weber number on the ligament breakup based on the experimental results. This suggestion agrees well with the experimental data.