Experimental study of the movement and morphological characteristics of droplet flow between horizontal tubes

The process of low-velocity water droplets falling over a significant distance between horizontal tubes was observed by a high-speed camera. Several novel features were characterized and analyzed. The droplets were identified as primary and satellite droplets. The droplet falling behavior under varying flow rates was examined. Based on the innovative discovery that both the initial droplet diameter and its falling velocity before detachment follow linear laws, empirical formulas for the primary droplet diameter and falling velocity were developed. The formation and evolution of satellite droplets were described in detail, and their deformation was analyzed. Additionally, the volume and surface area of both the detached droplet and the satellite droplets were measured. The results indicate that the flow pattern of low-velocity droplets between widely spaced horizontal tubes is characterized by intermittent droplet flow. As the flow rate increases, the detachment length also increases. The detached droplet serves a dominant function within the droplet flow, transporting the majority of the liquid in the falling droplet. There is a linear relationship between droplet falling velocity and the falling distance before detachment from the neck. The amplitude and period of the deformation oscillation of the satellite droplets decrease over time, ultimately resulting in the droplets tending toward a spherical shape.