  Soap bubbles can be easily generated by varies methods, while their formation
process is complicated and still worth study. A model about the bubble
formation process was proposed in Phys. Rev. Lett. 116, 077801 recently, and it
was reported that the bubbles were formed when the gas blowing velocity was
above one threshold. However, after repeating these experiments, we found the
bubbles could be generated in two velocities ranges which corresponded to
laminar and turbulent gas jet respectively, and the predicted threshold was
only effective for turbulent gas flow. The study revealed that the bubble
formation was mainly influenced by the aerodynamics of the gas jet blowing to
the film, and these results will help to further understand the formation
mechanism of the soap bubble as well as the interaction between gas jet and
thin liquid film.
