Study of the quasi-static motion of a droplet expelled from a pipe in microgravity

In this paper, a theoretical and numerical study of the quasi-static motion of a large droplet pushed out of a pipe in microgravity environment was presented. For the existence of surface force, an external force is needed to push the droplet out of the pipe. Methods to calculate the external force, the surface force, and the pressure drops were established in theoretical model and numerical simulation, respectively. The changes of the free energy, the surface force, as well as the pressure drops during a droplet being pushed out of a pipe were discussed in this work. The surface force reaches its maximal value, when the radii of upside contact line equals to the radius of the pipe. At last, a comparison of the two methods was made based on the results.